1 /* 2 3 x86 function call convention, 64-bit: 4 ------------------------------------- 5 arguments | callee-saved | extra caller-saved | return 6 [callee-clobbered] | | [callee-clobbered] | 7 --------------------------------------------------------------------------- 8 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] 9 10 ( rsp is obviously invariant across normal function calls. (gcc can 'merge' 11 functions when it sees tail-call optimization possibilities) rflags is 12 clobbered. Leftover arguments are passed over the stack frame.) 13 14 [*] In the frame-pointers case rbp is fixed to the stack frame. 15 16 [**] for struct return values wider than 64 bits the return convention is a 17 bit more complex: up to 128 bits width we return small structures 18 straight in rax, rdx. For structures larger than that (3 words or 19 larger) the caller puts a pointer to an on-stack return struct 20 [allocated in the caller's stack frame] into the first argument - i.e. 21 into rdi. All other arguments shift up by one in this case. 22 Fortunately this case is rare in the kernel. 23 24 For 32-bit we have the following conventions - kernel is built with 25 -mregparm=3 and -freg-struct-return: 26 27 x86 function calling convention, 32-bit: 28 ---------------------------------------- 29 arguments | callee-saved | extra caller-saved | return 30 [callee-clobbered] | | [callee-clobbered] | 31 ------------------------------------------------------------------------- 32 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] 33 34 ( here too esp is obviously invariant across normal function calls. eflags 35 is clobbered. Leftover arguments are passed over the stack frame. ) 36 37 [*] In the frame-pointers case ebp is fixed to the stack frame. 38 39 [**] We build with -freg-struct-return, which on 32-bit means similar 40 semantics as on 64-bit: edx can be used for a second return value 41 (i.e. covering integer and structure sizes up to 64 bits) - after that 42 it gets more complex and more expensive: 3-word or larger struct returns 43 get done in the caller's frame and the pointer to the return struct goes 44 into regparm0, i.e. eax - the other arguments shift up and the 45 function's register parameters degenerate to regparm=2 in essence. 46 47 */ 48 49 #include <asm/dwarf2.h> 50 51 #ifdef CONFIG_X86_64 52 53 /* 54 * 64-bit system call stack frame layout defines and helpers, 55 * for assembly code: 56 */ 57 58 #define R15 0 59 #define R14 8 60 #define R13 16 61 #define R12 24 62 #define RBP 32 63 #define RBX 40 64 65 /* arguments: interrupts/non tracing syscalls only save up to here: */ 66 #define R11 48 67 #define R10 56 68 #define R9 64 69 #define R8 72 70 #define RAX 80 71 #define RCX 88 72 #define RDX 96 73 #define RSI 104 74 #define RDI 112 75 #define ORIG_RAX 120 /* + error_code */ 76 /* end of arguments */ 77 78 /* cpu exception frame or undefined in case of fast syscall: */ 79 #define RIP 128 80 #define CS 136 81 #define EFLAGS 144 82 #define RSP 152 83 #define SS 160 84 85 #define ARGOFFSET R11 86 #define SWFRAME ORIG_RAX 87 88 .macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1, rax_enosys=0 89 subq $9*8+\addskip, %rsp 90 CFI_ADJUST_CFA_OFFSET 9*8+\addskip 91 movq_cfi rdi, 8*8 92 movq_cfi rsi, 7*8 93 movq_cfi rdx, 6*8 94 95 .if \save_rcx 96 movq_cfi rcx, 5*8 97 .endif 98 99 .if \rax_enosys 100 movq $-ENOSYS, 4*8(%rsp) 101 .else 102 movq_cfi rax, 4*8 103 .endif 104 105 .if \save_r891011 106 movq_cfi r8, 3*8 107 movq_cfi r9, 2*8 108 movq_cfi r10, 1*8 109 movq_cfi r11, 0*8 110 .endif 111 112 .endm 113 114 #define ARG_SKIP (9*8) 115 116 .macro RESTORE_ARGS rstor_rax=1, addskip=0, rstor_rcx=1, rstor_r11=1, \ 117 rstor_r8910=1, rstor_rdx=1 118 .if \rstor_r11 119 movq_cfi_restore 0*8, r11 120 .endif 121 122 .if \rstor_r8910 123 movq_cfi_restore 1*8, r10 124 movq_cfi_restore 2*8, r9 125 movq_cfi_restore 3*8, r8 126 .endif 127 128 .if \rstor_rax 129 movq_cfi_restore 4*8, rax 130 .endif 131 132 .if \rstor_rcx 133 movq_cfi_restore 5*8, rcx 134 .endif 135 136 .if \rstor_rdx 137 movq_cfi_restore 6*8, rdx 138 .endif 139 140 movq_cfi_restore 7*8, rsi 141 movq_cfi_restore 8*8, rdi 142 143 .if ARG_SKIP+\addskip > 0 144 addq $ARG_SKIP+\addskip, %rsp 145 CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip) 146 .endif 147 .endm 148 149 .macro LOAD_ARGS offset, skiprax=0 150 movq \offset(%rsp), %r11 151 movq \offset+8(%rsp), %r10 152 movq \offset+16(%rsp), %r9 153 movq \offset+24(%rsp), %r8 154 movq \offset+40(%rsp), %rcx 155 movq \offset+48(%rsp), %rdx 156 movq \offset+56(%rsp), %rsi 157 movq \offset+64(%rsp), %rdi 158 .if \skiprax 159 .else 160 movq \offset+72(%rsp), %rax 161 .endif 162 .endm 163 164 #define REST_SKIP (6*8) 165 166 .macro SAVE_REST 167 subq $REST_SKIP, %rsp 168 CFI_ADJUST_CFA_OFFSET REST_SKIP 169 movq_cfi rbx, 5*8 170 movq_cfi rbp, 4*8 171 movq_cfi r12, 3*8 172 movq_cfi r13, 2*8 173 movq_cfi r14, 1*8 174 movq_cfi r15, 0*8 175 .endm 176 177 .macro RESTORE_REST 178 movq_cfi_restore 0*8, r15 179 movq_cfi_restore 1*8, r14 180 movq_cfi_restore 2*8, r13 181 movq_cfi_restore 3*8, r12 182 movq_cfi_restore 4*8, rbp 183 movq_cfi_restore 5*8, rbx 184 addq $REST_SKIP, %rsp 185 CFI_ADJUST_CFA_OFFSET -(REST_SKIP) 186 .endm 187 188 .macro SAVE_ALL 189 SAVE_ARGS 190 SAVE_REST 191 .endm 192 193 .macro RESTORE_ALL addskip=0 194 RESTORE_REST 195 RESTORE_ARGS 1, \addskip 196 .endm 197 198 .macro icebp 199 .byte 0xf1 200 .endm 201 202 #else /* CONFIG_X86_64 */ 203 204 /* 205 * For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These 206 * are different from the entry_32.S versions in not changing the segment 207 * registers. So only suitable for in kernel use, not when transitioning 208 * from or to user space. The resulting stack frame is not a standard 209 * pt_regs frame. The main use case is calling C code from assembler 210 * when all the registers need to be preserved. 211 */ 212 213 .macro SAVE_ALL 214 pushl_cfi %eax 215 CFI_REL_OFFSET eax, 0 216 pushl_cfi %ebp 217 CFI_REL_OFFSET ebp, 0 218 pushl_cfi %edi 219 CFI_REL_OFFSET edi, 0 220 pushl_cfi %esi 221 CFI_REL_OFFSET esi, 0 222 pushl_cfi %edx 223 CFI_REL_OFFSET edx, 0 224 pushl_cfi %ecx 225 CFI_REL_OFFSET ecx, 0 226 pushl_cfi %ebx 227 CFI_REL_OFFSET ebx, 0 228 .endm 229 230 .macro RESTORE_ALL 231 popl_cfi %ebx 232 CFI_RESTORE ebx 233 popl_cfi %ecx 234 CFI_RESTORE ecx 235 popl_cfi %edx 236 CFI_RESTORE edx 237 popl_cfi %esi 238 CFI_RESTORE esi 239 popl_cfi %edi 240 CFI_RESTORE edi 241 popl_cfi %ebp 242 CFI_RESTORE ebp 243 popl_cfi %eax 244 CFI_RESTORE eax 245 .endm 246 247 #endif /* CONFIG_X86_64 */ 248 249