1 #include <linux/jump_label.h> 2 #include <asm/unwind_hints.h> 3 4 /* 5 6 x86 function call convention, 64-bit: 7 ------------------------------------- 8 arguments | callee-saved | extra caller-saved | return 9 [callee-clobbered] | | [callee-clobbered] | 10 --------------------------------------------------------------------------- 11 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] 12 13 ( rsp is obviously invariant across normal function calls. (gcc can 'merge' 14 functions when it sees tail-call optimization possibilities) rflags is 15 clobbered. Leftover arguments are passed over the stack frame.) 16 17 [*] In the frame-pointers case rbp is fixed to the stack frame. 18 19 [**] for struct return values wider than 64 bits the return convention is a 20 bit more complex: up to 128 bits width we return small structures 21 straight in rax, rdx. For structures larger than that (3 words or 22 larger) the caller puts a pointer to an on-stack return struct 23 [allocated in the caller's stack frame] into the first argument - i.e. 24 into rdi. All other arguments shift up by one in this case. 25 Fortunately this case is rare in the kernel. 26 27 For 32-bit we have the following conventions - kernel is built with 28 -mregparm=3 and -freg-struct-return: 29 30 x86 function calling convention, 32-bit: 31 ---------------------------------------- 32 arguments | callee-saved | extra caller-saved | return 33 [callee-clobbered] | | [callee-clobbered] | 34 ------------------------------------------------------------------------- 35 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] 36 37 ( here too esp is obviously invariant across normal function calls. eflags 38 is clobbered. Leftover arguments are passed over the stack frame. ) 39 40 [*] In the frame-pointers case ebp is fixed to the stack frame. 41 42 [**] We build with -freg-struct-return, which on 32-bit means similar 43 semantics as on 64-bit: edx can be used for a second return value 44 (i.e. covering integer and structure sizes up to 64 bits) - after that 45 it gets more complex and more expensive: 3-word or larger struct returns 46 get done in the caller's frame and the pointer to the return struct goes 47 into regparm0, i.e. eax - the other arguments shift up and the 48 function's register parameters degenerate to regparm=2 in essence. 49 50 */ 51 52 #ifdef CONFIG_X86_64 53 54 /* 55 * 64-bit system call stack frame layout defines and helpers, 56 * for assembly code: 57 */ 58 59 /* The layout forms the "struct pt_regs" on the stack: */ 60 /* 61 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry 62 * unless syscall needs a complete, fully filled "struct pt_regs". 63 */ 64 #define R15 0*8 65 #define R14 1*8 66 #define R13 2*8 67 #define R12 3*8 68 #define RBP 4*8 69 #define RBX 5*8 70 /* These regs are callee-clobbered. Always saved on kernel entry. */ 71 #define R11 6*8 72 #define R10 7*8 73 #define R9 8*8 74 #define R8 9*8 75 #define RAX 10*8 76 #define RCX 11*8 77 #define RDX 12*8 78 #define RSI 13*8 79 #define RDI 14*8 80 /* 81 * On syscall entry, this is syscall#. On CPU exception, this is error code. 82 * On hw interrupt, it's IRQ number: 83 */ 84 #define ORIG_RAX 15*8 85 /* Return frame for iretq */ 86 #define RIP 16*8 87 #define CS 17*8 88 #define EFLAGS 18*8 89 #define RSP 19*8 90 #define SS 20*8 91 92 #define SIZEOF_PTREGS 21*8 93 94 .macro ALLOC_PT_GPREGS_ON_STACK 95 addq $-(15*8), %rsp 96 .endm 97 98 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1 99 .if \r11 100 movq %r11, 6*8+\offset(%rsp) 101 .endif 102 .if \r8910 103 movq %r10, 7*8+\offset(%rsp) 