1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * bpf_jit_comp.c: BPF JIT compiler
4 *
5 * Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com)
6 * Internal BPF Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
7 */
8 #include <linux/netdevice.h>
9 #include <linux/filter.h>
10 #include <linux/if_vlan.h>
11 #include <linux/bpf.h>
12 #include <linux/memory.h>
13 #include <linux/sort.h>
14 #include <asm/extable.h>
15 #include <asm/set_memory.h>
16 #include <asm/nospec-branch.h>
17 #include <asm/text-patching.h>
18
emit_code(u8 * ptr,u32 bytes,unsigned int len)19 static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
20 {
21 if (len == 1)
22 *ptr = bytes;
23 else if (len == 2)
24 *(u16 *)ptr = bytes;
25 else {
26 *(u32 *)ptr = bytes;
27 barrier();
28 }
29 return ptr + len;
30 }
31
32 #define EMIT(bytes, len) \
33 do { prog = emit_code(prog, bytes, len); cnt += len; } while (0)
34
35 #define EMIT1(b1) EMIT(b1, 1)
36 #define EMIT2(b1, b2) EMIT((b1) + ((b2) << 8), 2)
37 #define EMIT3(b1, b2, b3) EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3)
38 #define EMIT4(b1, b2, b3, b4) EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4)
39
40 #define EMIT1_off32(b1, off) \
41 do { EMIT1(b1); EMIT(off, 4); } while (0)
42 #define EMIT2_off32(b1, b2, off) \
43 do { EMIT2(b1, b2); EMIT(off, 4); } while (0)
44 #define EMIT3_off32(b1, b2, b3, off) \
45 do { EMIT3(b1, b2, b3); EMIT(off, 4); } while (0)
46 #define EMIT4_off32(b1, b2, b3, b4, off) \
47 do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0)
48
is_imm8(int value)49 static bool is_imm8(int value)
50 {
51 return value <= 127 && value >= -128;
52 }
53
is_simm32(s64 value)54 static bool is_simm32(s64 value)
55 {
56 return value == (s64)(s32)value;
57 }
58
is_uimm32(u64 value)59 static bool is_uimm32(u64 value)
60 {
61 return value == (u64)(u32)value;
62 }
63
64 /* mov dst, src */
65 #define EMIT_mov(DST, SRC) \
66 do { \
67 if (DST != SRC) \
68 EMIT3(add_2mod(0x48, DST, SRC), 0x89, add_2reg(0xC0, DST, SRC)); \
69 } while (0)
70
bpf_size_to_x86_bytes(int bpf_size)71 static int bpf_size_to_x86_bytes(int bpf_size)
72 {
73 if (bpf_size == BPF_W)
74 return 4;
75 else if (bpf_size == BPF_H)
76 return 2;
77 else if (bpf_size == BPF_B)
78 return 1;
79 else if (bpf_size == BPF_DW)
80 return 4; /* imm32 */
81 else
82 return 0;
83 }
84
85 /*
86 * List of x86 cond jumps opcodes (. + s8)
87 * Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
88 */
89 #define X86_JB 0x72
90 #define X86_JAE 0x73
91 #define X86_JE 0x74
92 #define X86_JNE 0x75
93 #define X86_JBE 0x76
94 #define X86_JA 0x77
95 #define X86_JL 0x7C
96 #define X86_JGE 0x7D
97 #define X86_JLE 0x7E
98 #define X86_JG 0x7F
99
100 /* Pick a register outside of BPF range for JIT internal work */
101 #define AUX_REG (MAX_BPF_JIT_REG + 1)
102 #define X86_REG_R9 (MAX_BPF_JIT_REG + 2)
103
104 /*
105 * The following table maps BPF registers to x86-64 registers.
106 *
107 * x86-64 register R12 is unused, since if used as base address
108 * register in load/store instructions, it always needs an
109 * extra byte of encoding and is callee saved.
110 *
111 * x86-64 register R9 is not used by BPF programs, but can be used by BPF
112 * trampoline. x86-64 register R10 is used for blinding (if enabled).
113 */
114 static const int reg2hex[] = {
115 [BPF_REG_0] = 0, /* RAX */
116 [BPF_REG_1] = 7, /* RDI */
117 [BPF_REG_2] = 6, /* RSI */
118 [BPF_REG_3] = 2, /* RDX */
119 [BPF_REG_4] = 1, /* RCX */
120 [BPF_REG_5] = 0, /* R8 */
121 [BPF_REG_6] = 3, /* RBX callee saved */
122 [BPF_REG_7] = 5, /* R13 callee saved */
123 [BPF_REG_8] = 6, /* R14 callee saved */
124 [BPF_REG_9] = 7, /* R15 callee saved */
125 [BPF_REG_FP] = 5, /* RBP readonly */
126 [BPF_REG_AX] = 2, /* R10 temp register */
127 [AUX_REG] = 3, /* R11 temp register */
128 [X86_REG_R9] = 1, /* R9 register, 6th function argument */
129 };
130
131 static const int reg2pt_regs[] = {
132 [BPF_REG_0] = offsetof(struct pt_regs, ax),
133 [BPF_REG_1] = offsetof(struct pt_regs, di),
134 [BPF_REG_2] = offsetof(struct pt_regs, si),
135 [BPF_REG_3] = offsetof(struct pt_regs, dx),
136 [BPF_REG_4] = offsetof(struct pt_regs, cx),
137 [BPF_REG_5] = offsetof(struct pt_regs, r8),
138 [BPF_REG_6] = offsetof(struct pt_regs, bx),
139 [BPF_REG_7] = offsetof(struct pt_regs, r13),
140 [BPF_REG_8] = offsetof(struct pt_regs, r14),
141 [BPF_REG_9] = offsetof(struct pt_regs, r15),
142 };
143
144 /*
145 * is_ereg() == true if BPF register 'reg' maps to x86-64 r8..r15
146 * which need extra byte of encoding.
147 * rax,rcx,...,rbp have simpler encoding
148 */
is_ereg(u32 reg)149 static bool is_ereg(u32 reg)
150 {
151 return (1 << reg) & (BIT(BPF_REG_5) |
152 BIT(AUX_REG) |
153 BIT(BPF_REG_7) |
154 BIT(BPF_REG_8) |
155 BIT(BPF_REG_9) |
156 BIT(X86_REG_R9) |
157 BIT(BPF_REG_AX));
158 }
159
160 /*
161 * is_ereg_8l() == true if BPF register 'reg' is mapped to access x86-64
162 * lower 8-bit registers dil,sil,bpl,spl,r8b..r15b, which need extra byte
163 * of encoding. al,cl,dl,bl have simpler encoding.
164 */
is_ereg_8l(u32 reg)165 static bool is_ereg_8l(u32 reg)
166 {
167 return is_ereg(reg) ||
168 (1 << reg) & (BIT(BPF_REG_1) |
169 BIT(BPF_REG_2) |
170 BIT(BPF_REG_FP));
171 }
172
is_axreg(u32 reg)173 static bool is_axreg(u32 reg)
174 {
175 return reg == BPF_REG_0;
176 }
177
178 /* Add modifiers if 'reg' maps to x86-64 registers R8..R15 */
add_1mod(u8 byte,u32 reg)179 static u8 add_1mod(u8 byte, u32 reg)
180 {
181 if (is_ereg(reg))
182 byte |= 1;
183 return byte;
184 }
185
add_2mod(u8 byte,u32 r1,u32 r2)186 static u8 add_2mod(u8 byte, u32 r1, u32 r2)
187 {
188 if (is_ereg(r1))
189 byte |= 1;
190 if (is_ereg(r2))
191 byte |= 4;
192 return byte;
193 }
194
195 /* Encode 'dst_reg' register into x86-64 opcode 'byte' */
add_1reg(u8 byte,u32 dst_reg)196 static u8 add_1reg(u8 byte, u32 dst_reg)
197 {
198 return byte + reg2hex[dst_reg];
199 }
200
201 /* Encode 'dst_reg' and 'src_reg' registers into x86-64 opcode 'byte' */
add_2reg(u8 byte,u32 dst_reg,u32 src_reg)202 static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg)
203 {
204 return byte + reg2hex[dst_reg] + (reg2hex[src_reg] << 3);
205 }
206
jit_fill_hole(void * area,unsigned int size)207 static void jit_fill_hole(void *area, unsigned int size)
208 {
209 /* Fill whole space with INT3 instructions */
210 memset(area, 0xcc, size);
211 }
212
213 struct jit_context {
214 int cleanup_addr; /* Epilogue code offset */
215
216 /*
217 * Program specific offsets of labels in the code; these rely on the
218 * JIT doing at least 2 passes, recording the position on the first
219 * pass, only to generate the correct offset on the second pass.
220 */
221 int tail_call_direct_label;
222 int tail_call_indirect_label;
223 };
224
225 /* Maximum number of bytes emitted while JITing one eBPF insn */
226 #define BPF_MAX_INSN_SIZE 128
227 #define BPF_INSN_SAFETY 64
228
229 /* Number of bytes emit_patch() needs to generate instructions */
230 #define X86_PATCH_SIZE 5
231 /* Number of bytes that will be skipped on tailcall */
232 #define X86_TAIL_CALL_OFFSET 11
233
push_callee_regs(u8 ** pprog,bool * callee_regs_used)234 static void push_callee_regs(u8 **pprog, bool *callee_regs_used)
235 {
236 u8 *prog = *pprog;
237 int cnt = 0;
238
239 if (callee_regs_used[0])
240 EMIT1(0x53); /* push rbx */
241 if (callee_regs_used[1])
242 EMIT2(0x41, 0x55); /* push r13 */
243 if (callee_regs_used[2])
244 EMIT2(0x41, 0x56); /* push r14 */
245 if (callee_regs_used[3])
246 EMIT2(0x41, 0x57); /* push r15 */
247 *pprog = prog;
248 }
249
pop_callee_regs(u8 ** pprog,bool * callee_regs_used)250 static void pop_callee_regs(u8 **pprog, bool *callee_regs_used)
251 {
252 u8 *prog = *pprog;
253 int cnt = 0;
254
255 if (callee_regs_used[3])
256 EMIT2(0x41, 0x5F); /* pop r15 */
257 if (callee_regs_used[2])
258 EMIT2(0x41, 0x5E); /* pop r14 */
259 if (callee_regs_used[1])
260 EMIT2(0x41, 0x5D); /* pop r13 */
261 if (callee_regs_used[0])
262 EMIT1(0x5B); /* pop rbx */
263 *pprog = prog;
264 }
265
266 /*
267 * Emit x86-64 prologue code for BPF program.
