1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
3
4 #include <linux/ftrace.h>
5 #include <linux/uaccess.h>
6 #include <asm/cacheflush.h>
7
8 #ifdef CONFIG_DYNAMIC_FTRACE
9
10 #define NOP 0x4000
11 #define NOP32_HI 0xc400
12 #define NOP32_LO 0x4820
13 #define PUSH_LR 0x14d0
14 #define MOVIH_LINK 0xea3a
15 #define ORI_LINK 0xef5a
16 #define JSR_LINK 0xe8fa
17 #define BSR_LINK 0xe000
18
19 /*
20 * Gcc-csky with -pg will insert stub in function prologue:
21 * push lr
22 * jbsr _mcount
23 * nop32
24 * nop32
25 *
26 * If the (callee - current_pc) is less then 64MB, we'll use bsr:
27 * push lr
28 * bsr _mcount
29 * nop32
30 * nop32
31 * else we'll use (movih + ori + jsr):
32 * push lr
33 * movih r26, ...
34 * ori r26, ...
35 * jsr r26
36 *
37 * (r26 is our reserved link-reg)
38 *
39 */
make_jbsr(unsigned long callee,unsigned long pc,uint16_t * call,bool nolr)40 static inline void make_jbsr(unsigned long callee, unsigned long pc,
41 uint16_t *call, bool nolr)
42 {
43 long offset;
44
45 call[0] = nolr ? NOP : PUSH_LR;
46
47 offset = (long) callee - (long) pc;
48
49 if (unlikely(offset < -67108864 || offset > 67108864)) {
50 call[1] = MOVIH_LINK;
51 call[2] = callee >> 16;
52 call[3] = ORI_LINK;
53 call[4] = callee & 0xffff;
54 call[5] = JSR_LINK;
55 call[6] = 0;
56 } else {
57 offset = offset >> 1;
58
59 call[1] = BSR_LINK |
60 ((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
61 call[2] = (uint16_t)((unsigned long) offset & 0xffff);
62 call[3] = call[5] = NOP32_HI;
63 call[4] = call[6] = NOP32_LO;
64 }
65 }
66
67 static uint16_t nops[7] = {NOP, NOP32_HI, NOP32_LO, NOP32_HI, NOP32_LO,
68 NOP32_HI, NOP32_LO};
ftrace_check_current_nop(unsigned long hook)69 static int ftrace_check_current_nop(unsigned long hook)
70 {
71 uint16_t olds[7];
72 unsigned long hook_pos = hook - 2;
73
74 if (probe_kernel_read((void *)olds, (void *)hook_pos, sizeof(nops)))
75 return -EFAULT;
76
77 if (memcmp((void *)nops, (void *)olds, sizeof(nops))) {
78 pr_err("%p: nop but get (%04x %04x %04x %04x %04x %04x %04x)\n",
79 (void *)hook_pos,
80 olds[0], olds[1], olds[2], olds[3], olds[4], olds[5],
81 olds[6]);
82
83 return -EINVAL;
84 }
85
86 return 0;
87 }
88
ftrace_modify_code(unsigned long hook,unsigned long target,bool enable,bool nolr)89 static int ftrace_modify_code(unsigned long hook, unsigned long target,
90 bool enable, bool nolr)
91 {
92 uint16_t call[7];
93
94 unsigned long hook_pos = hook - 2;
95 int ret = 0;
96
97 make_jbsr(target, hook, call, nolr);
98
99 ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
100 sizeof(nops));
101 if (ret)
102 return -EPERM;
103
104 flush_icache_range(hook_pos, hook_pos + MCOUNT_INSN_SIZE);
105
106 return 0;
107 }
108
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)109 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
110 {
111 int ret = ftrace_check_current_nop(rec->ip);
112
113 if (ret)
114 return ret;
115
116 return ftrace_modify_code(rec->ip, addr, true, false);
117 }
118
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)119 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
120 unsigned long addr)
121 {
122 return ftrace_modify_code(rec->ip, addr, false, false);
123 }
124
ftrace_update_ftrace_func(ftrace_func_t func)125 int ftrace_update_ftrace_func(ftrace_func_t func)
126 {
127 int ret = ftrace_modify_code((unsigned long)&ftrace_call,
128 (unsigned long)func, true, true);
129 return ret;
130 }
131
ftrace_dyn_arch_init(void)132 int __init ftrace_dyn_arch_init(void)
133 {
134 return 0;
135 }
136 #endif /* CONFIG_DYNAMIC_FTRACE */
137
138 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
prepare_ftrace_return(unsigned long * parent,unsigned long self_addr,unsigned long frame_pointer)139 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
140 unsigned long frame_pointer)
141 {
142 unsigned long return_hooker = (unsigned long)&return_to_handler;
143 unsigned long old;
144
145 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
146 return;
147
148 old = *parent;
149
150 if (!function_graph_enter(old, self_addr,
151 *(unsigned long *)frame_pointer, parent)) {
152 /*
153 * For csky-gcc function has sub-call:
154 * subi sp, sp, 8
155 * stw r8, (sp, 0)
156 * mov r8, sp
157 * st.w r15, (sp, 0x4)
158 * push r15
159 * jl _mcount
160 * We only need set *parent for resume
161 *
162 * For csky-gcc function has no sub-call:
163 * subi sp, sp, 4
164 * stw r8, (sp, 0)
165 * mov r8, sp
166 * push r15
167 * jl _mcount
168 * We need set *parent and *(frame_pointer + 4) for resume,
169 * because lr is resumed twice.
170 */
171 *parent = return_hooker;
172 frame_pointer += 4;
173 if (*(unsigned long *)frame_pointer == old)
174 *(unsigned long *)frame_pointer = return_hooker;
175 }
176 }
177
178 #ifdef CONFIG_DYNAMIC_FTRACE
ftrace_enable_ftrace_graph_caller(void)179 int ftrace_enable_ftrace_graph_caller(void)
180 {
181 return ftrace_modify_code((unsigned long)&ftrace_graph_call,
182 (unsigned long)&ftrace_graph_caller, true, true);
183 }
184
ftrace_disable_ftrace_graph_caller(void)185 int ftrace_disable_ftrace_graph_caller(void)
186 {
187 return ftrace_modify_code((unsigned long)&ftrace_graph_call,
188 (unsigned long)&ftrace_graph_caller, false, true);
189 }
190 #endif /* CONFIG_DYNAMIC_FTRACE */
191 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
192
193 /* _mcount is defined in abi's mcount.S */
194 EXPORT_SYMBOL(_mcount);
195