104 movq %r9, 8*8+\offset(%rsp) 105 movq %r8, 9*8+\offset(%rsp) 106 .endif 107 .if \rax 108 movq %rax, 10*8+\offset(%rsp) 109 .endif 110 .if \rcx 111 movq %rcx, 11*8+\offset(%rsp) 112 .endif 113 movq %rdx, 12*8+\offset(%rsp) 114 movq %rsi, 13*8+\offset(%rsp) 115 movq %rdi, 14*8+\offset(%rsp) 116 UNWIND_HINT_REGS offset=\offset extra=0 117 .endm 118 .macro SAVE_C_REGS offset=0 119 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1 120 .endm 121 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0 122 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1 123 .endm 124 .macro SAVE_C_REGS_EXCEPT_R891011 125 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0 126 .endm 127 .macro SAVE_C_REGS_EXCEPT_RCX_R891011 128 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0 129 .endm 130 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11 131 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0 132 .endm 133 134 .macro SAVE_EXTRA_REGS offset=0 135 movq %r15, 0*8+\offset(%rsp) 136 movq %r14, 1*8+\offset(%rsp) 137 movq %r13, 2*8+\offset(%rsp) 138 movq %r12, 3*8+\offset(%rsp) 139 movq %rbp, 4*8+\offset(%rsp) 140 movq %rbx, 5*8+\offset(%rsp) 141 UNWIND_HINT_REGS offset=\offset 142 .endm 143 144 .macro RESTORE_EXTRA_REGS offset=0 145 movq 0*8+\offset(%rsp), %r15 146 movq 1*8+\offset(%rsp), %r14 147 movq 2*8+\offset(%rsp), %r13 148 movq 3*8+\offset(%rsp), %r12 149 movq 4*8+\offset(%rsp), %rbp 150 movq 5*8+\offset(%rsp), %rbx 151 UNWIND_HINT_REGS offset=\offset extra=0 152 .endm 153 154 .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1 155 .if \rstor_r11 156 movq 6*8(%rsp), %r11 157 .endif 158 .if \rstor_r8910 159 movq 7*8(%rsp), %r10 160 movq 8*8(%rsp), %r9 161 movq 9*8(%rsp), %r8 162 .endif 163 .if \rstor_rax 164 movq 10*8(%rsp), %rax 165 .endif 166 .if \rstor_rcx 167 movq 11*8(%rsp), %rcx 168 .endif 169 .if \rstor_rdx 170 movq 12*8(%rsp), %rdx 171 .endif 172 movq 13*8(%rsp), %rsi 173 movq 14*8(%rsp), %rdi 174 UNWIND_HINT_IRET_REGS offset=16*8 175 .endm 176 .macro RESTORE_C_REGS 177 RESTORE_C_REGS_HELPER 1,1,1,1,1 178 .endm 179 .macro RESTORE_C_REGS_EXCEPT_RAX 180 RESTORE_C_REGS_HELPER 0,1,1,1,1 181 .endm 182 .macro RESTORE_C_REGS_EXCEPT_RCX 183 RESTORE_C_REGS_HELPER 1,0,1,1,1 184 .endm 185 .macro RESTORE_C_REGS_EXCEPT_R11 186 RESTORE_C_REGS_HELPER 1,1,0,1,1 187 .endm 188 .macro RESTORE_C_REGS_EXCEPT_RCX_R11 189 RESTORE_C_REGS_HELPER 1,0,0,1,1 190 .endm 191 192 .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0 193 subq $-(15*8+\addskip), %rsp 194 .endm 195 196 .macro icebp 197 .byte 0xf1 198 .endm 199 200 /* 201 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The 202 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding 203 * is just setting the LSB, which makes it an invalid stack address and is also 204 * a signal to the unwinder that it's a pt_regs pointer in disguise. 205 * 206 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts 207 * the original rbp. 208 */ 209 .macro ENCODE_FRAME_POINTER ptregs_offset=0 210 #ifdef CONFIG_FRAME_POINTER 211 .if \ptregs_offset 212 leaq \ptregs_offset(%rsp), %rbp 213 .else 214 mov %rsp, %rbp 215 .endif 216 orq $0x1, %rbp 217 #endif 218 .endm 219 220 #endif /* CONFIG_X86_64 */ 221 222 /* 223 * This does 'call enter_from_user_mode' unless we can avoid it based on 224 * kernel config or using the static jump infrastructure. 225 */ 226 .macro CALL_enter_from_user_mode 227 #ifdef CONFIG_CONTEXT_TRACKING 228 #ifdef HAVE_JUMP_LABEL 229 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0 230 #endif 231 call enter_from_user_mode 232 .Lafter_call_\@: 233 #endif 234 .endm 235