268 * bpf_tail_call helper will skip the first X86_TAIL_CALL_OFFSET bytes
269 * while jumping to another program
270 */
emit_prologue(u8 ** pprog,u32 stack_depth,bool ebpf_from_cbpf,bool tail_call_reachable,bool is_subprog)271 static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
272 bool tail_call_reachable, bool is_subprog)
273 {
274 u8 *prog = *pprog;
275 int cnt = X86_PATCH_SIZE;
276
277 /* BPF trampoline can be made to work without these nops,
278 * but let's waste 5 bytes for now and optimize later
279 */
280 memcpy(prog, ideal_nops[NOP_ATOMIC5], cnt);
281 prog += cnt;
282 if (!ebpf_from_cbpf) {
283 if (tail_call_reachable && !is_subprog)
284 EMIT2(0x31, 0xC0); /* xor eax, eax */
285 else
286 EMIT2(0x66, 0x90); /* nop2 */
287 }
288 EMIT1(0x55); /* push rbp */
289 EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
290 /* sub rsp, rounded_stack_depth */
291 if (stack_depth)
292 EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8));
293 if (tail_call_reachable)
294 EMIT1(0x50); /* push rax */
295 *pprog = prog;
296 }
297
emit_patch(u8 ** pprog,void * func,void * ip,u8 opcode)298 static int emit_patch(u8 **pprog, void *func, void *ip, u8 opcode)
299 {
300 u8 *prog = *pprog;
301 int cnt = 0;
302 s64 offset;
303
304 offset = func - (ip + X86_PATCH_SIZE);
305 if (!is_simm32(offset)) {
306 pr_err("Target call %p is out of range\n", func);
307 return -ERANGE;
308 }
309 EMIT1_off32(opcode, offset);
310 *pprog = prog;
311 return 0;
312 }
313
emit_call(u8 ** pprog,void * func,void * ip)314 static int emit_call(u8 **pprog, void *func, void *ip)
315 {
316 return emit_patch(pprog, func, ip, 0xE8);
317 }
318
emit_jump(u8 ** pprog,void * func,void * ip)319 static int emit_jump(u8 **pprog, void *func, void *ip)
320 {
321 return emit_patch(pprog, func, ip, 0xE9);
322 }
323
__bpf_arch_text_poke(void * ip,enum bpf_text_poke_type t,void * old_addr,void * new_addr,const bool text_live)324 static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
325 void *old_addr, void *new_addr,
326 const bool text_live)
327 {
328 const u8 *nop_insn = ideal_nops[NOP_ATOMIC5];
329 u8 old_insn[X86_PATCH_SIZE];
330 u8 new_insn[X86_PATCH_SIZE];
331 u8 *prog;
332 int ret;
333
334 memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
335 if (old_addr) {
336 prog = old_insn;
337 ret = t == BPF_MOD_CALL ?
338 emit_call(&prog, old_addr, ip) :
339 emit_jump(&prog, old_addr, ip);
340 if (ret)
341 return ret;
342 }
343
344 memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
345 if (new_addr) {
346 prog = new_insn;
347 ret = t == BPF_MOD_CALL ?
348 emit_call(&prog, new_addr, ip) :
349 emit_jump(&prog, new_addr, ip);
350 if (ret)
351 return ret;
352 }
353
354 ret = -EBUSY;
355 mutex_lock(&text_mutex);
356 if (memcmp(ip, old_insn, X86_PATCH_SIZE))
357 goto out;
358 ret = 1;
359 if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
360 if (text_live)
361 text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
362 else
363 memcpy(ip, new_insn, X86_PATCH_SIZE);
364 ret = 0;
365 }
366 out:
367 mutex_unlock(&text_mutex);
368 return ret;
369 }
370
bpf_arch_text_poke(void * ip,enum bpf_text_poke_type t,void * old_addr,void * new_addr)371 int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
372 void *old_addr, void *new_addr)
373 {
374 if (!is_kernel_text((long)ip) &&
375 !is_bpf_text_address((long)ip))
376 /* BPF poking in modules is not supported */
377 return -EINVAL;
378
379 return __bpf_arch_text_poke(ip, t, old_addr, new_addr, true);
380 }
381
382 #define EMIT_LFENCE() EMIT3(0x0F, 0xAE, 0xE8)
383
emit_indirect_jump(u8 ** pprog,int reg,u8 * ip)384 static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
385 {
386 u8 *prog = *pprog;
387 int cnt = 0;
388
389 #ifdef CONFIG_RETPOLINE
390 if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
391 EMIT_LFENCE();
392 EMIT2(0xFF, 0xE0 + reg);
393 } else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {
394 emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip);
395 } else
396 #endif
397 EMIT2(0xFF, 0xE0 + reg);
398
399 *pprog = prog;
400 }
401
emit_return(u8 ** pprog,u8 * ip)402 static void emit_return(u8 **pprog, u8 *ip)
403 {
404 u8 *prog = *pprog;
405 int cnt = 0;
406
407 if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {
408 emit_jump(&prog, &__x86_return_thunk, ip);
409 } else {
410 EMIT1(0xC3); /* ret */
411 if (IS_ENABLED(CONFIG_SLS))
412 EMIT1(0xCC); /* int3 */
413 }
414
415 *pprog = prog;
416 }
417
418 /*
419 * Generate the following code:
420 *
421 * ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ...
422 * if (index >= array->map.max_entries)
423 * goto out;
424 * if (++tail_call_cnt > MAX_TAIL_CALL_CNT)
425 * goto out;
426 * prog = array->ptrs[index];
427 * if (prog == NULL)
428 * goto out;
429 * goto *(prog->bpf_func + prologue_size);
430 * out:
431 */
emit_bpf_tail_call_indirect(u8 ** pprog,bool * callee_regs_used,u32 stack_depth,u8 * ip,struct jit_context * ctx)432 static void emit_bpf_tail_call_indirect(u8 **pprog, bool *callee_regs_used,
433 u32 stack_depth, u8 *ip,
434 struct jit_context *ctx)
435 {
436 int tcc_off = -4 - round_up(stack_depth, 8);
437 u8 *prog = *pprog, *start = *pprog;
438 int cnt = 0, offset;
439
440 /*
441 * rdi - pointer to ctx
442 * rsi - pointer to bpf_array
443 * rdx - index in bpf_array
444 */
445
446 /*
447 * if (index >= array->map.max_entries)
448 * goto out;
449 */
450 EMIT2(0x89, 0xD2); /* mov edx, edx */
451 EMIT3(0x39, 0x56, /* cmp dword ptr [rsi + 16], edx */
452 offsetof(struct bpf_array, map.max_entries));
453
454 offset = ctx->tail_call_indirect_label - (prog + 2 - start);
455 EMIT2(X86_JBE, offset); /* jbe out */
456
457 /*
458 * if (tail_call_cnt > MAX_TAIL_CALL_CNT)
459 * goto out;
460 */
461 EMIT2_off32(0x8B, 0x85, tcc_off); /* mov eax, dword ptr [rbp - tcc_off] */
462 EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
463
464 offset = ctx->tail_call_indirect_label - (prog + 2 - start);
465 EMIT2(X86_JA, offset); /* ja out */
466 EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
467 EMIT2_off32(0x89, 0x85, tcc_off); /* mov dword ptr [rbp - tcc_off], eax */
468
469 /* prog = array->ptrs[index]; */
470 EMIT4_off32(0x48, 0x8B, 0x8C, 0xD6, /* mov rcx, [rsi + rdx * 8 + offsetof(...)] */
471 offsetof(struct bpf_array, ptrs));
472
473 /*
474 * if (prog == NULL)
475 * goto out;
476 */
477 EMIT3(0x48, 0x85, 0xC9); /* test rcx,rcx */
478
479 offset = ctx->tail_call_indirect_label - (prog + 2 - start);
480 EMIT2(X86_JE, offset); /* je out */
481
482 pop_callee_regs(&prog, callee_regs_used);
483
484 EMIT1(0x58); /* pop rax */
485 if (stack_depth)
486 EMIT3_off32(0x48, 0x81, 0xC4, /* add rsp, sd */
487 round_up(stack_depth, 8));
488
489 /* goto *(prog->bpf_func + X86_TAIL_CALL_OFFSET); */
490 EMIT4(0x48, 0x8B, 0x49, /* mov rcx, qword ptr [rcx + 32] */
491 offsetof(struct bpf_prog, bpf_func));
492 EMIT4(0x48, 0x83, 0xC1, /* add rcx, X86_TAIL_CALL_OFFSET */
493 X86_TAIL_CALL_OFFSET);
494 /*
495 * Now we're ready to jump into next BPF program
496 * rdi == ctx (1st arg)
497 * rcx == prog->bpf_func + X86_TAIL_CALL_OFFSET
498 */
499 emit_indirect_jump(&prog, 1 /* rcx */, ip + (prog - start));
500
501 /* out: */
502 ctx->tail_call_indirect_label = prog - start;
503 *pprog = prog;
504 }
505
emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor * poke,u8 ** pprog,u8 * ip,bool * callee_regs_used,u32 stack_depth,struct jit_context * ctx)506 static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
507 u8 **pprog, u8 *ip,
508 bool *callee_regs_used, u32 stack_depth,
509 struct jit_context *ctx)
510 {
511 int tcc_off = -4 - round_up(stack_depth, 8);
512 u8 *prog = *pprog, *start = *pprog;
513 int cnt = 0, offset;
514
515 /*
516 * if (tail_call_cnt > MAX_TAIL_CALL_CNT)
517 * goto out;
518 */
519 EMIT2_off32(0x8B, 0x85, tcc_off); /* mov eax, dword ptr [rbp - tcc_off] */
520 EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
521
522 offset = ctx->tail_call_direct_label - (prog + 2 - start);
523 EMIT2(X86_JA, offset); /* ja out */
524 EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
525 EMIT2_off32(0x89, 0x85, tcc_off); /* mov dword ptr [rbp - tcc_off], eax */
526
527 poke->tailcall_bypass = ip + (prog - start);
528 poke->adj_off = X86_TAIL_CALL_OFFSET;
529 poke->tailcall_target = ip + ctx->tail_call_direct_label - X86_PATCH_SIZE;
530 poke->bypass_addr = (u8 *)poke->tailcall_target + X86_PATCH_SIZE;
531
532 emit_jump(&prog, (u8 *)poke->tailcall_target + X86_PATCH_SIZE,
533 poke->tailcall_bypass);
534
535 pop_callee_regs(&prog, callee_regs_used);
536 EMIT1(0x58); /* pop rax */
537 if (stack_depth)
538 EMIT3_off32(0x48, 0x81, 0xC4, round_up(stack_depth, 8));
539
540 memcpy(prog, ideal_nops[NOP_ATOMIC5], X86_PATCH_SIZE);
541 prog += X86_PATCH_SIZE;
542
543 /* out: */
544 ctx->tail_call_direct_label = prog - start;
545
546 *pprog = prog;
547 }
548
bpf_tail_call_direct_fixup(struct bpf_prog * prog)549 static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
550 {
551 struct bpf_jit_poke_descriptor *poke;
552 struct bpf_array *array;
553 struct bpf_prog *target;
554 int i, ret;
555
556 for (i = 0; i < prog->aux->size_poke_tab; i++) {
557 poke = &prog->aux->poke_tab[i];
558 if (poke->aux && poke->aux != prog->aux)
559 continue;
560
561 WARN_ON_ONCE(READ_ONCE(poke->tailcall_target_stable));
562
563 if (poke->reason != BPF_POKE_REASON_TAIL_CALL)
564 continue;
565
566 array = container_of(poke->tail_call.map, struct bpf_array, map);
567 mutex_lock(&array->aux->poke_mutex);
568 target = array->ptrs[poke->tail_call.key];
569 if (target) {
570 /* Plain memcpy is used when image is not live yet
571 * and still not locked as read-only. Once poke
572 * location is active (poke->tailcall_target_stable),
573 * any parallel bpf_arch_text_poke() might occur
574 * still on the read-write image until we finally
575 * locked it as read-only. Both modifications on
576 * the given image are under text_mutex to avoid
577 * interference.
