1 #include <linux/jump_label.h>
2 #include <asm/unwind_hints.h>
6 x86 function call convention, 64-bit:
7 -------------------------------------
8 arguments | callee-saved | extra caller-saved | return
9 [callee-clobbered] | | [callee-clobbered] |
10 ---------------------------------------------------------------------------
11 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
13 ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
14 functions when it sees tail-call optimization possibilities) rflags is
15 clobbered. Leftover arguments are passed over the stack frame.)
17 [*] In the frame-pointers case rbp is fixed to the stack frame.
19 [**] for struct return values wider than 64 bits the return convention is a
20 bit more complex: up to 128 bits width we return small structures
21 straight in rax, rdx. For structures larger than that (3 words or
22 larger) the caller puts a pointer to an on-stack return struct
23 [allocated in the caller's stack frame] into the first argument - i.e.
24 into rdi. All other arguments shift up by one in this case.
25 Fortunately this case is rare in the kernel.
27 For 32-bit we have the following conventions - kernel is built with
28 -mregparm=3 and -freg-struct-return:
30 x86 function calling convention, 32-bit:
31 ----------------------------------------
32 arguments | callee-saved | extra caller-saved | return
33 [callee-clobbered] | | [callee-clobbered] |
34 -------------------------------------------------------------------------
35 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
37 ( here too esp is obviously invariant across normal function calls. eflags
38 is clobbered. Leftover arguments are passed over the stack frame. )
40 [*] In the frame-pointers case ebp is fixed to the stack frame.
42 [**] We build with -freg-struct-return, which on 32-bit means similar
43 semantics as on 64-bit: edx can be used for a second return value
44 (i.e. covering integer and structure sizes up to 64 bits) - after that
45 it gets more complex and more expensive: 3-word or larger struct returns
46 get done in the caller's frame and the pointer to the return struct goes
47 into regparm0, i.e. eax - the other arguments shift up and the
48 function's register parameters degenerate to regparm=2 in essence.
55 * 64-bit system call stack frame layout defines and helpers,
59 /* The layout forms the "struct pt_regs" on the stack: */
61 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
62 * unless syscall needs a complete, fully filled "struct pt_regs".
70 /* These regs are callee-clobbered. Always saved on kernel entry. */
81 * On syscall entry, this is syscall#. On CPU exception, this is error code.
82 * On hw interrupt, it's IRQ number:
85 /* Return frame for iretq */
92 #define SIZEOF_PTREGS 21*8
94 .macro ALLOC_PT_GPREGS_ON_STACK
98 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
100 movq %r11, 6*8+\offset(%rsp)
103 movq %r10, 7*8+\offset(%rsp)
104 movq %r9, 8*8+\offset(%rsp)
105 movq %r8, 9*8+\offset(%rsp)
108 movq %rax, 10*8+\offset(%rsp)
111 movq %rcx, 11*8+\offset(%rsp)
113 movq %rdx, 12*8+\offset(%rsp)
114 movq %rsi, 13*8+\offset(%rsp)
115 movq %rdi, 14*8+\offset(%rsp)
116 UNWIND_HINT_REGS offset=\offset extra=0
118 .macro SAVE_C_REGS offset=0
119 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
121 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
122 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
124 .macro SAVE_C_REGS_EXCEPT_R891011
125 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
127 .macro SAVE_C_REGS_EXCEPT_RCX_R891011
128 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
130 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
131 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
134 .macro SAVE_EXTRA_REGS offset=0
135 movq %r15, 0*8+\offset(%rsp)
136 movq %r14, 1*8+\offset(%rsp)
137 movq %r13, 2*8+\offset(%rsp)
138 movq %r12, 3*8+\offset(%rsp)
139 movq %rbp, 4*8+\offset(%rsp)
140 movq %rbx, 5*8+\offset(%rsp)
141 UNWIND_HINT_REGS offset=\offset
144 .macro POP_EXTRA_REGS
170 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The
171 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding
172 * is just setting the LSB, which makes it an invalid stack address and is also
173 * a signal to the unwinder that it's a pt_regs pointer in disguise.
175 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
178 .macro ENCODE_FRAME_POINTER ptregs_offset=0
179 #ifdef CONFIG_FRAME_POINTER
181 leaq \ptregs_offset(%rsp), %rbp
189 #endif /* CONFIG_X86_64 */
192 * This does 'call enter_from_user_mode' unless we can avoid it based on
193 * kernel config or using the static jump infrastructure.
195 .macro CALL_enter_from_user_mode
196 #ifdef CONFIG_CONTEXT_TRACKING
197 #ifdef HAVE_JUMP_LABEL
198 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
200 call enter_from_user_mode