blob: 0fa67503391257d89d1b55016c07e97fba7fa667 [file] [log] [blame]
x86 function call convention, 64-bit:
arguments | callee-saved | extra caller-saved | return
[callee-clobbered] | | [callee-clobbered] |
rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
( rsp is obviously invariant across normal function calls. (gcc can 'merge'
functions when it sees tail-call optimization possibilities) rflags is
clobbered. Leftover arguments are passed over the stack frame.)
[*] In the frame-pointers case rbp is fixed to the stack frame.
[**] for struct return values wider than 64 bits the return convention is a
bit more complex: up to 128 bits width we return small structures
straight in rax, rdx. For structures larger than that (3 words or
larger) the caller puts a pointer to an on-stack return struct
[allocated in the caller's stack frame] into the first argument - i.e.
into rdi. All other arguments shift up by one in this case.
Fortunately this case is rare in the kernel.
For 32-bit we have the following conventions - kernel is built with
-mregparm=3 and -freg-struct-return:
x86 function calling convention, 32-bit:
arguments | callee-saved | extra caller-saved | return
[callee-clobbered] | | [callee-clobbered] |
eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
( here too esp is obviously invariant across normal function calls. eflags
is clobbered. Leftover arguments are passed over the stack frame. )
[*] In the frame-pointers case ebp is fixed to the stack frame.
[**] We build with -freg-struct-return, which on 32-bit means similar
semantics as on 64-bit: edx can be used for a second return value
(i.e. covering integer and structure sizes up to 64 bits) - after that
it gets more complex and more expensive: 3-word or larger struct returns
get done in the caller's frame and the pointer to the return struct goes
into regparm0, i.e. eax - the other arguments shift up and the
function's register parameters degenerate to regparm=2 in essence.
#include <asm/dwarf2.h>
* 64-bit system call stack frame layout defines and helpers,
* for assembly code:
#define R15 0
#define R14 8
#define R13 16
#define R12 24
#define RBP 32
#define RBX 40
/* arguments: interrupts/non tracing syscalls only save up to here: */
#define R11 48
#define R10 56
#define R9 64
#define R8 72
#define RAX 80
#define RCX 88
#define RDX 96
#define RSI 104
#define RDI 112
#define ORIG_RAX 120 /* + error_code */
/* end of arguments */
/* cpu exception frame or undefined in case of fast syscall: */
#define RIP 128
#define CS 136
#define EFLAGS 144
#define RSP 152
#define SS 160
#define ARGOFFSET R11
.macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1
subq $9*8+\addskip, %rsp
movq_cfi rdi, 8*8
movq_cfi rsi, 7*8
movq_cfi rdx, 6*8
.if \save_rcx
movq_cfi rcx, 5*8
movq_cfi rax, 4*8
.if \save_r891011
movq_cfi r8, 3*8
movq_cfi r9, 2*8
movq_cfi r10, 1*8
movq_cfi r11, 0*8
#define ARG_SKIP (9*8)
.macro RESTORE_ARGS rstor_rax=1, addskip=0, rstor_rcx=1, rstor_r11=1, \
rstor_r8910=1, rstor_rdx=1
.if \rstor_r11
movq_cfi_restore 0*8, r11
.if \rstor_r8910
movq_cfi_restore 1*8, r10
movq_cfi_restore 2*8, r9
movq_cfi_restore 3*8, r8
.if \rstor_rax
movq_cfi_restore 4*8, rax
.if \rstor_rcx
movq_cfi_restore 5*8, rcx
.if \rstor_rdx
movq_cfi_restore 6*8, rdx
movq_cfi_restore 7*8, rsi
movq_cfi_restore 8*8, rdi
.if ARG_SKIP+\addskip > 0
addq $ARG_SKIP+\addskip, %rsp
.macro LOAD_ARGS offset, skiprax=0
movq \offset(%rsp), %r11
movq \offset+8(%rsp), %r10
movq \offset+16(%rsp), %r9
movq \offset+24(%rsp), %r8
movq \offset+40(%rsp), %rcx
movq \offset+48(%rsp), %rdx
movq \offset+56(%rsp), %rsi
movq \offset+64(%rsp), %rdi
.if \skiprax
movq \offset+72(%rsp), %rax
#define REST_SKIP (6*8)
.macro SAVE_REST
subq $REST_SKIP, %rsp
movq_cfi rbx, 5*8
movq_cfi rbp, 4*8
movq_cfi r12, 3*8
movq_cfi r13, 2*8
movq_cfi r14, 1*8
movq_cfi r15, 0*8
movq_cfi_restore 0*8, r15
movq_cfi_restore 1*8, r14
movq_cfi_restore 2*8, r13
movq_cfi_restore 3*8, r12
movq_cfi_restore 4*8, rbp
movq_cfi_restore 5*8, rbx
addq $REST_SKIP, %rsp
.macro SAVE_ALL
.macro RESTORE_ALL addskip=0
RESTORE_ARGS 1, \addskip
.macro icebp
.byte 0xf1