578 */
579 ret = __bpf_arch_text_poke(poke->tailcall_target,
580 BPF_MOD_JUMP, NULL,
581 (u8 *)target->bpf_func +
582 poke->adj_off, false);
583 BUG_ON(ret < 0);
584 ret = __bpf_arch_text_poke(poke->tailcall_bypass,
585 BPF_MOD_JUMP,
586 (u8 *)poke->tailcall_target +
587 X86_PATCH_SIZE, NULL, false);
588 BUG_ON(ret < 0);
589 }
590 WRITE_ONCE(poke->tailcall_target_stable, true);
591 mutex_unlock(&array->aux->poke_mutex);
592 }
593 }
594
emit_mov_imm32(u8 ** pprog,bool sign_propagate,u32 dst_reg,const u32 imm32)595 static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
596 u32 dst_reg, const u32 imm32)
597 {
598 u8 *prog = *pprog;
599 u8 b1, b2, b3;
600 int cnt = 0;
601
602 /*
603 * Optimization: if imm32 is positive, use 'mov %eax, imm32'
604 * (which zero-extends imm32) to save 2 bytes.
605 */
606 if (sign_propagate && (s32)imm32 < 0) {
607 /* 'mov %rax, imm32' sign extends imm32 */
608 b1 = add_1mod(0x48, dst_reg);
609 b2 = 0xC7;
610 b3 = 0xC0;
611 EMIT3_off32(b1, b2, add_1reg(b3, dst_reg), imm32);
612 goto done;
613 }
614
615 /*
616 * Optimization: if imm32 is zero, use 'xor %eax, %eax'
617 * to save 3 bytes.
618 */
619 if (imm32 == 0) {
620 if (is_ereg(dst_reg))
621 EMIT1(add_2mod(0x40, dst_reg, dst_reg));
622 b2 = 0x31; /* xor */
623 b3 = 0xC0;
624 EMIT2(b2, add_2reg(b3, dst_reg, dst_reg));
625 goto done;
626 }
627
628 /* mov %eax, imm32 */
629 if (is_ereg(dst_reg))
630 EMIT1(add_1mod(0x40, dst_reg));
631 EMIT1_off32(add_1reg(0xB8, dst_reg), imm32);
632 done:
633 *pprog = prog;
634 }
635
emit_mov_imm64(u8 ** pprog,u32 dst_reg,const u32 imm32_hi,const u32 imm32_lo)636 static void emit_mov_imm64(u8 **pprog, u32 dst_reg,
637 const u32 imm32_hi, const u32 imm32_lo)
638 {
639 u8 *prog = *pprog;
640 int cnt = 0;
641
642 if (is_uimm32(((u64)imm32_hi << 32) | (u32)imm32_lo)) {
643 /*
644 * For emitting plain u32, where sign bit must not be
645 * propagated LLVM tends to load imm64 over mov32
646 * directly, so save couple of bytes by just doing
647 * 'mov %eax, imm32' instead.
648 */
649 emit_mov_imm32(&prog, false, dst_reg, imm32_lo);
650 } else {
651 /* movabsq %rax, imm64 */
652 EMIT2(add_1mod(0x48, dst_reg), add_1reg(0xB8, dst_reg));
653 EMIT(imm32_lo, 4);
654 EMIT(imm32_hi, 4);
655 }
656
657 *pprog = prog;
658 }
659
emit_mov_reg(u8 ** pprog,bool is64,u32 dst_reg,u32 src_reg)660 static void emit_mov_reg(u8 **pprog, bool is64, u32 dst_reg, u32 src_reg)
661 {
662 u8 *prog = *pprog;
663 int cnt = 0;
664
665 if (is64) {
666 /* mov dst, src */
667 EMIT_mov(dst_reg, src_reg);
668 } else {
669 /* mov32 dst, src */
670 if (is_ereg(dst_reg) || is_ereg(src_reg))
671 EMIT1(add_2mod(0x40, dst_reg, src_reg));
672 EMIT2(0x89, add_2reg(0xC0, dst_reg, src_reg));
673 }
674
675 *pprog = prog;
676 }
677
678 /* LDX: dst_reg = *(u8*)(src_reg + off) */
emit_ldx(u8 ** pprog,u32 size,u32 dst_reg,u32 src_reg,int off)679 static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
680 {
681 u8 *prog = *pprog;
682 int cnt = 0;
683
684 switch (size) {
685 case BPF_B:
686 /* Emit 'movzx rax, byte ptr [rax + off]' */
687 EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB6);
688 break;
689 case BPF_H:
690 /* Emit 'movzx rax, word ptr [rax + off]' */
691 EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB7);
692 break;
693 case BPF_W:
694 /* Emit 'mov eax, dword ptr [rax+0x14]' */
695 if (is_ereg(dst_reg) || is_ereg(src_reg))
696 EMIT2(add_2mod(0x40, src_reg, dst_reg), 0x8B);
697 else
698 EMIT1(0x8B);
699 break;
700 case BPF_DW:
701 /* Emit 'mov rax, qword ptr [rax+0x14]' */
702 EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B);
703 break;
704 }
705 /*
706 * If insn->off == 0 we can save one extra byte, but
707 * special case of x86 R13 which always needs an offset
708 * is not worth the hassle
709 */
710 if (is_imm8(off))
711 EMIT2(add_2reg(0x40, src_reg, dst_reg), off);
712 else
713 EMIT1_off32(add_2reg(0x80, src_reg, dst_reg), off);
714 *pprog = prog;
715 }
716
717 /* STX: *(u8*)(dst_reg + off) = src_reg */
emit_stx(u8 ** pprog,u32 size,u32 dst_reg,u32 src_reg,int off)718 static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
719 {
720 u8 *prog = *pprog;
721 int cnt = 0;
722
723 switch (size) {
724 case BPF_B:
725 /* Emit 'mov byte ptr [rax + off], al' */
726 if (is_ereg(dst_reg) || is_ereg_8l(src_reg))
727 /* Add extra byte for eregs or SIL,DIL,BPL in src_reg */
728 EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88);
729 else
730 EMIT1(0x88);
731 break;
732 case BPF_H:
733 if (is_ereg(dst_reg) || is_ereg(src_reg))
734 EMIT3(0x66, add_2mod(0x40, dst_reg, src_reg), 0x89);
735 else
736 EMIT2(0x66, 0x89);
737 break;
738 case BPF_W:
739 if (is_ereg(dst_reg) || is_ereg(src_reg))
740 EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x89);
741 else
742 EMIT1(0x89);
743 break;
744 case BPF_DW:
745 EMIT2(add_2mod(0x48, dst_reg, src_reg), 0x89);
746 break;
747 }
748 if (is_imm8(off))
749 EMIT2(add_2reg(0x40, dst_reg, src_reg), off);
750 else
751 EMIT1_off32(add_2reg(0x80, dst_reg, src_reg), off);
752 *pprog = prog;
753 }
754
ex_handler_bpf(const struct exception_table_entry * x,struct pt_regs * regs,int trapnr,unsigned long error_code,unsigned long fault_addr)755 static bool ex_handler_bpf(const struct exception_table_entry *x,
756 struct pt_regs *regs, int trapnr,
757 unsigned long error_code, unsigned long fault_addr)
758 {
759 u32 reg = x->fixup >> 8;
760
761 /* jump over faulting load and clear dest register */
762 *(unsigned long *)((void *)regs + reg) = 0;
763 regs->ip += x->fixup & 0xff;
764 return true;
765 }
766
detect_reg_usage(struct bpf_insn * insn,int insn_cnt,bool * regs_used,bool * tail_call_seen)767 static void detect_reg_usage(struct bpf_insn *insn, int insn_cnt,
768 bool *regs_used, bool *tail_call_seen)
769 {
770 int i;
771
772 for (i = 1; i <= insn_cnt; i++, insn++) {
773 if (insn->code == (BPF_JMP | BPF_TAIL_CALL))
774 *tail_call_seen = true;
775 if (insn->dst_reg == BPF_REG_6 || insn->src_reg == BPF_REG_6)
776 regs_used[0] = true;
777 if (insn->dst_reg == BPF_REG_7 || insn->src_reg == BPF_REG_7)
778 regs_used[1] = true;
779 if (insn->dst_reg == BPF_REG_8 || insn->src_reg == BPF_REG_8)
780 regs_used[2] = true;
781 if (insn->dst_reg == BPF_REG_9 || insn->src_reg == BPF_REG_9)
782 regs_used[3] = true;
783 }
784 }
785
do_jit(struct bpf_prog * bpf_prog,int * addrs,u8 * image,int oldproglen,struct jit_context * ctx)786 static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
787 int oldproglen, struct jit_context *ctx)
788 {
789 bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
790 struct bpf_insn *insn = bpf_prog->insnsi;
791 bool callee_regs_used[4] = {};
792 int insn_cnt = bpf_prog->len;
793 bool tail_call_seen = false;
794 bool seen_exit = false;
795 u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
796 int i, cnt = 0, excnt = 0;
797 int proglen = 0;
798 u8 *prog = temp;
799
800 detect_reg_usage(insn, insn_cnt, callee_regs_used,
801 &tail_call_seen);
802
803 /* tail call's presence in current prog implies it is reachable */
804 tail_call_reachable |= tail_call_seen;
805
806 emit_prologue(&prog, bpf_prog->aux->stack_depth,
807 bpf_prog_was_classic(bpf_prog), tail_call_reachable,
808 bpf_prog->aux->func_idx != 0);
809 push_callee_regs(&prog, callee_regs_used);
810 addrs[0] = prog - temp;
811
812 for (i = 1; i <= insn_cnt; i++, insn++) {
813 const s32 imm32 = insn->imm;
814 u32 dst_reg = insn->dst_reg;
815 u32 src_reg = insn->src_reg;
816 u8 b2 = 0, b3 = 0;
817 s64 jmp_offset;
818 u8 jmp_cond;
819 int ilen;
820 u8 *func;
821
822 switch (insn->code) {
823 /* ALU */
824 case BPF_ALU | BPF_ADD | BPF_X:
825 case BPF_ALU | BPF_SUB | BPF_X:
826 case BPF_ALU | BPF_AND | BPF_X:
827 case BPF_ALU | BPF_OR | BPF_X:
828 case BPF_ALU | BPF_XOR | BPF_X:
829 case BPF_ALU64 | BPF_ADD | BPF_X:
830 case BPF_ALU64 | BPF_SUB | BPF_X:
831 case BPF_ALU64 | BPF_AND | BPF_X:
832 case BPF_ALU64 | BPF_OR | BPF_X:
833 case BPF_ALU64 | BPF_XOR | BPF_X:
834 switch (BPF_OP(insn->code)) {
835 case BPF_ADD: b2 = 0x01; break;
836 case BPF_SUB: b2 = 0x29; break;
837 case BPF_AND: b2 = 0x21; break;
838 case BPF_OR: b2 = 0x09; break;
839 case BPF_XOR: b2 = 0x31; break;
840 }
841 if (BPF_CLASS(insn->code) == BPF_ALU64)
842 EMIT1(add_2mod(0x48, dst_reg, src_reg));
843 else if (is_ereg(dst_reg) || is_ereg(src_reg))
844 EMIT1(add_2mod(0x40, dst_reg, src_reg));
845 EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
846 break;
847
848 case BPF_ALU64 | BPF_MOV | BPF_X:
849 case BPF_ALU | BPF_MOV | BPF_X:
850 emit_mov_reg(&prog,
851 BPF_CLASS(insn->code) == BPF_ALU64,
852 dst_reg, src_reg);
853 break;
854
855 /* neg dst */
856 case BPF_ALU | BPF_NEG:
857 case BPF_ALU64 | BPF_NEG:
858 if (BPF_CLASS(insn->code) == BPF_ALU64)
859 EMIT1(add_1mod(0x48, dst_reg));
860 else if (is_ereg(dst_reg))
861 EMIT1(add_1mod(0x40, dst_reg));
862 EMIT2(0xF7, add_1reg(0xD8, dst_reg));
863 break;
864
865 case BPF_ALU | BPF_ADD | BPF_K:
866 case BPF_ALU | BPF_SUB | BPF_K:
867 case BPF_ALU | BPF_AND | BPF_K:
868 case BPF_ALU | BPF_OR | BPF_K:
869 case BPF_ALU | BPF_XOR | BPF_K:
870 case BPF_ALU64 | BPF_ADD | BPF_K:
871 case BPF_ALU64 | BPF_SUB | BPF_K:
872 case BPF_ALU64 | BPF_AND | BPF_K:
873 case BPF_ALU64 | BPF_OR | BPF_K:
874 case BPF_ALU64 | BPF_XOR | BPF_K:
875 if (BPF_CLASS(insn->code) == BPF_ALU64)
876 EMIT1(add_1mod(0x48, dst_reg));
877 else if (is_ereg(dst_reg))
878 EMIT1(add_1mod(0x40, dst_reg));
879
880 /*
881 * b3 holds 'normal' opcode, b2 short form only valid
882 * in case dst is eax/rax.
