/* 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 [*] | | 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. */ #ifdef CONFIG_X86_64 /* * 64-bit system call stack frame layout defines and helpers, * for assembly code: */ /* The layout forms the "struct pt_regs" on the stack: */ /* * C ABI says these regs are callee-preserved. They aren't saved on kernel entry * unless syscall needs a complete, fully filled "struct pt_regs". */ #define R15 0*8 #define R14 1*8 #define R13 2*8 #define R12 3*8 #define RBP 4*8 #define RBX 5*8 /* These regs are callee-clobbered. Always saved on kernel entry. */ #define R11 6*8 #define R10 7*8 #define R9 8*8 #define R8 9*8 #define RAX 10*8 #define RCX 11*8 #define RDX 12*8 #define RSI 13*8 #define RDI 14*8 /* * On syscall entry, this is syscall#. On CPU exception, this is error code. * On hw interrupt, it's IRQ number: */ #define ORIG_RAX 15*8 /* Return frame for iretq */ #define RIP 16*8 #define CS 17*8 #define EFLAGS 18*8 #define RSP 19*8 #define SS 20*8 #define SIZEOF_PTREGS 21*8 .macro ALLOC_PT_GPREGS_ON_STACK addskip=0 addq $-(15*8+\addskip), %rsp .endm .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1 .if \r11 movq %r11, 6*8+\offset(%rsp) .endif .if \r8910 movq %r10, 7*8+\offset(%rsp) movq %r9, 8*8+\offset(%rsp) movq %r8, 9*8+\offset(%rsp) .endif .if \rax movq %rax, 10*8+\offset(%rsp) .endif .if \rcx movq %rcx, 11*8+\offset(%rsp) .endif movq %rdx, 12*8+\offset(%rsp) movq %rsi, 13*8+\offset(%rsp) movq %rdi, 14*8+\offset(%rsp) .endm .macro SAVE_C_REGS offset=0 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1 .endm .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1 .endm .macro SAVE_C_REGS_EXCEPT_R891011 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0 .endm .macro SAVE_C_REGS_EXCEPT_RCX_R891011 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0 .endm .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0 .endm .macro SAVE_EXTRA_REGS offset=0 movq %r15, 0*8+\offset(%rsp) movq %r14, 1*8+\offset(%rsp) movq %r13, 2*8+\offset(%rsp) movq %r12, 3*8+\offset(%rsp) movq %rbp, 4*8+\offset(%rsp) movq %rbx, 5*8+\offset(%rsp) .endm .macro RESTORE_EXTRA_REGS offset=0 movq 0*8+\offset(%rsp), %r15 movq 1*8+\offset(%rsp), %r14 movq 2*8+\offset(%rsp), %r13 movq 3*8+\offset(%rsp), %r12 movq 4*8+\offset(%rsp), %rbp movq 5*8+\offset(%rsp), %rbx .endm .macro ZERO_EXTRA_REGS xorl %r15d, %r15d xorl %r14d, %r14d xorl %r13d, %r13d xorl %r12d, %r12d xorl %ebp, %ebp xorl %ebx, %ebx .endm .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1 .if \rstor_r11 movq 6*8(%rsp), %r11 .endif .if \rstor_r8910 movq 7*8(%rsp), %r10 movq 8*8(%rsp), %r9 movq 9*8(%rsp), %r8 .endif .if \rstor_rax movq 10*8(%rsp), %rax .endif .if \rstor_rcx movq 11*8(%rsp), %rcx .endif .if \rstor_rdx movq 12*8(%rsp), %rdx .endif movq 13*8(%rsp), %rsi movq 14*8(%rsp), %rdi .endm .macro RESTORE_C_REGS RESTORE_C_REGS_HELPER 1,1,1,1,1 .endm .macro RESTORE_C_REGS_EXCEPT_RAX RESTORE_C_REGS_HELPER 0,1,1,1,1 .endm .macro RESTORE_C_REGS_EXCEPT_RCX RESTORE_C_REGS_HELPER 1,0,1,1,1 .endm .macro RESTORE_C_REGS_EXCEPT_R11 RESTORE_C_REGS_HELPER 1,1,0,1,1 .endm .macro RESTORE_C_REGS_EXCEPT_RCX_R11 RESTORE_C_REGS_HELPER 1,0,0,1,1 .endm .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0 subq $-(15*8+\addskip), %rsp .endm .macro icebp .byte 0xf1 .endm #else /* CONFIG_X86_64 */ /* * For 32bit only simplified versions of SAVE_ALL/RESTORE_ALL. These * are different from the entry_32.S versions in not changing the segment * registers. So only suitable for in kernel use, not when transitioning * from or to user space. The resulting stack frame is not a standard * pt_regs frame. The main use case is calling C code from assembler * when all the registers need to be preserved. */ .macro SAVE_ALL pushl %eax pushl %ebp pushl %edi pushl %esi pushl %edx pushl %ecx pushl %ebx .endm .macro RESTORE_ALL popl %ebx popl %ecx popl %edx popl %esi popl %edi popl %ebp popl %eax .endm #endif /* CONFIG_X86_64 */