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 RESTORE_EXTRA_REGS offset
=0
146 movq
0*8+\
offset(%rsp
), %r15
147 movq
1*8+\
offset(%rsp
), %r14
148 movq
2*8+\
offset(%rsp
), %r13
149 movq
3*8+\
offset(%rsp
), %r12
150 movq
4*8+\
offset(%rsp
), %rbp
151 movq
5*8+\
offset(%rsp
), %rbx
152 UNWIND_HINT_REGS offset
=\offset extra
=0
155 .macro RESTORE_C_REGS_HELPER rstor_rax
=1, rstor_rcx
=1, rstor_r11
=1, rstor_r8910
=1, rstor_rdx
=1
165 movq
10*8(%rsp
), %rax
168 movq
11*8(%rsp
), %rcx
171 movq
12*8(%rsp
), %rdx
173 movq
13*8(%rsp
), %rsi
174 movq
14*8(%rsp
), %rdi
175 UNWIND_HINT_IRET_REGS offset
=16*8
177 .macro RESTORE_C_REGS
178 RESTORE_C_REGS_HELPER
1,1,1,1,1
180 .macro RESTORE_C_REGS_EXCEPT_RAX
181 RESTORE_C_REGS_HELPER
0,1,1,1,1
183 .macro RESTORE_C_REGS_EXCEPT_RCX
184 RESTORE_C_REGS_HELPER
1,0,1,1,1
186 .macro RESTORE_C_REGS_EXCEPT_R11
187 RESTORE_C_REGS_HELPER
1,1,0,1,1
189 .macro RESTORE_C_REGS_EXCEPT_RCX_R11
190 RESTORE_C_REGS_HELPER
1,0,0,1,1
193 .macro REMOVE_PT_GPREGS_FROM_STACK addskip
=0
194 subq $
-(15*8+\addskip
), %rsp
202 * This is a sneaky trick to help the unwinder find pt_regs on the stack. The
203 * frame pointer is replaced with an encoded pointer to pt_regs. The encoding
204 * is just setting the LSB, which makes it an invalid stack address and is also
205 * a signal to the unwinder that it's a pt_regs pointer in disguise.
207 * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
210 .macro ENCODE_FRAME_POINTER ptregs_offset
=0
211 #ifdef CONFIG_FRAME_POINTER
213 leaq \
ptregs_offset(%rsp
), %rbp
221 #endif /* CONFIG_X86_64 */
224 * This does 'call enter_from_user_mode' unless we can avoid it based on
225 * kernel config or using the static jump infrastructure.
227 .macro CALL_enter_from_user_mode
228 #ifdef CONFIG_CONTEXT_TRACKING
229 #ifdef HAVE_JUMP_LABEL
230 STATIC_JUMP_IF_FALSE
.Lafter_call_\@
, context_tracking_enabled
, def
=0
232 call enter_from_user_mode