883 */
884 switch (BPF_OP(insn->code)) {
885 case BPF_ADD:
886 b3 = 0xC0;
887 b2 = 0x05;
888 break;
889 case BPF_SUB:
890 b3 = 0xE8;
891 b2 = 0x2D;
892 break;
893 case BPF_AND:
894 b3 = 0xE0;
895 b2 = 0x25;
896 break;
897 case BPF_OR:
898 b3 = 0xC8;
899 b2 = 0x0D;
900 break;
901 case BPF_XOR:
902 b3 = 0xF0;
903 b2 = 0x35;
904 break;
905 }
906
907 if (is_imm8(imm32))
908 EMIT3(0x83, add_1reg(b3, dst_reg), imm32);
909 else if (is_axreg(dst_reg))
910 EMIT1_off32(b2, imm32);
911 else
912 EMIT2_off32(0x81, add_1reg(b3, dst_reg), imm32);
913 break;
914
915 case BPF_ALU64 | BPF_MOV | BPF_K:
916 case BPF_ALU | BPF_MOV | BPF_K:
917 emit_mov_imm32(&prog, BPF_CLASS(insn->code) == BPF_ALU64,
918 dst_reg, imm32);
919 break;
920
921 case BPF_LD | BPF_IMM | BPF_DW:
922 emit_mov_imm64(&prog, dst_reg, insn[1].imm, insn[0].imm);
923 insn++;
924 i++;
925 break;
926
927 /* dst %= src, dst /= src, dst %= imm32, dst /= imm32 */
928 case BPF_ALU | BPF_MOD | BPF_X:
929 case BPF_ALU | BPF_DIV | BPF_X:
930 case BPF_ALU | BPF_MOD | BPF_K:
931 case BPF_ALU | BPF_DIV | BPF_K:
932 case BPF_ALU64 | BPF_MOD | BPF_X:
933 case BPF_ALU64 | BPF_DIV | BPF_X:
934 case BPF_ALU64 | BPF_MOD | BPF_K:
935 case BPF_ALU64 | BPF_DIV | BPF_K:
936 EMIT1(0x50); /* push rax */
937 EMIT1(0x52); /* push rdx */
938
939 if (BPF_SRC(insn->code) == BPF_X)
940 /* mov r11, src_reg */
941 EMIT_mov(AUX_REG, src_reg);
942 else
943 /* mov r11, imm32 */
944 EMIT3_off32(0x49, 0xC7, 0xC3, imm32);
945
946 /* mov rax, dst_reg */
947 EMIT_mov(BPF_REG_0, dst_reg);
948
949 /*
950 * xor edx, edx
951 * equivalent to 'xor rdx, rdx', but one byte less
952 */
953 EMIT2(0x31, 0xd2);
954
955 if (BPF_CLASS(insn->code) == BPF_ALU64)
956 /* div r11 */
957 EMIT3(0x49, 0xF7, 0xF3);
958 else
959 /* div r11d */
960 EMIT3(0x41, 0xF7, 0xF3);
961
962 if (BPF_OP(insn->code) == BPF_MOD)
963 /* mov r11, rdx */
964 EMIT3(0x49, 0x89, 0xD3);
965 else
966 /* mov r11, rax */
967 EMIT3(0x49, 0x89, 0xC3);
968
969 EMIT1(0x5A); /* pop rdx */
970 EMIT1(0x58); /* pop rax */
971
972 /* mov dst_reg, r11 */
973 EMIT_mov(dst_reg, AUX_REG);
974 break;
975
976 case BPF_ALU | BPF_MUL | BPF_K:
977 case BPF_ALU | BPF_MUL | BPF_X:
978 case BPF_ALU64 | BPF_MUL | BPF_K:
979 case BPF_ALU64 | BPF_MUL | BPF_X:
980 {
981 bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
982
983 if (dst_reg != BPF_REG_0)
984 EMIT1(0x50); /* push rax */
985 if (dst_reg != BPF_REG_3)
986 EMIT1(0x52); /* push rdx */
987
988 /* mov r11, dst_reg */
989 EMIT_mov(AUX_REG, dst_reg);
990
991 if (BPF_SRC(insn->code) == BPF_X)
992 emit_mov_reg(&prog, is64, BPF_REG_0, src_reg);
993 else
994 emit_mov_imm32(&prog, is64, BPF_REG_0, imm32);
995
996 if (is64)
997 EMIT1(add_1mod(0x48, AUX_REG));
998 else if (is_ereg(AUX_REG))
999 EMIT1(add_1mod(0x40, AUX_REG));
1000 /* mul(q) r11 */
1001 EMIT2(0xF7, add_1reg(0xE0, AUX_REG));
1002
1003 if (dst_reg != BPF_REG_3)
1004 EMIT1(0x5A); /* pop rdx */
1005 if (dst_reg != BPF_REG_0) {
1006 /* mov dst_reg, rax */
1007 EMIT_mov(dst_reg, BPF_REG_0);
1008 EMIT1(0x58); /* pop rax */
1009 }
1010 break;
1011 }
1012 /* Shifts */
1013 case BPF_ALU | BPF_LSH | BPF_K:
1014 case BPF_ALU | BPF_RSH | BPF_K:
1015 case BPF_ALU | BPF_ARSH | BPF_K:
1016 case BPF_ALU64 | BPF_LSH | BPF_K:
1017 case BPF_ALU64 | BPF_RSH | BPF_K:
1018 case BPF_ALU64 | BPF_ARSH | BPF_K:
1019 if (BPF_CLASS(insn->code) == BPF_ALU64)
1020 EMIT1(add_1mod(0x48, dst_reg));
1021 else if (is_ereg(dst_reg))
1022 EMIT1(add_1mod(0x40, dst_reg));
1023
1024 switch (BPF_OP(insn->code)) {
1025 case BPF_LSH: b3 = 0xE0; break;
1026 case BPF_RSH: b3 = 0xE8; break;
1027 case BPF_ARSH: b3 = 0xF8; break;
1028 }
1029
1030 if (imm32 == 1)
1031 EMIT2(0xD1, add_1reg(b3, dst_reg));
1032 else
1033 EMIT3(0xC1, add_1reg(b3, dst_reg), imm32);
1034 break;
1035
1036 case BPF_ALU | BPF_LSH | BPF_X:
1037 case BPF_ALU | BPF_RSH | BPF_X:
1038 case BPF_ALU | BPF_ARSH | BPF_X:
1039 case BPF_ALU64 | BPF_LSH | BPF_X:
1040 case BPF_ALU64 | BPF_RSH | BPF_X:
1041 case BPF_ALU64 | BPF_ARSH | BPF_X:
1042
1043 /* Check for bad case when dst_reg == rcx */
1044 if (dst_reg == BPF_REG_4) {
1045 /* mov r11, dst_reg */
1046 EMIT_mov(AUX_REG, dst_reg);
1047 dst_reg = AUX_REG;
1048 }
1049
1050 if (src_reg != BPF_REG_4) { /* common case */
1051 EMIT1(0x51); /* push rcx */
1052
1053 /* mov rcx, src_reg */
1054 EMIT_mov(BPF_REG_4, src_reg);
1055 }
1056
1057 /* shl %rax, %cl | shr %rax, %cl | sar %rax, %cl */
1058 if (BPF_CLASS(insn->code) == BPF_ALU64)
1059 EMIT1(add_1mod(0x48, dst_reg));
1060 else if (is_ereg(dst_reg))
1061 EMIT1(add_1mod(0x40, dst_reg));
1062
1063 switch (BPF_OP(insn->code)) {
1064 case BPF_LSH: b3 = 0xE0; break;
1065 case BPF_RSH: b3 = 0xE8; break;
1066 case BPF_ARSH: b3 = 0xF8; break;
1067 }
1068 EMIT2(0xD3, add_1reg(b3, dst_reg));
1069
1070 if (src_reg != BPF_REG_4)
1071 EMIT1(0x59); /* pop rcx */
1072
1073 if (insn->dst_reg == BPF_REG_4)
1074 /* mov dst_reg, r11 */
1075 EMIT_mov(insn->dst_reg, AUX_REG);
1076 break;
1077
1078 case BPF_ALU | BPF_END | BPF_FROM_BE:
1079 switch (imm32) {
1080 case 16:
1081 /* Emit 'ror %ax, 8' to swap lower 2 bytes */
1082 EMIT1(0x66);
1083 if (is_ereg(dst_reg))
1084 EMIT1(0x41);
1085 EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8);
1086
1087 /* Emit 'movzwl eax, ax' */
1088 if (is_ereg(dst_reg))
1089 EMIT3(0x45, 0x0F, 0xB7);
1090 else
1091 EMIT2(0x0F, 0xB7);
1092 EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
1093 break;
1094 case 32:
1095 /* Emit 'bswap eax' to swap lower 4 bytes */
1096 if (is_ereg(dst_reg))
1097 EMIT2(0x41, 0x0F);
1098 else
1099 EMIT1(0x0F);
1100 EMIT1(add_1reg(0xC8, dst_reg));
1101 break;
1102 case 64:
1103 /* Emit 'bswap rax' to swap 8 bytes */
1104 EMIT3(add_1mod(0x48, dst_reg), 0x0F,
1105 add_1reg(0xC8, dst_reg));
1106 break;
1107 }
1108 break;
1109
1110 case BPF_ALU | BPF_END | BPF_FROM_LE:
1111 switch (imm32) {
1112 case 16:
1113 /*
1114 * Emit 'movzwl eax, ax' to zero extend 16-bit
1115 * into 64 bit
1116 */
1117 if (is_ereg(dst_reg))
1118 EMIT3(0x45, 0x0F, 0xB7);
1119 else
1120 EMIT2(0x0F, 0xB7);
1121 EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
1122 break;
1123 case 32:
1124 /* Emit 'mov eax, eax' to clear upper 32-bits */
1125 if (is_ereg(dst_reg))
1126 EMIT1(0x45);
1127 EMIT2(0x89, add_2reg(0xC0, dst_reg, dst_reg));
1128 break;
1129 case 64:
1130 /* nop */
1131 break;
1132 }
1133 break;
1134
1135 /* speculation barrier */
1136 case BPF_ST | BPF_NOSPEC:
1137 if (boot_cpu_has(X86_FEATURE_XMM2))
1138 EMIT_LFENCE();
1139 break;
1140
1141 /* ST: *(u8*)(dst_reg + off) = imm */
1142 case BPF_ST | BPF_MEM | BPF_B:
1143 if (is_ereg(dst_reg))
1144 EMIT2(0x41, 0xC6);
1145 else
1146 EMIT1(0xC6);
1147 goto st;
1148 case BPF_ST | BPF_MEM | BPF_H:
1149 if (is_ereg(dst_reg))
