244 lines
6.4 KiB
C
244 lines
6.4 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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#ifdef CONFIG_X86_64
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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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/* The layout forms the "struct pt_regs" on the stack: */
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/*
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* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
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* unless syscall needs a complete, fully filled "struct pt_regs".
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*/
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#define R15 0*8
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#define R14 1*8
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#define R13 2*8
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#define R12 3*8
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#define RBP 4*8
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#define RBX 5*8
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/* These regs are callee-clobbered. Always saved on kernel entry. */
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#define R11 6*8
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#define R10 7*8
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#define R9 8*8
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#define R8 9*8
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#define RAX 10*8
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#define RCX 11*8
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#define RDX 12*8
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#define RSI 13*8
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#define RDI 14*8
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/*
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* On syscall entry, this is syscall#. On CPU exception, this is error code.
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* On hw interrupt, it's IRQ number:
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*/
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#define ORIG_RAX 15*8
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/* Return frame for iretq */
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#define RIP 16*8
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#define CS 17*8
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#define EFLAGS 18*8
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#define RSP 19*8
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#define SS 20*8
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#define SIZEOF_PTREGS 21*8
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.macro ALLOC_PT_GPREGS_ON_STACK addskip=0
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addq $-(15*8+\addskip), %rsp
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.endm
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.macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
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.if \r11
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movq %r11, 6*8+\offset(%rsp)
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.endif
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.if \r8910
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movq %r10, 7*8+\offset(%rsp)
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movq %r9, 8*8+\offset(%rsp)
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movq %r8, 9*8+\offset(%rsp)
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.endif
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.if \rax
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movq %rax, 10*8+\offset(%rsp)
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.endif
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.if \rcx
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movq %rcx, 11*8+\offset(%rsp)
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.endif
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movq %rdx, 12*8+\offset(%rsp)
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movq %rsi, 13*8+\offset(%rsp)
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movq %rdi, 14*8+\offset(%rsp)
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.endm
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.macro SAVE_C_REGS offset=0
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SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
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.endm
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.macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
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SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
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.endm
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.macro SAVE_C_REGS_EXCEPT_R891011
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SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
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.endm
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.macro SAVE_C_REGS_EXCEPT_RCX_R891011
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SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
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.endm
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.macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
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SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
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.endm
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.macro SAVE_EXTRA_REGS offset=0
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movq %r15, 0*8+\offset(%rsp)
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movq %r14, 1*8+\offset(%rsp)
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movq %r13, 2*8+\offset(%rsp)
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movq %r12, 3*8+\offset(%rsp)
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movq %rbp, 4*8+\offset(%rsp)
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movq %rbx, 5*8+\offset(%rsp)
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.endm
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.macro SAVE_EXTRA_REGS_RBP offset=0
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movq %rbp, 4*8+\offset(%rsp)
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.endm
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.macro RESTORE_EXTRA_REGS offset=0
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movq 0*8+\offset(%rsp), %r15
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movq 1*8+\offset(%rsp), %r14
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movq 2*8+\offset(%rsp), %r13
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movq 3*8+\offset(%rsp), %r12
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movq 4*8+\offset(%rsp), %rbp
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movq 5*8+\offset(%rsp), %rbx
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.endm
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.macro ZERO_EXTRA_REGS
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xorl %r15d, %r15d
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xorl %r14d, %r14d
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xorl %r13d, %r13d
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xorl %r12d, %r12d
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xorl %ebp, %ebp
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xorl %ebx, %ebx
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.endm
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.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
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.if \rstor_r11
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movq 6*8(%rsp), %r11
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.endif
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.if \rstor_r8910
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movq 7*8(%rsp), %r10
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movq 8*8(%rsp), %r9
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movq 9*8(%rsp), %r8
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.endif
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.if \rstor_rax
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movq 10*8(%rsp), %rax
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.endif
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.if \rstor_rcx
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movq 11*8(%rsp), %rcx
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.endif
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.if \rstor_rdx
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movq 12*8(%rsp), %rdx
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.endif
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movq 13*8(%rsp), %rsi
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movq 14*8(%rsp), %rdi
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.endm
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.macro RESTORE_C_REGS
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RESTORE_C_REGS_HELPER 1,1,1,1,1
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.endm
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.macro RESTORE_C_REGS_EXCEPT_RAX
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RESTORE_C_REGS_HELPER 0,1,1,1,1
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.endm
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.macro RESTORE_C_REGS_EXCEPT_RCX
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RESTORE_C_REGS_HELPER 1,0,1,1,1
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.endm
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.macro RESTORE_C_REGS_EXCEPT_R11
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RESTORE_C_REGS_HELPER 1,1,0,1,1
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.endm
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.macro RESTORE_C_REGS_EXCEPT_RCX_R11
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RESTORE_C_REGS_HELPER 1,0,0,1,1
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.endm
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.macro RESTORE_RSI_RDI
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RESTORE_C_REGS_HELPER 0,0,0,0,0
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.endm
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.macro RESTORE_RSI_RDI_RDX
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RESTORE_C_REGS_HELPER 0,0,0,0,1
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.endm
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.macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
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subq $-(15*8+\addskip), %rsp
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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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#else /* CONFIG_X86_64 */
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/*
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* For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These
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* are different from the entry_32.S versions in not changing the segment
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* registers. So only suitable for in kernel use, not when transitioning
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* from or to user space. The resulting stack frame is not a standard
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* pt_regs frame. The main use case is calling C code from assembler
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* when all the registers need to be preserved.
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*/
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.macro SAVE_ALL
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pushl %eax
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pushl %ebp
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pushl %edi
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pushl %esi
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pushl %edx
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pushl %ecx
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pushl %ebx
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.endm
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.macro RESTORE_ALL
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popl %ebx
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popl %ecx
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popl %edx
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popl %esi
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popl %edi
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popl %ebp
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popl %eax
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.endm
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#endif /* CONFIG_X86_64 */
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