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 POP_EXTRA_REGS 145 popq %r15 146 popq %r14 147 popq %r13 148 popq %r12 149 popq %rbp 150 popq %rbx 151 .endm 152 153 .macro POP_C_REGS 154 popq %r11 155 popq %r10 156 popq %r9 157 popq %r8 158 popq %rax 159 popq %rcx 160 popq %rdx 161 popq %rsi 162 popq %rdi 163 .endm 164 165 .macro icebp 166 .byte 0xf1 167 .endm 168 169 /* 170 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The 171 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding 172 * is just setting the LSB, which makes it an invalid stack address and is also 173 * a signal to the unwinder that it's a pt_regs pointer in disguise. 174 * 175 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts 176 * the original rbp. 177 */ 178 .macro ENCODE_FRAME_POINTER ptregs_offset=0 179 #ifdef CONFIG_FRAME_POINTER 180 .if \ptregs_offset 181 leaq \ptregs_offset(%rsp), %rbp 182 .else 183 mov %rsp, %rbp 184 .endif 185 orq $0x1, %rbp 186 #endif 187 .endm 188 189 #endif /* CONFIG_X86_64 */ 190 191 /* 192 * This does 'call enter_from_user_mode' unless we can avoid it based on 193 * kernel config or using the static jump infrastructure. 194 */ 195 .macro CALL_enter_from_user_mode 196 #ifdef CONFIG_CONTEXT_TRACKING 197 #ifdef HAVE_JUMP_LABEL 198 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0 199 #endif 200 call enter_from_user_mode 201 .Lafter_call_\@: 202 #endif 203 .endm 204