1150 EMIT3(0x66, 0x41, 0xC7);
1151 else
1152 EMIT2(0x66, 0xC7);
1153 goto st;
1154 case BPF_ST | BPF_MEM | BPF_W:
1155 if (is_ereg(dst_reg))
1156 EMIT2(0x41, 0xC7);
1157 else
1158 EMIT1(0xC7);
1159 goto st;
1160 case BPF_ST | BPF_MEM | BPF_DW:
1161 EMIT2(add_1mod(0x48, dst_reg), 0xC7);
1162
1163 st: if (is_imm8(insn->off))
1164 EMIT2(add_1reg(0x40, dst_reg), insn->off);
1165 else
1166 EMIT1_off32(add_1reg(0x80, dst_reg), insn->off);
1167
1168 EMIT(imm32, bpf_size_to_x86_bytes(BPF_SIZE(insn->code)));
1169 break;
1170
1171 /* STX: *(u8*)(dst_reg + off) = src_reg */
1172 case BPF_STX | BPF_MEM | BPF_B:
1173 case BPF_STX | BPF_MEM | BPF_H:
1174 case BPF_STX | BPF_MEM | BPF_W:
1175 case BPF_STX | BPF_MEM | BPF_DW:
1176 emit_stx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn->off);
1177 break;
1178
1179 /* LDX: dst_reg = *(u8*)(src_reg + off) */
1180 case BPF_LDX | BPF_MEM | BPF_B:
1181 case BPF_LDX | BPF_PROBE_MEM | BPF_B:
1182 case BPF_LDX | BPF_MEM | BPF_H:
1183 case BPF_LDX | BPF_PROBE_MEM | BPF_H:
1184 case BPF_LDX | BPF_MEM | BPF_W:
1185 case BPF_LDX | BPF_PROBE_MEM | BPF_W:
1186 case BPF_LDX | BPF_MEM | BPF_DW:
1187 case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
1188 emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn->off);
1189 if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
1190 struct exception_table_entry *ex;
1191 u8 *_insn = image + proglen;
1192 s64 delta;
1193
1194 if (!bpf_prog->aux->extable)
1195 break;
1196
1197 if (excnt >= bpf_prog->aux->num_exentries) {
1198 pr_err("ex gen bug\n");
1199 return -EFAULT;
1200 }
1201 ex = &bpf_prog->aux->extable[excnt++];
1202
1203 delta = _insn - (u8 *)&ex->insn;
1204 if (!is_simm32(delta)) {
1205 pr_err("extable->insn doesn't fit into 32-bit\n");
1206 return -EFAULT;
1207 }
1208 ex->insn = delta;
1209
1210 delta = (u8 *)ex_handler_bpf - (u8 *)&ex->handler;
1211 if (!is_simm32(delta)) {
1212 pr_err("extable->handler doesn't fit into 32-bit\n");
1213 return -EFAULT;
1214 }
1215 ex->handler = delta;
1216
1217 if (dst_reg > BPF_REG_9) {
1218 pr_err("verifier error\n");
1219 return -EFAULT;
1220 }
1221 /*
1222 * Compute size of x86 insn and its target dest x86 register.
1223 * ex_handler_bpf() will use lower 8 bits to adjust
1224 * pt_regs->ip to jump over this x86 instruction
1225 * and upper bits to figure out which pt_regs to zero out.
1226 * End result: x86 insn "mov rbx, qword ptr [rax+0x14]"
1227 * of 4 bytes will be ignored and rbx will be zero inited.
1228 */
1229 ex->fixup = (prog - temp) | (reg2pt_regs[dst_reg] << 8);
1230 }
1231 break;
1232
1233 /* STX XADD: lock *(u32*)(dst_reg + off) += src_reg */
1234 case BPF_STX | BPF_XADD | BPF_W:
1235 /* Emit 'lock add dword ptr [rax + off], eax' */
1236 if (is_ereg(dst_reg) || is_ereg(src_reg))
1237 EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01);
1238 else
1239 EMIT2(0xF0, 0x01);
1240 goto xadd;
1241 case BPF_STX | BPF_XADD | BPF_DW:
1242 EMIT3(0xF0, add_2mod(0x48, dst_reg, src_reg), 0x01);
1243 xadd: if (is_imm8(insn->off))
1244 EMIT2(add_2reg(0x40, dst_reg, src_reg), insn->off);
1245 else
1246 EMIT1_off32(add_2reg(0x80, dst_reg, src_reg),
1247 insn->off);
1248 break;
1249
1250 /* call */
1251 case BPF_JMP | BPF_CALL:
1252 func = (u8 *) __bpf_call_base + imm32;
1253 if (tail_call_reachable) {
1254 EMIT3_off32(0x48, 0x8B, 0x85,
1255 -(bpf_prog->aux->stack_depth + 8));
1256 if (!imm32 || emit_call(&prog, func, image + addrs[i - 1] + 7))
1257 return -EINVAL;
1258 } else {
1259 if (!imm32 || emit_call(&prog, func, image + addrs[i - 1]))
1260 return -EINVAL;
1261 }
1262 break;
1263
1264 case BPF_JMP | BPF_TAIL_CALL:
1265 if (imm32)
1266 emit_bpf_tail_call_direct(&bpf_prog->aux->poke_tab[imm32 - 1],
1267 &prog, image + addrs[i - 1],
1268 callee_regs_used,
1269 bpf_prog->aux->stack_depth,
1270 ctx);
1271 else
1272 emit_bpf_tail_call_indirect(&prog,
1273 callee_regs_used,
1274 bpf_prog->aux->stack_depth,
1275 image + addrs[i - 1],
1276 ctx);
1277 break;
1278
1279 /* cond jump */
1280 case BPF_JMP | BPF_JEQ | BPF_X:
1281 case BPF_JMP | BPF_JNE | BPF_X:
1282 case BPF_JMP | BPF_JGT | BPF_X:
1283 case BPF_JMP | BPF_JLT | BPF_X:
1284 case BPF_JMP | BPF_JGE | BPF_X:
1285 case BPF_JMP | BPF_JLE | BPF_X:
1286 case BPF_JMP | BPF_JSGT | BPF_X:
1287 case BPF_JMP | BPF_JSLT | BPF_X:
1288 case BPF_JMP | BPF_JSGE | BPF_X:
1289 case BPF_JMP | BPF_JSLE | BPF_X:
1290 case BPF_JMP32 | BPF_JEQ | BPF_X:
1291 case BPF_JMP32 | BPF_JNE | BPF_X:
1292 case BPF_JMP32 | BPF_JGT | BPF_X:
1293 case BPF_JMP32 | BPF_JLT | BPF_X:
1294 case BPF_JMP32 | BPF_JGE | BPF_X:
1295 case BPF_JMP32 | BPF_JLE | BPF_X:
1296 case BPF_JMP32 | BPF_JSGT | BPF_X:
1297 case BPF_JMP32 | BPF_JSLT | BPF_X:
1298 case BPF_JMP32 | BPF_JSGE | BPF_X:
1299 case BPF_JMP32 | BPF_JSLE | BPF_X:
1300 /* cmp dst_reg, src_reg */
1301 if (BPF_CLASS(insn->code) == BPF_JMP)
1302 EMIT1(add_2mod(0x48, dst_reg, src_reg));
1303 else if (is_ereg(dst_reg) || is_ereg(src_reg))
1304 EMIT1(add_2mod(0x40, dst_reg, src_reg));
1305 EMIT2(0x39, add_2reg(0xC0, dst_reg, src_reg));
1306 goto emit_cond_jmp;
1307
1308 case BPF_JMP | BPF_JSET | BPF_X:
1309 case BPF_JMP32 | BPF_JSET | BPF_X:
1310 /* test dst_reg, src_reg */
1311 if (BPF_CLASS(insn->code) == BPF_JMP)
1312 EMIT1(add_2mod(0x48, dst_reg, src_reg));
1313 else if (is_ereg(dst_reg) || is_ereg(src_reg))
1314 EMIT1(add_2mod(0x40, dst_reg, src_reg));
1315 EMIT2(0x85, add_2reg(0xC0, dst_reg, src_reg));
1316 goto emit_cond_jmp;
1317
1318 case BPF_JMP | BPF_JSET | BPF_K:
1319 case BPF_JMP32 | BPF_JSET | BPF_K:
1320 /* test dst_reg, imm32 */
1321 if (BPF_CLASS(insn->code) == BPF_JMP)
1322 EMIT1(add_1mod(0x48, dst_reg));
1323 else if (is_ereg(dst_reg))
1324 EMIT1(add_1mod(0x40, dst_reg));
1325 EMIT2_off32(0xF7, add_1reg(0xC0, dst_reg), imm32);
1326 goto emit_cond_jmp;
1327
1328 case BPF_JMP | BPF_JEQ | BPF_K:
1329 case BPF_JMP | BPF_JNE | BPF_K:
1330 case BPF_JMP | BPF_JGT | BPF_K:
1331 case BPF_JMP | BPF_JLT | BPF_K:
1332 case BPF_JMP | BPF_JGE | BPF_K:
1333 case BPF_JMP | BPF_JLE | BPF_K:
1334 case BPF_JMP | BPF_JSGT | BPF_K:
1335 case BPF_JMP | BPF_JSLT | BPF_K:
1336 case BPF_JMP | BPF_JSGE | BPF_K:
1337 case BPF_JMP | BPF_JSLE | BPF_K:
1338 case BPF_JMP32 | BPF_JEQ | BPF_K:
1339 case BPF_JMP32 | BPF_JNE | BPF_K:
1340 case BPF_JMP32 | BPF_JGT | BPF_K:
1341 case BPF_JMP32 | BPF_JLT | BPF_K:
1342 case BPF_JMP32 | BPF_JGE | BPF_K:
1343 case BPF_JMP32 | BPF_JLE | BPF_K:
1344 case BPF_JMP32 | BPF_JSGT | BPF_K:
1345 case BPF_JMP32 | BPF_JSLT | BPF_K:
1346 case BPF_JMP32 | BPF_JSGE | BPF_K:
1347 case BPF_JMP32 | BPF_JSLE | BPF_K:
1348 /* test dst_reg, dst_reg to save one extra byte */
1349 if (imm32 == 0) {
1350 if (BPF_CLASS(insn->code) == BPF_JMP)
1351 EMIT1(add_2mod(0x48, dst_reg, dst_reg));
