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 /* The layout forms the "struct pt_regs" on the stack: */ 59 /* 60 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry 61 * unless syscall needs a complete, fully filled "struct pt_regs". 62 */ 63 #define R15 0*8 64 #define R14 1*8 65 #define R13 2*8 66 #define R12 3*8 67 #define RBP 4*8 68 #define RBX 5*8 69 /* These regs are callee-clobbered. Always saved on kernel entry. */ 70 #define R11 6*8 71 #define R10 7*8 72 #define R9 8*8 73 #define R8 9*8 74 #define RAX 10*8 75 #define RCX 11*8 76 #define RDX 12*8 77 #define RSI 13*8 78 #define RDI 14*8 79 /* 80 * On syscall entry, this is syscall#. On CPU exception, this is error code. 81 * On hw interrupt, it's IRQ number: 82 */ 83 #define ORIG_RAX 15*8 84 /* Return frame for iretq */ 85 #define RIP 16*8 86 #define CS 17*8 87 #define EFLAGS 18*8 88 #define RSP 19*8 89 #define SS 20*8 90 91 #define SIZEOF_PTREGS 21*8 92 93 .macro ALLOC_PT_GPREGS_ON_STACK addskip=0 94 subq $15*8+\addskip, %rsp 95 CFI_ADJUST_CFA_OFFSET 15*8+\addskip 96 .endm 97 98 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1 99 .if \r11 100 movq_cfi r11, 6*8+\offset 101 .endif 102 .if \r8910 103 movq_cfi r10, 7*8+\offset 104 movq_cfi r9, 8*8+\offset 105 movq_cfi r8, 9*8+\offset 106 .endif 107 .if \rax 108 movq_cfi rax, 10*8+\offset 109 .endif 110 .if \rcx 111 movq_cfi rcx, 11*8+\offset 112 .endif 113 movq_cfi rdx, 12*8+\offset 114 movq_cfi rsi, 13*8+\offset 115 movq_cfi rdi, 14*8+\offset 116 .endm 117 .macro SAVE_C_REGS offset=0 118 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1 119 .endm 120 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0 121 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1 122 .endm 123 .macro SAVE_C_REGS_EXCEPT_R891011 124 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0 125 .endm 126 .macro SAVE_C_REGS_EXCEPT_RCX_R891011 127 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0 128 .endm 129 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11 130 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0 131 .endm 132 133 .macro SAVE_EXTRA_REGS offset=0 134 movq_cfi r15, 0*8+\offset 135 movq_cfi r14, 1*8+\offset 136 movq_cfi r13, 2*8+\offset 137 movq_cfi r12, 3*8+\offset 138 movq_cfi rbp, 4*8+\offset 139 movq_cfi rbx, 5*8+\offset 140 .endm 141 .macro SAVE_EXTRA_REGS_RBP offset=0 142 movq_cfi rbp, 4*8+\offset 143 .endm 144 145 .macro RESTORE_EXTRA_REGS offset=0 146 movq_cfi_restore 0*8+\offset, r15 147 movq_cfi_restore 1*8+\offset, r14 148 movq_cfi_restore 2*8+\offset, r13 149 movq_cfi_restore 3*8+\offset, r12 150 movq_cfi_restore 4*8+\offset, rbp 151 movq_cfi_restore 5*8+\offset, rbx 152 .endm 153 154 .macro ZERO_EXTRA_REGS 155 xorl %r15d, %r15d 156 xorl %r14d, %r14d 157 xorl %r13d, %r13d 158 xorl %r12d, %r12d 159 xorl %ebp, %ebp 160 xorl %ebx, %ebx 161 .endm 162 163 .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1 164 .if \rstor_r11 165 movq_cfi_restore 6*8, r11 166 .endif 167 .if \rstor_r8910 168 movq_cfi_restore 7*8, r10 169 movq_cfi_restore 8*8, r9 170 movq_cfi_restore 9*8, r8 171 .endif 172 .if \rstor_rax 173 movq_cfi_restore 10*8, rax 174 .endif 175 .if \rstor_rcx 176 movq_cfi_restore 11*8, rcx 177 .endif 178 .if \rstor_rdx 179 movq_cfi_restore 12*8, rdx 180 .endif 181 movq_cfi_restore 13*8, rsi 182 movq_cfi_restore 14*8, rdi 183 .endm 184 .macro RESTORE_C_REGS 185 RESTORE_C_REGS_HELPER 1,1,1,1,1 186 .endm 187 .macro RESTORE_C_REGS_EXCEPT_RAX 188 RESTORE_C_REGS_HELPER 0,1,1,1,1 189 .endm 190 .macro RESTORE_C_REGS_EXCEPT_RCX 191 RESTORE_C_REGS_HELPER 1,0,1,1,1 192 .endm 193 .macro RESTORE_C_REGS_EXCEPT_R11 194 RESTORE_C_REGS_HELPER 1,1,0,1,1 195 .endm 196 .macro RESTORE_C_REGS_EXCEPT_RCX_R11 197 RESTORE_C_REGS_HELPER 1,0,0,1,1 198 .endm 199 .macro RESTORE_RSI_RDI 200 RESTORE_C_REGS_HELPER 0,0,0,0,0 201 .endm 202 .macro RESTORE_RSI_RDI_RDX 203 RESTORE_C_REGS_HELPER 0,0,0,0,1 204 .endm 205 206 .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0 207 addq $15*8+\addskip, %rsp 208 CFI_ADJUST_CFA_OFFSET -(15*8+\addskip) 209 .endm 210 211 .macro icebp 212 .byte 0xf1 213 .endm 214 215 #else /* CONFIG_X86_64 */ 216 217 /* 218 * For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These 219 * are different from the entry_32.S versions in not changing the segment 220 * registers. So only suitable for in kernel use, not when transitioning 221 * from or to user space. The resulting stack frame is not a standard 222 * pt_regs frame. The main use case is calling C code from assembler 223 * when all the registers need to be preserved. 224 */ 225 226 .macro SAVE_ALL 227 pushl_cfi_reg eax 228 pushl_cfi_reg ebp 229 pushl_cfi_reg edi 230 pushl_cfi_reg esi 231 pushl_cfi_reg edx 232 pushl_cfi_reg ecx 233 pushl_cfi_reg ebx 234 .endm 235 236 .macro RESTORE_ALL 237 popl_cfi_reg ebx 238 popl_cfi_reg ecx 239 popl_cfi_reg edx 240 popl_cfi_reg esi 241 popl_cfi_reg edi 242 popl_cfi_reg ebp 243 popl_cfi_reg eax 244 .endm 245 246 #endif /* CONFIG_X86_64 */ 247 248