1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_FRAME_H
3 #define _ASM_X86_FRAME_H
4 
5 #include <asm/asm.h>
6 
7 /*
8  * These are stack frame creation macros.  They should be used by every
9  * callable non-leaf asm function to make kernel stack traces more reliable.
10  */
11 
12 #ifdef CONFIG_FRAME_POINTER
13 
14 #ifdef __ASSEMBLY__
15 
16 .macro FRAME_BEGIN
17 	push %_ASM_BP
18 	_ASM_MOV %_ASM_SP, %_ASM_BP
19 .endm
20 
21 .macro FRAME_END
22 	pop %_ASM_BP
23 .endm
24 
25 #ifdef CONFIG_X86_64
26 /*
27  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
28  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
29  * is just setting the LSB, which makes it an invalid stack address and is also
30  * a signal to the unwinder that it's a pt_regs pointer in disguise.
31  *
32  * NOTE: This macro must be used *after* PUSH_AND_CLEAR_REGS because it corrupts
33  * the original rbp.
34  */
35 .macro ENCODE_FRAME_POINTER ptregs_offset=0
36 	leaq 1+\ptregs_offset(%rsp), %rbp
37 .endm
38 #else /* !CONFIG_X86_64 */
39 /*
40  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
41  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
42  * is just clearing the MSB, which makes it an invalid stack address and is also
43  * a signal to the unwinder that it's a pt_regs pointer in disguise.
44  *
45  * NOTE: This macro must be used *after* SAVE_ALL because it corrupts the
46  * original ebp.
47  */
48 .macro ENCODE_FRAME_POINTER
49 	mov %esp, %ebp
50 	andl $0x7fffffff, %ebp
51 .endm
52 #endif /* CONFIG_X86_64 */
53 
54 #else /* !__ASSEMBLY__ */
55 
56 #define FRAME_BEGIN				\
57 	"push %" _ASM_BP "\n"			\
58 	_ASM_MOV "%" _ASM_SP ", %" _ASM_BP "\n"
59 
60 #define FRAME_END "pop %" _ASM_BP "\n"
61 
62 #ifdef CONFIG_X86_64
63 
64 #define ENCODE_FRAME_POINTER			\
65 	"lea 1(%rsp), %rbp\n\t"
66 
encode_frame_pointer(struct pt_regs * regs)67 static inline unsigned long encode_frame_pointer(struct pt_regs *regs)
68 {
69 	return (unsigned long)regs + 1;
70 }
71 
72 #else /* !CONFIG_X86_64 */
73 
74 #define ENCODE_FRAME_POINTER			\
75 	"movl %esp, %ebp\n\t"			\
76 	"andl $0x7fffffff, %ebp\n\t"
77 
encode_frame_pointer(struct pt_regs * regs)78 static inline unsigned long encode_frame_pointer(struct pt_regs *regs)
79 {
80 	return (unsigned long)regs & 0x7fffffff;
81 }
82 
83 #endif /* CONFIG_X86_64 */
84 
85 #endif /* __ASSEMBLY__ */
86 
87 #define FRAME_OFFSET __ASM_SEL(4, 8)
88 
89 #else /* !CONFIG_FRAME_POINTER */
90 
91 #ifdef __ASSEMBLY__
92 
93 .macro ENCODE_FRAME_POINTER ptregs_offset=0
94 .endm
95 
96 #else /* !__ASSEMBLY */
97 
98 #define ENCODE_FRAME_POINTER
99 
encode_frame_pointer(struct pt_regs * regs)100 static inline unsigned long encode_frame_pointer(struct pt_regs *regs)
101 {
102 	return 0;
103 }
104 
105 #endif
106 
107 #define FRAME_BEGIN
108 #define FRAME_END
109 #define FRAME_OFFSET 0
110 
111 #endif /* CONFIG_FRAME_POINTER */
112 
113 #endif /* _ASM_X86_FRAME_H */
114