1352 else if (is_ereg(dst_reg))
1353 EMIT1(add_2mod(0x40, dst_reg, dst_reg));
1354 EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));
1355 goto emit_cond_jmp;
1356 }
1357
1358 /* cmp dst_reg, imm8/32 */
1359 if (BPF_CLASS(insn->code) == BPF_JMP)
1360 EMIT1(add_1mod(0x48, dst_reg));
1361 else if (is_ereg(dst_reg))
1362 EMIT1(add_1mod(0x40, dst_reg));
1363
1364 if (is_imm8(imm32))
1365 EMIT3(0x83, add_1reg(0xF8, dst_reg), imm32);
1366 else
1367 EMIT2_off32(0x81, add_1reg(0xF8, dst_reg), imm32);
1368
1369 emit_cond_jmp: /* Convert BPF opcode to x86 */
1370 switch (BPF_OP(insn->code)) {
1371 case BPF_JEQ:
1372 jmp_cond = X86_JE;
1373 break;
1374 case BPF_JSET:
1375 case BPF_JNE:
1376 jmp_cond = X86_JNE;
1377 break;
1378 case BPF_JGT:
1379 /* GT is unsigned '>', JA in x86 */
1380 jmp_cond = X86_JA;
1381 break;
1382 case BPF_JLT:
1383 /* LT is unsigned '<', JB in x86 */
1384 jmp_cond = X86_JB;
1385 break;
1386 case BPF_JGE:
1387 /* GE is unsigned '>=', JAE in x86 */
1388 jmp_cond = X86_JAE;
1389 break;
1390 case BPF_JLE:
1391 /* LE is unsigned '<=', JBE in x86 */
1392 jmp_cond = X86_JBE;
1393 break;
1394 case BPF_JSGT:
1395 /* Signed '>', GT in x86 */
1396 jmp_cond = X86_JG;
1397 break;
1398 case BPF_JSLT:
1399 /* Signed '<', LT in x86 */
1400 jmp_cond = X86_JL;
1401 break;
1402 case BPF_JSGE:
1403 /* Signed '>=', GE in x86 */
1404 jmp_cond = X86_JGE;
1405 break;
1406 case BPF_JSLE:
1407 /* Signed '<=', LE in x86 */
1408 jmp_cond = X86_JLE;
1409 break;
1410 default: /* to silence GCC warning */
1411 return -EFAULT;
1412 }
1413 jmp_offset = addrs[i + insn->off] - addrs[i];
1414 if (is_imm8(jmp_offset)) {
1415 EMIT2(jmp_cond, jmp_offset);
1416 } else if (is_simm32(jmp_offset)) {
1417 EMIT2_off32(0x0F, jmp_cond + 0x10, jmp_offset);
1418 } else {
1419 pr_err("cond_jmp gen bug %llx\n", jmp_offset);
1420 return -EFAULT;
1421 }
1422
1423 break;
1424
1425 case BPF_JMP | BPF_JA:
1426 if (insn->off == -1)
1427 /* -1 jmp instructions will always jump
1428 * backwards two bytes. Explicitly handling
1429 * this case avoids wasting too many passes
1430 * when there are long sequences of replaced
1431 * dead code.
1432 */
1433 jmp_offset = -2;
1434 else
1435 jmp_offset = addrs[i + insn->off] - addrs[i];
1436
1437 if (!jmp_offset)
1438 /* Optimize out nop jumps */
1439 break;
1440 emit_jmp:
1441 if (is_imm8(jmp_offset)) {
1442 EMIT2(0xEB, jmp_offset);
1443 } else if (is_simm32(jmp_offset)) {
1444 EMIT1_off32(0xE9, jmp_offset);
1445 } else {
1446 pr_err("jmp gen bug %llx\n", jmp_offset);
1447 return -EFAULT;
1448 }
1449 break;
1450
1451 case BPF_JMP | BPF_EXIT:
1452 if (seen_exit) {
1453 jmp_offset = ctx->cleanup_addr - addrs[i];
1454 goto emit_jmp;
1455 }
1456 seen_exit = true;
1457 /* Update cleanup_addr */
1458 ctx->cleanup_addr = proglen;
1459 pop_callee_regs(&prog, callee_regs_used);
1460 EMIT1(0xC9); /* leave */
1461 emit_return(&prog, image + addrs[i - 1] + (prog - temp));
1462 break;
1463
1464 default:
1465 /*
1466 * By design x86-64 JIT should support all BPF instructions.
1467 * This error will be seen if new instruction was added
1468 * to the interpreter, but not to the JIT, or if there is
1469 * junk in bpf_prog.
1470 */
1471 pr_err("bpf_jit: unknown opcode %02x\n", insn->code);
1472 return -EINVAL;
1473 }
1474
1475 ilen = prog - temp;
1476 if (ilen > BPF_MAX_INSN_SIZE) {
1477 pr_err("bpf_jit: fatal insn size error\n");
1478 return -EFAULT;
1479 }
1480
1481 if (image) {
1482 /*
1483 * When populating the image, assert that:
1484 *
1485 * i) We do not write beyond the allocated space, and
1486 * ii) addrs[i] did not change from the prior run, in order
1487 * to validate assumptions made for computing branch
1488 * displacements.
1489 */
1490 if (unlikely(proglen + ilen > oldproglen ||
1491 proglen + ilen != addrs[i])) {
1492 pr_err("bpf_jit: fatal error\n");
1493 return -EFAULT;
1494 }
1495 memcpy(image + proglen, temp, ilen);
1496 }
1497 proglen += ilen;
1498 addrs[i] = proglen;
1499 prog = temp;
1500 }
1501
1502 if (image && excnt != bpf_prog->aux->num_exentries) {
1503 pr_err("extable is not populated\n");
1504 return -EFAULT;
1505 }
1506 return proglen;
1507 }
1508
save_regs(const struct btf_func_model * m,u8 ** prog,int nr_args,int stack_size)1509 static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
1510 int stack_size)
1511 {
1512 int i;
1513 /* Store function arguments to stack.
1514 * For a function that accepts two pointers the sequence will be:
1515 * mov QWORD PTR [rbp-0x10],rdi
1516 * mov QWORD PTR [rbp-0x8],rsi
1517 */
1518 for (i = 0; i < min(nr_args, 6); i++)
1519 emit_stx(prog, bytes_to_bpf_size(m->arg_size[i]),
1520 BPF_REG_FP,
1521 i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
1522 -(stack_size - i * 8));
1523 }
1524
restore_regs(const struct btf_func_model * m,u8 ** prog,int nr_args,int stack_size)1525 static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
1526 int stack_size)
1527 {
1528 int i;
1529
1530 /* Restore function arguments from stack.
1531 * For a function that accepts two pointers the sequence will be:
1532 * EMIT4(0x48, 0x8B, 0x7D, 0xF0); mov rdi,QWORD PTR [rbp-0x10]
1533 * EMIT4(0x48, 0x8B, 0x75, 0xF8); mov rsi,QWORD PTR [rbp-0x8]
1534 */
1535 for (i = 0; i < min(nr_args, 6); i++)
1536 emit_ldx(prog, bytes_to_bpf_size(m->arg_size[i]),
1537 i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
1538 BPF_REG_FP,
1539 -(stack_size - i * 8));
1540 }
1541
invoke_bpf_prog(const struct btf_func_model * m,u8 ** pprog,struct bpf_prog * p,int stack_size,bool save_ret)1542 static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
1543 struct bpf_prog *p, int stack_size, bool save_ret)
1544 {
1545 u8 *prog = *pprog;
1546 int cnt = 0;
1547
1548 if (p->aux->sleepable) {
1549 if (emit_call(&prog, __bpf_prog_enter_sleepable, prog))
1550 return -EINVAL;
1551 } else {
1552 if (emit_call(&prog, __bpf_prog_enter, prog))
1553 return -EINVAL;
1554 /* remember prog start time returned by __bpf_prog_enter */
1555 emit_mov_reg(&prog, true, BPF_REG_6, BPF_REG_0);
1556 }
1557
1558 /* arg1: lea rdi, [rbp - stack_size] */
1559 EMIT4(0x48, 0x8D, 0x7D, -stack_size);
1560 /* arg2: progs[i]->insnsi for interpreter */
1561 if (!p->jited)
1562 emit_mov_imm64(&prog, BPF_REG_2,
1563 (long) p->insnsi >> 32,
1564 (u32) (long) p->insnsi);
1565 /* call JITed bpf program or interpreter */
1566 if (emit_call(&prog, p->bpf_func, prog))
1567 return -EINVAL;
1568
1569 /*
1570 * BPF_TRAMP_MODIFY_RETURN trampolines can modify the return
1571 * of the previous call which is then passed on the stack to
1572 * the next BPF program.
1573 *
1574 * BPF_TRAMP_FENTRY trampoline may need to return the return
1575 * value of BPF_PROG_TYPE_STRUCT_OPS prog.
