arch/x86/entry/calling.h - arm/linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #include <linux/jump_label.h>
 #include <asm/unwind_hints.h>

 /*

  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.

 */

 #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
 	addq	$-(15*8), %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)
 	UNWIND_HINT_REGS offset=\offset extra=0
 	.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)
 	UNWIND_HINT_REGS offset=\offset
 	.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
 	UNWIND_HINT_REGS offset=\offset extra=0
 	.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
 	UNWIND_HINT_IRET_REGS offset=16*8
 	.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

 /*
  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
  * is just setting the LSB, which makes it an invalid stack address and is also
  * a signal to the unwinder that it's a pt_regs pointer in disguise.
  *
  * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
  * the original rbp.
  */
 .macro ENCODE_FRAME_POINTER ptregs_offset=0
 #ifdef CONFIG_FRAME_POINTER
 	.if \ptregs_offset
 		leaq \ptregs_offset(%rsp), %rbp
 	.else
 		mov %rsp, %rbp
 	.endif
 	orq	$0x1, %rbp
 #endif
 .endm

 #endif /* CONFIG_X86_64 */

 /*
  * This does 'call enter_from_user_mode' unless we can avoid it based on
  * kernel config or using the static jump infrastructure.
  */
 .macro CALL_enter_from_user_mode
 #ifdef CONFIG_CONTEXT_TRACKING
 #ifdef HAVE_JUMP_LABEL
 	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
 #endif
 	call enter_from_user_mode
 .Lafter_call_\@:
 #endif
 .endm
	/* SPDX-License-Identifier: GPL-2.0 */
	#include <linux/jump_label.h>
	#include <asm/unwind_hints.h>

	/*

	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.

	*/

	#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
	addq $-(15*8), %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)
	UNWIND_HINT_REGS offset=\offset extra=0
	.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)
	UNWIND_HINT_REGS offset=\offset
	.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
	UNWIND_HINT_REGS offset=\offset extra=0
	.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
	UNWIND_HINT_IRET_REGS offset=16*8
	.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

	/*
	* This is a sneaky trick to help the unwinder find pt_regs on the stack. The
	* frame pointer is replaced with an encoded pointer to pt_regs. The encoding
	* is just setting the LSB, which makes it an invalid stack address and is also
	* a signal to the unwinder that it's a pt_regs pointer in disguise.
	*
	* NOTE: This macro must be used after SAVE_EXTRA_REGS because it corrupts
	* the original rbp.
	*/
	.macro ENCODE_FRAME_POINTER ptregs_offset=0
	#ifdef CONFIG_FRAME_POINTER
	.if \ptregs_offset
	leaq \ptregs_offset(%rsp), %rbp
	.else
	mov %rsp, %rbp
	.endif
	orq $0x1, %rbp
	#endif
	.endm

	#endif /* CONFIG_X86_64 */

	/*
	* This does 'call enter_from_user_mode' unless we can avoid it based on
	* kernel config or using the static jump infrastructure.
	*/
	.macro CALL_enter_from_user_mode
	#ifdef CONFIG_CONTEXT_TRACKING
	#ifdef HAVE_JUMP_LABEL
	STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
	#endif
	call enter_from_user_mode
	.Lafter_call_\@:
	#endif
	.endm