1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #include <linux/jump_label.h> 3 #include <asm/unwind_hints.h> 4 5 /* 6 7 x86 function call convention, 64-bit: 8 ------------------------------------- 9 arguments | callee-saved | extra caller-saved | return 10 [callee-clobbered] | | [callee-clobbered] | 11 --------------------------------------------------------------------------- 12 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] 13 14 ( rsp is obviously invariant across normal function calls. (gcc can 'merge' 15 functions when it sees tail-call optimization possibilities) rflags is 16 clobbered. Leftover arguments are passed over the stack frame.) 17 18 [*] In the frame-pointers case rbp is fixed to the stack frame. 19 20 [**] for struct return values wider than 64 bits the return convention is a 21 bit more complex: up to 128 bits width we return small structures 22 straight in rax, rdx. For structures larger than that (3 words or 23 larger) the caller puts a pointer to an on-stack return struct 24 [allocated in the caller's stack frame] into the first argument - i.e. 25 into rdi. All other arguments shift up by one in this case. 26 Fortunately this case is rare in the kernel. 27 28 For 32-bit we have the following conventions - kernel is built with 29 -mregparm=3 and -freg-struct-return: 30 31 x86 function calling convention, 32-bit: 32 ---------------------------------------- 33 arguments | callee-saved | extra caller-saved | return 34 [callee-clobbered] | | [callee-clobbered] | 35 ------------------------------------------------------------------------- 36 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] 37 38 ( here too esp is obviously invariant across normal function calls. eflags 39 is clobbered. Leftover arguments are passed over the stack frame. ) 40 41 [*] In the frame-pointers case ebp is fixed to the stack frame. 42 43 [**] We build with -freg-struct-return, which on 32-bit means similar 44 semantics as on 64-bit: edx can be used for a second return value 45 (i.e. covering integer and structure sizes up to 64 bits) - after that 46 it gets more complex and more expensive: 3-word or larger struct returns 47 get done in the caller's frame and the pointer to the return struct goes 48 into regparm0, i.e. eax - the other arguments shift up and the 49 function's register parameters degenerate to regparm=2 in essence. 50 51 */ 52 53 #ifdef CONFIG_X86_64 54 55 /* 56 * 64-bit system call stack frame layout defines and helpers, 57 * for assembly code: 58 */ 59 60 /* The layout forms the "struct pt_regs" on the stack: */ 61 /* 62 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry 63 * unless syscall needs a complete, fully filled "struct pt_regs". 64 */ 65 #define R15 0*8 66 #define R14 1*8 67 #define R13 2*8 68 #define R12 3*8 69 #define RBP 4*8 70 #define RBX 5*8 71 /* These regs are callee-clobbered. Always saved on kernel entry. */ 72 #define R11 6*8 73 #define R10 7*8 74 #define R9 8*8 75 #define R8 9*8 76 #define RAX 10*8 77 #define RCX 11*8 78 #define RDX 12*8 79 #define RSI 13*8 80 #define RDI 14*8 81 /* 82 * On syscall entry, this is syscall#. On CPU exception, this is error code. 83 * On hw interrupt, it's IRQ number: 84 */ 85 #define ORIG_RAX 15*8 86 /* Return frame for iretq */ 87 #define RIP 16*8 88 #define CS 17*8 89 #define EFLAGS 18*8 90 #define RSP 19*8 91 #define SS 20*8 92 93 #define SIZEOF_PTREGS 21*8 94 95 .macro ALLOC_PT_GPREGS_ON_STACK 96 addq $-(15*8), %rsp 97 .endm 98 99 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1 100 .if \r11 101 movq %r11, 6*8+\offset(%rsp) 102 .endif 103 .if \r8910 104 movq %r10, 7*8+\offset(%rsp) 105 movq %r9, 8*8+\offset(%rsp) 106 movq %r8, 9*8+\offset(%rsp) 107 .endif 108 .if \rax 109 movq %rax, 10*8+\offset(%rsp) 110 .endif 111 .if \rcx 112 movq %rcx, 11*8+\offset(%rsp) 113 .endif 114 movq %rdx, 12*8+\offset(%rsp) 115 movq %rsi, 13*8+\offset(%rsp) 116 movq %rdi, 14*8+\offset(%rsp) 117 UNWIND_HINT_REGS offset=\offset extra=0 118 .endm 119 .macro SAVE_C_REGS offset=0 120 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1 121 .endm 122 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0 123 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1 124 .endm 125 .macro SAVE_C_REGS_EXCEPT_R891011 126 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0 127 .endm 128 .macro SAVE_C_REGS_EXCEPT_RCX_R891011 129 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0 130 .endm 131 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11 132 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0 133 .endm 134 135 .macro SAVE_EXTRA_REGS offset=0 136 movq %r15, 0*8+\offset(%rsp) 137 movq %r14, 1*8+\offset(%rsp) 138 movq %r13, 2*8+\offset(%rsp) 139 movq %r12, 3*8+\offset(%rsp) 140 movq %rbp, 4*8+\offset(%rsp) 141 movq %rbx, 5*8+\offset(%rsp) 142 UNWIND_HINT_REGS offset=\offset 143 .endm 144 145 .macro RESTORE_EXTRA_REGS offset=0 146 movq 0*8+\offset(%rsp), %r15 147 movq 1*8+\offset(%rsp), %r14 148 movq 2*8+\offset(%rsp), %r13 149 movq 3*8+\offset(%rsp), %r12 150 movq 4*8+\offset(%rsp), %rbp 151 movq 5*8+\offset(%rsp), %rbx 152 UNWIND_HINT_REGS offset=\offset extra=0 153 .endm 154 155 .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1 156 .if \rstor_r11 157 movq 6*8(%rsp), %r11 158 .endif 159 .if \rstor_r8910 160 movq 7*8(%rsp), %r10 161 movq 8*8(%rsp), %r9 162 movq 9*8(%rsp), %r8 163 .endif 164 .if \rstor_rax 165 movq 10*8(%rsp), %rax 166 .endif 167 .if \rstor_rcx 168 movq 11*8(%rsp), %rcx 169 .endif 170 .if \rstor_rdx 171 movq 12*8(%rsp), %rdx 172 .endif 173 movq 13*8(%rsp), %rsi 174 movq 14*8(%rsp), %rdi 175 UNWIND_HINT_IRET_REGS offset=16*8 176 .endm 177 .macro RESTORE_C_REGS 178 RESTORE_C_REGS_HELPER 1,1,1,1,1 179 .endm 180 .macro RESTORE_C_REGS_EXCEPT_RAX 181 RESTORE_C_REGS_HELPER 0,1,1,1,1 182 .endm 183 .macro RESTORE_C_REGS_EXCEPT_RCX 184 RESTORE_C_REGS_HELPER 1,0,1,1,1 185 .endm 186 .macro RESTORE_C_REGS_EXCEPT_R11 187 RESTORE_C_REGS_HELPER 1,1,0,1,1 188 .endm 189 .macro RESTORE_C_REGS_EXCEPT_RCX_R11 190 RESTORE_C_REGS_HELPER 1,0,0,1,1 191 .endm 192 193 .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0 194 subq $-(15*8+\addskip), %rsp 195 .endm 196 197 .macro icebp 198 .byte 0xf1 199 .endm 200 201 /* 202 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The 203 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding 204 * is just setting the LSB, which makes it an invalid stack address and is also 205 * a signal to the unwinder that it's a pt_regs pointer in disguise. 206 * 207 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts 208 * the original rbp. 209 */ 210 .macro ENCODE_FRAME_POINTER ptregs_offset=0 211 #ifdef CONFIG_FRAME_POINTER 212 .if \ptregs_offset 213 leaq \ptregs_offset(%rsp), %rbp 214 .else 215 mov %rsp, %rbp 216 .endif 217 orq $0x1, %rbp 218 #endif 219 .endm 220 221 #endif /* CONFIG_X86_64 */ 222 223 /* 224 * This does 'call enter_from_user_mode' unless we can avoid it based on 225 * kernel config or using the static jump infrastructure. 226 */ 227 .macro CALL_enter_from_user_mode 228 #ifdef CONFIG_CONTEXT_TRACKING 229 #ifdef HAVE_JUMP_LABEL 230 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0 231 #endif 232 call enter_from_user_mode 233 .Lafter_call_\@: 234 #endif 235 .endm 236