1576 */
1577 if (save_ret)
1578 emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
1579
1580 if (p->aux->sleepable) {
1581 if (emit_call(&prog, __bpf_prog_exit_sleepable, prog))
1582 return -EINVAL;
1583 } else {
1584 /* arg1: mov rdi, progs[i] */
1585 emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32,
1586 (u32) (long) p);
1587 /* arg2: mov rsi, rbx <- start time in nsec */
1588 emit_mov_reg(&prog, true, BPF_REG_2, BPF_REG_6);
1589 if (emit_call(&prog, __bpf_prog_exit, prog))
1590 return -EINVAL;
1591 }
1592
1593 *pprog = prog;
1594 return 0;
1595 }
1596
emit_nops(u8 ** pprog,unsigned int len)1597 static void emit_nops(u8 **pprog, unsigned int len)
1598 {
1599 unsigned int i, noplen;
1600 u8 *prog = *pprog;
1601 int cnt = 0;
1602
1603 while (len > 0) {
1604 noplen = len;
1605
1606 if (noplen > ASM_NOP_MAX)
1607 noplen = ASM_NOP_MAX;
1608
1609 for (i = 0; i < noplen; i++)
1610 EMIT1(ideal_nops[noplen][i]);
1611 len -= noplen;
1612 }
1613
1614 *pprog = prog;
1615 }
1616
emit_align(u8 ** pprog,u32 align)1617 static void emit_align(u8 **pprog, u32 align)
1618 {
1619 u8 *target, *prog = *pprog;
1620
1621 target = PTR_ALIGN(prog, align);
1622 if (target != prog)
1623 emit_nops(&prog, target - prog);
1624
1625 *pprog = prog;
1626 }
1627
emit_cond_near_jump(u8 ** pprog,void * func,void * ip,u8 jmp_cond)1628 static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond)
1629 {
1630 u8 *prog = *pprog;
1631 int cnt = 0;
1632 s64 offset;
1633
1634 offset = func - (ip + 2 + 4);
1635 if (!is_simm32(offset)) {
1636 pr_err("Target %p is out of range\n", func);
1637 return -EINVAL;
1638 }
1639 EMIT2_off32(0x0F, jmp_cond + 0x10, offset);
1640 *pprog = prog;
1641 return 0;
1642 }
1643
invoke_bpf(const struct btf_func_model * m,u8 ** pprog,struct bpf_tramp_progs * tp,int stack_size,bool save_ret)1644 static int invoke_bpf(const struct btf_func_model *m, u8 **pprog,
1645 struct bpf_tramp_progs *tp, int stack_size,
1646 bool save_ret)
1647 {
1648 int i;
1649 u8 *prog = *pprog;
1650
1651 for (i = 0; i < tp->nr_progs; i++) {
1652 if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size,
1653 save_ret))
1654 return -EINVAL;
1655 }
1656 *pprog = prog;
1657 return 0;
1658 }
1659
invoke_bpf_mod_ret(const struct btf_func_model * m,u8 ** pprog,struct bpf_tramp_progs * tp,int stack_size,u8 ** branches)1660 static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog,
1661 struct bpf_tramp_progs *tp, int stack_size,
1662 u8 **branches)
1663 {
1664 u8 *prog = *pprog;
1665 int i, cnt = 0;
1666
1667 /* The first fmod_ret program will receive a garbage return value.
1668 * Set this to 0 to avoid confusing the program.
1669 */
1670 emit_mov_imm32(&prog, false, BPF_REG_0, 0);
1671 emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
1672 for (i = 0; i < tp->nr_progs; i++) {
1673 if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size, true))
1674 return -EINVAL;
1675
1676 /* mod_ret prog stored return value into [rbp - 8]. Emit:
1677 * if (*(u64 *)(rbp - 8) != 0)
1678 * goto do_fexit;
1679 */
1680 /* cmp QWORD PTR [rbp - 0x8], 0x0 */
1681 EMIT4(0x48, 0x83, 0x7d, 0xf8); EMIT1(0x00);
1682
1683 /* Save the location of the branch and Generate 6 nops
1684 * (4 bytes for an offset and 2 bytes for the jump) These nops
1685 * are replaced with a conditional jump once do_fexit (i.e. the
1686 * start of the fexit invocation) is finalized.
1687 */
1688 branches[i] = prog;
1689 emit_nops(&prog, 4 + 2);
1690 }
1691
1692 *pprog = prog;
1693 return 0;
1694 }
1695
is_valid_bpf_tramp_flags(unsigned int flags)1696 static bool is_valid_bpf_tramp_flags(unsigned int flags)
1697 {
1698 if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
1699 (flags & BPF_TRAMP_F_SKIP_FRAME))
1700 return false;
1701
1702 /*
1703 * BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
1704 * and it must be used alone.
1705 */
1706 if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) &&
1707 (flags & ~BPF_TRAMP_F_RET_FENTRY_RET))
1708 return false;
1709
1710 return true;
1711 }
1712
1713 /* Example:
1714 * __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
1715 * its 'struct btf_func_model' will be nr_args=2
1716 * The assembly code when eth_type_trans is executing after trampoline:
1717 *
1718 * push rbp
1719 * mov rbp, rsp
1720 * sub rsp, 16 // space for skb and dev
1721 * push rbx // temp regs to pass start time
1722 * mov qword ptr [rbp - 16], rdi // save skb pointer to stack
1723 * mov qword ptr [rbp - 8], rsi // save dev pointer to stack
1724 * call __bpf_prog_enter // rcu_read_lock and preempt_disable
1725 * mov rbx, rax // remember start time in bpf stats are enabled
1726 * lea rdi, [rbp - 16] // R1==ctx of bpf prog
1727 * call addr_of_jited_FENTRY_prog
1728 * movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
1729 * mov rsi, rbx // prog start time
1730 * call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
1731 * mov rdi, qword ptr [rbp - 16] // restore skb pointer from stack
1732 * mov rsi, qword ptr [rbp - 8] // restore dev pointer from stack
1733 * pop rbx
1734 * leave
1735 * ret
1736 *
1737 * eth_type_trans has 5 byte nop at the beginning. These 5 bytes will be
1738 * replaced with 'call generated_bpf_trampoline'. When it returns
1739 * eth_type_trans will continue executing with original skb and dev pointers.
1740 *
1741 * The assembly code when eth_type_trans is called from trampoline:
1742 *
1743 * push rbp
1744 * mov rbp, rsp
1745 * sub rsp, 24 // space for skb, dev, return value
1746 * push rbx // temp regs to pass start time
1747 * mov qword ptr [rbp - 24], rdi // save skb pointer to stack
1748 * mov qword ptr [rbp - 16], rsi // save dev pointer to stack
1749 * call __bpf_prog_enter // rcu_read_lock and preempt_disable
1750 * mov rbx, rax // remember start time if bpf stats are enabled
1751 * lea rdi, [rbp - 24] // R1==ctx of bpf prog
1752 * call addr_of_jited_FENTRY_prog // bpf prog can access skb and dev
1753 * movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
1754 * mov rsi, rbx // prog start time
1755 * call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
1756 * mov rdi, qword ptr [rbp - 24] // restore skb pointer from stack
1757 * mov rsi, qword ptr [rbp - 16] // restore dev pointer from stack
1758 * call eth_type_trans+5 // execute body of eth_type_trans
1759 * mov qword ptr [rbp - 8], rax // save return value
1760 * call __bpf_prog_enter // rcu_read_lock and preempt_disable
1761 * mov rbx, rax // remember start time in bpf stats are enabled
1762 * lea rdi, [rbp - 24] // R1==ctx of bpf prog
1763 * call addr_of_jited_FEXIT_prog // bpf prog can access skb, dev, return value
1764 * movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
1765 * mov rsi, rbx // prog start time
1766 * call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
1767 * mov rax, qword ptr [rbp - 8] // restore eth_type_trans's return value
1768 * pop rbx
1769 * leave
1770 * add rsp, 8 // skip eth_type_trans's frame
1771 * ret // return to its caller
1772 */
arch_prepare_bpf_trampoline(struct bpf_tramp_image * im,void * image,void * image_end,const struct btf_func_model * m,u32 flags,struct bpf_tramp_progs * tprogs,void * orig_call)1773 int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
1774 const struct btf_func_model *m, u32 flags,
1775 struct bpf_tramp_progs *tprogs,
1776 void *orig_call)
1777 {
1778 int ret, i, cnt = 0, nr_args = m->nr_args;
1779 int stack_size = nr_args * 8;
1780 struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY];
1781 struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT];
1782 struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN];
1783 u8 **branches = NULL;
1784 u8 *prog;
1785 bool save_ret;
1786
1787 /* x86-64 supports up to 6 arguments. 7+ can be added in the future */
1788 if (nr_args > 6)
1789 return -ENOTSUPP;
1790
1791 if (!is_valid_bpf_tramp_flags(flags))
1792 return -EINVAL;
1793
1794 /* room for return value of orig_call or fentry prog */
1795 save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
1796 if (save_ret)
1797 stack_size += 8;
1798
1799 if (flags & BPF_TRAMP_F_SKIP_FRAME)
1800 /* skip patched call instruction and point orig_call to actual
1801 * body of the kernel function.
1802 */
1803 orig_call += X86_PATCH_SIZE;
1804
1805 prog = image;
1806
1807 EMIT1(0x55); /* push rbp */
1808 EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
1809 EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */
1810 EMIT1(0x53); /* push rbx */
1811
1812 save_regs(m, &prog, nr_args, stack_size);
1813
1814 if (flags & BPF_TRAMP_F_CALL_ORIG) {
1815 /* arg1: mov rdi, im */
1816 emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
1817 if (emit_call(&prog, __bpf_tramp_enter, prog)) {
1818 ret = -EINVAL;
1819 goto cleanup;
1820 }
1821 }
1822
1823 if (fentry->nr_progs)
1824 if (invoke_bpf(m, &prog, fentry, stack_size,
1825 flags & BPF_TRAMP_F_RET_FENTRY_RET))
1826 return -EINVAL;
1827
1828 if (fmod_ret->nr_progs) {
1829 branches = kcalloc(fmod_ret->nr_progs, sizeof(u8 *),
1830 GFP_KERNEL);
1831 if (!branches)
1832 return -ENOMEM;
1833
1834 if (invoke_bpf_mod_ret(m, &prog, fmod_ret, stack_size,
1835 branches)) {
1836 ret = -EINVAL;
1837 goto cleanup;
1838 }
1839 }
1840
1841 if (flags & BPF_TRAMP_F_CALL_ORIG) {
1842 restore_regs(m, &prog, nr_args, stack_size);
1843
1844 /* call original function */
1845 if (emit_call(&prog, orig_call, prog)) {
1846 ret = -EINVAL;
1847 goto cleanup;
1848 }
1849 /* remember return value in a stack for bpf prog to access */
1850 emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
1851 im->ip_after_call = prog;
1852 memcpy(prog, ideal_nops[NOP_ATOMIC5], X86_PATCH_SIZE);
1853 prog += X86_PATCH_SIZE;
1854 }
1855
1856 if (fmod_ret->nr_progs) {
1857 /* From Intel 64 and IA-32 Architectures Optimization
1858 * Reference Manual, 3.4.1.4 Code Alignment, Assembly/Compiler
1859 * Coding Rule 11: All branch targets should be 16-byte
1860 * aligned.
