1 /* SPDX-License-Identifier: GPL-2.0 */
2 #include <linux/jump_label.h>
3 #include <asm/unwind_hints.h>
7 x86 function call convention, 64-bit:
8 -------------------------------------
9 arguments | callee-saved | extra caller-saved | return
10 [callee-clobbered] | | [callee-clobbered] |
11 ---------------------------------------------------------------------------
12 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
14 ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
15 functions when it sees tail-call optimization possibilities) rflags is
16 clobbered. Leftover arguments are passed over the stack frame.)
18 [*] In the frame-pointers case rbp is fixed to the stack frame.
20 [**] for struct return values wider than 64 bits the return convention is a
21 bit more complex: up to 128 bits width we return small structures
22 straight in rax, rdx. For structures larger than that (3 words or
23 larger) the caller puts a pointer to an on-stack return struct
24 [allocated in the caller's stack frame] into the first argument - i.e.
25 into rdi. All other arguments shift up by one in this case.
26 Fortunately this case is rare in the kernel.
28 For 32-bit we have the following conventions - kernel is built with
29 -mregparm=3 and -freg-struct-return:
31 x86 function calling convention, 32-bit:
32 ----------------------------------------
33 arguments | callee-saved | extra caller-saved | return
34 [callee-clobbered] | | [callee-clobbered] |
35 -------------------------------------------------------------------------
36 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
38 ( here too esp is obviously invariant across normal function calls. eflags
39 is clobbered. Leftover arguments are passed over the stack frame. )
41 [*] In the frame-pointers case ebp is fixed to the stack frame.
43 [**] We build with -freg-struct-return, which on 32-bit means similar
44 semantics as on 64-bit: edx can be used for a second return value
45 (i.e. covering integer and structure sizes up to 64 bits) - after that
46 it gets more complex and more expensive: 3-word or larger struct returns
47 get done in the caller's frame and the pointer to the return struct goes
48 into regparm0, i.e. eax - the other arguments shift up and the
49 function's register parameters degenerate to regparm=2 in essence.
56 * 64-bit system call stack frame layout defines and helpers,
60 /* The layout forms the "struct pt_regs" on the stack: */
62 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
63 * unless syscall needs a complete, fully filled "struct pt_regs".
71 /* These regs are callee-clobbered. Always saved on kernel entry. */
82 * On syscall entry, this is syscall#. On CPU exception, this is error code.
83 * On hw interrupt, it's IRQ number:
86 /* Return frame for iretq */
93 #define SIZEOF_PTREGS 21*8
95 .macro ALLOC_PT_GPREGS_ON_STACK
99 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
101 movq %r11, 6*8+\offset(%rsp)
104 movq %r10, 7*8+\offset(%rsp)
105 movq %r9, 8*8+\offset(%rsp)
106 movq %r8, 9*8+\offset(%rsp)
109 movq %rax, 10*8+\offset(%rsp)
112 movq %rcx, 11*8+\offset(%rsp)
114 movq %rdx, 12*8+\offset(%rsp)
115 movq %rsi, 13*8+\offset(%rsp)
116 movq %rdi, 14*8+\offset(%rsp)
117 UNWIND_HINT_REGS offset=\offset extra=0
119 .macro SAVE_C_REGS offset=0
120 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
122 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
123 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
125 .macro SAVE_C_REGS_EXCEPT_R891011
126 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
128 .macro SAVE_C_REGS_EXCEPT_RCX_R891011
129 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
131 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
132 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
135 .macro SAVE_EXTRA_REGS offset=0
136 movq %r15, 0*8+\offset(%rsp)
137 movq %r14, 1*8+\offset(%rsp)
138 movq %r13, 2*8+\offset(%rsp)
139 movq %r12, 3*8+\offset(%rsp)
140 movq %rbp, 4*8+\offset(%rsp)
141 movq %rbx, 5*8+\offset(%rsp)
142 UNWIND_HINT_REGS offset=\offset
145 .macro POP_EXTRA_REGS
171 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The
172 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding
173 * is just setting the LSB, which makes it an invalid stack address and is also
174 * a signal to the unwinder that it's a pt_regs pointer in disguise.
176 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
179 .macro ENCODE_FRAME_POINTER ptregs_offset=0
180 #ifdef CONFIG_FRAME_POINTER
182 leaq \ptregs_offset(%rsp), %rbp
190 #endif /* CONFIG_X86_64 */
193 * This does 'call enter_from_user_mode' unless we can avoid it based on
194 * kernel config or using the static jump infrastructure.
196 .macro CALL_enter_from_user_mode
197 #ifdef CONFIG_CONTEXT_TRACKING
198 #ifdef HAVE_JUMP_LABEL
199 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
201 call enter_from_user_mode