221 lines
5.5 KiB
C
221 lines
5.5 KiB
C
/*
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x86 function call convention, 64-bit:
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-------------------------------------
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arguments | callee-saved | extra caller-saved | return
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[callee-clobbered] | | [callee-clobbered] |
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---------------------------------------------------------------------------
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rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
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( rsp is obviously invariant across normal function calls. (gcc can 'merge'
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functions when it sees tail-call optimization possibilities) rflags is
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clobbered. Leftover arguments are passed over the stack frame.)
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[*] In the frame-pointers case rbp is fixed to the stack frame.
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[**] for struct return values wider than 64 bits the return convention is a
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bit more complex: up to 128 bits width we return small structures
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straight in rax, rdx. For structures larger than that (3 words or
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larger) the caller puts a pointer to an on-stack return struct
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[allocated in the caller's stack frame] into the first argument - i.e.
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into rdi. All other arguments shift up by one in this case.
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Fortunately this case is rare in the kernel.
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For 32-bit we have the following conventions - kernel is built with
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-mregparm=3 and -freg-struct-return:
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x86 function calling convention, 32-bit:
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----------------------------------------
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arguments | callee-saved | extra caller-saved | return
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[callee-clobbered] | | [callee-clobbered] |
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-------------------------------------------------------------------------
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eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
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( here too esp is obviously invariant across normal function calls. eflags
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is clobbered. Leftover arguments are passed over the stack frame. )
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[*] In the frame-pointers case ebp is fixed to the stack frame.
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[**] We build with -freg-struct-return, which on 32-bit means similar
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semantics as on 64-bit: edx can be used for a second return value
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(i.e. covering integer and structure sizes up to 64 bits) - after that
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it gets more complex and more expensive: 3-word or larger struct returns
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get done in the caller's frame and the pointer to the return struct goes
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into regparm0, i.e. eax - the other arguments shift up and the
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function's register parameters degenerate to regparm=2 in essence.
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*/
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/*
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* 64-bit system call stack frame layout defines and helpers,
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* for assembly code:
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*/
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#define R15 0
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#define R14 8
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#define R13 16
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#define R12 24
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#define RBP 32
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#define RBX 40
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/* arguments: interrupts/non tracing syscalls only save up to here: */
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#define R11 48
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#define R10 56
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#define R9 64
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#define R8 72
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#define RAX 80
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#define RCX 88
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#define RDX 96
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#define RSI 104
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#define RDI 112
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#define ORIG_RAX 120 /* + error_code */
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/* end of arguments */
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/* cpu exception frame or undefined in case of fast syscall: */
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#define RIP 128
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#define CS 136
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#define EFLAGS 144
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#define RSP 152
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#define SS 160
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#define ARGOFFSET R11
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#define SWFRAME ORIG_RAX
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.macro SAVE_ARGS addskip=0, norcx=0, nor891011=0
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subq $9*8+\addskip, %rsp
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CFI_ADJUST_CFA_OFFSET 9*8+\addskip
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movq %rdi, 8*8(%rsp)
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CFI_REL_OFFSET rdi, 8*8
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movq %rsi, 7*8(%rsp)
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CFI_REL_OFFSET rsi, 7*8
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movq %rdx, 6*8(%rsp)
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CFI_REL_OFFSET rdx, 6*8
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.if \norcx
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.else
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movq %rcx, 5*8(%rsp)
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CFI_REL_OFFSET rcx, 5*8
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.endif
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movq %rax, 4*8(%rsp)
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CFI_REL_OFFSET rax, 4*8
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.if \nor891011
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.else
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movq %r8, 3*8(%rsp)
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CFI_REL_OFFSET r8, 3*8
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movq %r9, 2*8(%rsp)
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CFI_REL_OFFSET r9, 2*8
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movq %r10, 1*8(%rsp)
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CFI_REL_OFFSET r10, 1*8
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movq %r11, (%rsp)
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CFI_REL_OFFSET r11, 0*8
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.endif
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.endm
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#define ARG_SKIP 9*8
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.macro RESTORE_ARGS skiprax=0, addskip=0, skiprcx=0, skipr11=0, \
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skipr8910=0, skiprdx=0
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.if \skipr11
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.else
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movq (%rsp), %r11
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CFI_RESTORE r11
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.endif
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.if \skipr8910
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.else
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movq 1*8(%rsp), %r10
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CFI_RESTORE r10
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movq 2*8(%rsp), %r9
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CFI_RESTORE r9
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movq 3*8(%rsp), %r8
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CFI_RESTORE r8
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.endif
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.if \skiprax
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.else
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movq 4*8(%rsp), %rax
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CFI_RESTORE rax
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.endif
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.if \skiprcx
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.else
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movq 5*8(%rsp), %rcx
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CFI_RESTORE rcx
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.endif
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.if \skiprdx
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.else
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movq 6*8(%rsp), %rdx
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CFI_RESTORE rdx
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.endif
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movq 7*8(%rsp), %rsi
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CFI_RESTORE rsi
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movq 8*8(%rsp), %rdi
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CFI_RESTORE rdi
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.if ARG_SKIP+\addskip > 0
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addq $ARG_SKIP+\addskip, %rsp
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CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip)
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.endif
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.endm
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.macro LOAD_ARGS offset, skiprax=0
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movq \offset(%rsp), %r11
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movq \offset+8(%rsp), %r10
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movq \offset+16(%rsp), %r9
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movq \offset+24(%rsp), %r8
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movq \offset+40(%rsp), %rcx
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movq \offset+48(%rsp), %rdx
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movq \offset+56(%rsp), %rsi
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movq \offset+64(%rsp), %rdi
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.if \skiprax
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.else
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movq \offset+72(%rsp), %rax
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.endif
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.endm
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#define REST_SKIP 6*8
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.macro SAVE_REST
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subq $REST_SKIP, %rsp
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CFI_ADJUST_CFA_OFFSET REST_SKIP
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movq %rbx, 5*8(%rsp)
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CFI_REL_OFFSET rbx, 5*8
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movq %rbp, 4*8(%rsp)
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CFI_REL_OFFSET rbp, 4*8
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movq %r12, 3*8(%rsp)
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CFI_REL_OFFSET r12, 3*8
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movq %r13, 2*8(%rsp)
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CFI_REL_OFFSET r13, 2*8
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movq %r14, 1*8(%rsp)
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CFI_REL_OFFSET r14, 1*8
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movq %r15, (%rsp)
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CFI_REL_OFFSET r15, 0*8
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.endm
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.macro RESTORE_REST
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movq (%rsp), %r15
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CFI_RESTORE r15
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movq 1*8(%rsp), %r14
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CFI_RESTORE r14
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movq 2*8(%rsp), %r13
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CFI_RESTORE r13
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movq 3*8(%rsp), %r12
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CFI_RESTORE r12
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movq 4*8(%rsp), %rbp
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CFI_RESTORE rbp
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movq 5*8(%rsp), %rbx
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CFI_RESTORE rbx
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addq $REST_SKIP, %rsp
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CFI_ADJUST_CFA_OFFSET -(REST_SKIP)
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.endm
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.macro SAVE_ALL
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SAVE_ARGS
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SAVE_REST
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.endm
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.macro RESTORE_ALL addskip=0
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RESTORE_REST
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RESTORE_ARGS 0, \addskip
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.endm
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.macro icebp
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.byte 0xf1
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.endm
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