1861 */
1862 emit_align(&prog, 16);
1863 /* Update the branches saved in invoke_bpf_mod_ret with the
1864 * aligned address of do_fexit.
1865 */
1866 for (i = 0; i < fmod_ret->nr_progs; i++)
1867 emit_cond_near_jump(&branches[i], prog, branches[i],
1868 X86_JNE);
1869 }
1870
1871 if (fexit->nr_progs)
1872 if (invoke_bpf(m, &prog, fexit, stack_size, false)) {
1873 ret = -EINVAL;
1874 goto cleanup;
1875 }
1876
1877 if (flags & BPF_TRAMP_F_RESTORE_REGS)
1878 restore_regs(m, &prog, nr_args, stack_size);
1879
1880 /* This needs to be done regardless. If there were fmod_ret programs,
1881 * the return value is only updated on the stack and still needs to be
1882 * restored to R0.
1883 */
1884 if (flags & BPF_TRAMP_F_CALL_ORIG) {
1885 im->ip_epilogue = prog;
1886 /* arg1: mov rdi, im */
1887 emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
1888 if (emit_call(&prog, __bpf_tramp_exit, prog)) {
1889 ret = -EINVAL;
1890 goto cleanup;
1891 }
1892 }
1893 /* restore return value of orig_call or fentry prog back into RAX */
1894 if (save_ret)
1895 emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
1896
1897 EMIT1(0x5B); /* pop rbx */
1898 EMIT1(0xC9); /* leave */
1899 if (flags & BPF_TRAMP_F_SKIP_FRAME)
1900 /* skip our return address and return to parent */
1901 EMIT4(0x48, 0x83, 0xC4, 8); /* add rsp, 8 */
1902 emit_return(&prog, prog);
1903 /* Make sure the trampoline generation logic doesn't overflow */
1904 if (WARN_ON_ONCE(prog > (u8 *)image_end - BPF_INSN_SAFETY)) {
1905 ret = -EFAULT;
1906 goto cleanup;
1907 }
1908 ret = prog - (u8 *)image;
1909
1910 cleanup:
1911 kfree(branches);
1912 return ret;
1913 }
1914
emit_bpf_dispatcher(u8 ** pprog,int a,int b,s64 * progs)1915 static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs)
1916 {
1917 u8 *jg_reloc, *prog = *pprog;
1918 int pivot, err, jg_bytes = 1, cnt = 0;
1919 s64 jg_offset;
1920
1921 if (a == b) {
1922 /* Leaf node of recursion, i.e. not a range of indices
1923 * anymore.
1924 */
1925 EMIT1(add_1mod(0x48, BPF_REG_3)); /* cmp rdx,func */
1926 if (!is_simm32(progs[a]))
1927 return -1;
1928 EMIT2_off32(0x81, add_1reg(0xF8, BPF_REG_3),
1929 progs[a]);
1930 err = emit_cond_near_jump(&prog, /* je func */
1931 (void *)progs[a], prog,
1932 X86_JE);
1933 if (err)
1934 return err;
1935
1936 emit_indirect_jump(&prog, 2 /* rdx */, prog);
1937
1938 *pprog = prog;
1939 return 0;
1940 }
1941
1942 /* Not a leaf node, so we pivot, and recursively descend into
1943 * the lower and upper ranges.
1944 */
1945 pivot = (b - a) / 2;
1946 EMIT1(add_1mod(0x48, BPF_REG_3)); /* cmp rdx,func */
1947 if (!is_simm32(progs[a + pivot]))
1948 return -1;
1949 EMIT2_off32(0x81, add_1reg(0xF8, BPF_REG_3), progs[a + pivot]);
1950
1951 if (pivot > 2) { /* jg upper_part */
1952 /* Require near jump. */
1953 jg_bytes = 4;
1954 EMIT2_off32(0x0F, X86_JG + 0x10, 0);
1955 } else {
1956 EMIT2(X86_JG, 0);
1957 }
1958 jg_reloc = prog;
1959
1960 err = emit_bpf_dispatcher(&prog, a, a + pivot, /* emit lower_part */
1961 progs);
1962 if (err)
1963 return err;
1964
1965 /* From Intel 64 and IA-32 Architectures Optimization
1966 * Reference Manual, 3.4.1.4 Code Alignment, Assembly/Compiler
1967 * Coding Rule 11: All branch targets should be 16-byte
1968 * aligned.
1969 */
1970 emit_align(&prog, 16);
1971 jg_offset = prog - jg_reloc;
1972 emit_code(jg_reloc - jg_bytes, jg_offset, jg_bytes);
1973
1974 err = emit_bpf_dispatcher(&prog, a + pivot + 1, /* emit upper_part */
1975 b, progs);
1976 if (err)
1977 return err;
1978
1979 *pprog = prog;
1980 return 0;
1981 }
1982
cmp_ips(const void * a,const void * b)1983 static int cmp_ips(const void *a, const void *b)
1984 {
1985 const s64 *ipa = a;
1986 const s64 *ipb = b;
1987
1988 if (*ipa > *ipb)
1989 return 1;
1990 if (*ipa < *ipb)
1991 return -1;
1992 return 0;
1993 }
1994
arch_prepare_bpf_dispatcher(void * image,s64 * funcs,int num_funcs)1995 int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
1996 {
1997 u8 *prog = image;
1998
1999 sort(funcs, num_funcs, sizeof(funcs[0]), cmp_ips, NULL);
2000 return emit_bpf_dispatcher(&prog, 0, num_funcs - 1, funcs);
2001 }
2002
2003 struct x64_jit_data {
2004 struct bpf_binary_header *header;
2005 int *addrs;
2006 u8 *image;
2007 int proglen;
2008 struct jit_context ctx;
2009 };
2010
bpf_int_jit_compile(struct bpf_prog * prog)2011 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
2012 {
2013 struct bpf_binary_header *header = NULL;
2014 struct bpf_prog *tmp, *orig_prog = prog;
2015 struct x64_jit_data *jit_data;
2016 int proglen, oldproglen = 0;
2017 struct jit_context ctx = {};
2018 bool tmp_blinded = false;
2019 bool extra_pass = false;
2020 u8 *image = NULL;
2021 int *addrs;
2022 int pass;
2023 int i;
2024
2025 if (!prog->jit_requested)
2026 return orig_prog;
2027
2028 tmp = bpf_jit_blind_constants(prog);
2029 /*
2030 * If blinding was requested and we failed during blinding,
2031 * we must fall back to the interpreter.
2032 */
2033 if (IS_ERR(tmp))
2034 return orig_prog;
2035 if (tmp != prog) {
2036 tmp_blinded = true;
2037 prog = tmp;
2038 }
2039
2040 jit_data = prog->aux->jit_data;
2041 if (!jit_data) {
2042 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
2043 if (!jit_data) {
2044 prog = orig_prog;
2045 goto out;
2046 }
2047 prog->aux->jit_data = jit_data;
2048 }
2049 addrs = jit_data->addrs;
2050 if (addrs) {
2051 ctx = jit_data->ctx;
2052 oldproglen = jit_data->proglen;
2053 image = jit_data->image;
2054 header = jit_data->header;
2055 extra_pass = true;
2056 goto skip_init_addrs;
2057 }
2058 addrs = kvmalloc_array(prog->len + 1, sizeof(*addrs), GFP_KERNEL);
2059 if (!addrs) {
2060 prog = orig_prog;
2061 goto out_addrs;
2062 }
2063
2064 /*
2065 * Before first pass, make a rough estimation of addrs[]
2066 * each BPF instruction is translated to less than 64 bytes
2067 */
2068 for (proglen = 0, i = 0; i <= prog->len; i++) {
2069 proglen += 64;
2070 addrs[i] = proglen;
2071 }
2072 ctx.cleanup_addr = proglen;
2073 skip_init_addrs:
2074
2075 /*
2076 * JITed image shrinks with every pass and the loop iterates
2077 * until the image stops shrinking. Very large BPF programs
2078 * may converge on the last pass. In such case do one more
2079 * pass to emit the final image.
2080 */
2081 for (pass = 0; pass < 20 || image; pass++) {
2082 proglen = do_jit(prog, addrs, image, oldproglen, &ctx);
2083 if (proglen <= 0) {
2084 out_image:
2085 image = NULL;
2086 if (header)
2087 bpf_jit_binary_free(header);
2088 prog = orig_prog;
2089 goto out_addrs;
2090 }
2091 if (image) {
2092 if (proglen != oldproglen) {
2093 pr_err("bpf_jit: proglen=%d != oldproglen=%d\n",
2094 proglen, oldproglen);
2095 goto out_image;
2096 }
2097 break;
2098 }
2099 if (proglen == oldproglen) {
2100 /*
2101 * The number of entries in extable is the number of BPF_LDX
2102 * insns that access kernel memory via "pointer to BTF type".
2103 * The verifier changed their opcode from LDX|MEM|size
2104 * to LDX|PROBE_MEM|size to make JITing easier.
2105 */
2106 u32 align = __alignof__(struct exception_table_entry);
2107 u32 extable_size = prog->aux->num_exentries *
2108 sizeof(struct exception_table_entry);
2109
2110 /* allocate module memory for x86 insns and extable */
2111 header = bpf_jit_binary_alloc(roundup(proglen, align) + extable_size,
2112 &image, align, jit_fill_hole);
2113 if (!header) {
2114 prog = orig_prog;
2115 goto out_addrs;
2116 }
2117 prog->aux->extable = (void *) image + roundup(proglen, align);
2118 }
2119 oldproglen = proglen;
2120 cond_resched();
2121 }
2122
2123 if (bpf_jit_enable > 1)
2124 bpf_jit_dump(prog->len, proglen, pass + 1, image);
2125
2126 if (image) {
2127 if (!prog->is_func || extra_pass) {
2128 bpf_tail_call_direct_fixup(prog);
2129 bpf_jit_binary_lock_ro(header);
2130 } else {
2131 jit_data->addrs = addrs;
2132 jit_data->ctx = ctx;
2133 jit_data->proglen = proglen;
2134 jit_data->image = image;
2135 jit_data->header = header;
2136 }
2137 prog->bpf_func = (void *)image;
2138 prog->jited = 1;
2139 prog->jited_len = proglen;
2140 } else {
2141 prog = orig_prog;
2142 }
2143
2144 if (!image || !prog->is_func || extra_pass) {
2145 if (image)
2146 bpf_prog_fill_jited_linfo(prog, addrs + 1);
2147 out_addrs:
2148 kvfree(addrs);
2149 kfree(jit_data);
2150 prog->aux->jit_data = NULL;
2151 }
2152 out:
2153 if (tmp_blinded)
2154 bpf_jit_prog_release_other(prog, prog == orig_prog ?
2155 tmp : orig_prog);
2156 return prog;
2157 }
2158