/* 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. */ #include #ifdef CONFIG_X86_64 /* * 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 #define SWFRAME ORIG_RAX .macro SAVE_ARGS addskip=0, save_rcx=1, save_r891011=1, rax_enosys=0 subq $9*8+\addskip, %rsp CFI_ADJUST_CFA_OFFSET 9*8+\addskip movq_cfi rdi, 8*8 movq_cfi rsi, 7*8 movq_cfi rdx, 6*8 .if \save_rcx movq_cfi rcx, 5*8 .endif .if \rax_enosys movq $-ENOSYS, 4*8(%rsp) .else movq_cfi rax, 4*8 .endif .if \save_r891011 movq_cfi r8, 3*8 movq_cfi r9, 2*8 movq_cfi r10, 1*8 movq_cfi r11, 0*8 .endif .endm #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 .endif .if \rstor_r8910 movq_cfi_restore 1*8, r10 movq_cfi_restore 2*8, r9 movq_cfi_restore 3*8, r8 .endif .if \rstor_rax movq_cfi_restore 4*8, rax .endif .if \rstor_rcx movq_cfi_restore 5*8, rcx .endif .if \rstor_rdx movq_cfi_restore 6*8, rdx .endif movq_cfi_restore 7*8, rsi movq_cfi_restore 8*8, rdi .if ARG_SKIP+\addskip > 0 addq $ARG_SKIP+\addskip, %rsp CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip) .endif .endm .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 .else movq \offset+72(%rsp), %rax .endif .endm #define REST_SKIP (6*8) .macro SAVE_REST subq $REST_SKIP, %rsp CFI_ADJUST_CFA_OFFSET REST_SKIP 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 .endm .macro RESTORE_REST 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 CFI_ADJUST_CFA_OFFSET -(REST_SKIP) .endm .macro SAVE_ALL SAVE_ARGS SAVE_REST .endm .macro RESTORE_ALL addskip=0 RESTORE_REST RESTORE_ARGS 1, \addskip .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_cfi %eax CFI_REL_OFFSET eax, 0 pushl_cfi %ebp CFI_REL_OFFSET ebp, 0 pushl_cfi %edi CFI_REL_OFFSET edi, 0 pushl_cfi %esi CFI_REL_OFFSET esi, 0 pushl_cfi %edx CFI_REL_OFFSET edx, 0 pushl_cfi %ecx CFI_REL_OFFSET ecx, 0 pushl_cfi %ebx CFI_REL_OFFSET ebx, 0 .endm .macro RESTORE_ALL popl_cfi %ebx CFI_RESTORE ebx popl_cfi %ecx CFI_RESTORE ecx popl_cfi %edx CFI_RESTORE edx popl_cfi %esi CFI_RESTORE esi popl_cfi %edi CFI_RESTORE edi popl_cfi %ebp CFI_RESTORE ebp popl_cfi %eax CFI_RESTORE eax .endm #endif /* CONFIG_X86_64 */