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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_OBJTOOL_H
3#define _LINUX_OBJTOOL_H
4
5#ifndef __ASSEMBLY__
6
7#include <linux/types.h>
8
9/*
10 * This struct is used by asm and inline asm code to manually annotate the
11 * location of registers on the stack.
12 */
13struct unwind_hint {
14 u32 ip;
15 s16 sp_offset;
16 u8 sp_reg;
17 u8 type;
18 u8 end;
19};
20#endif
21
22/*
23 * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
24 * (the caller's SP right before it made the call). Used for all callable
25 * functions, i.e. all C code and all callable asm functions.
26 *
27 * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
28 * points to a fully populated pt_regs from a syscall, interrupt, or exception.
29 *
30 * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
31 * sp_reg+sp_offset points to the iret return frame.
32 *
33 * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
34 * Useful for code which doesn't have an ELF function annotation.
35 */
36#define UNWIND_HINT_TYPE_CALL 0
37#define UNWIND_HINT_TYPE_REGS 1
38#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
39#define UNWIND_HINT_TYPE_FUNC 3
40
41#ifdef CONFIG_OBJTOOL
42
43#include <asm/asm.h>
44
45#ifndef __ASSEMBLY__
46
47#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
48 "987: \n\t" \
49 ".pushsection .discard.unwind_hints\n\t" \
50 /* struct unwind_hint */ \
51 ".long 987b - .\n\t" \
52 ".short " __stringify(sp_offset) "\n\t" \
53 ".byte " __stringify(sp_reg) "\n\t" \
54 ".byte " __stringify(type) "\n\t" \
55 ".byte " __stringify(end) "\n\t" \
56 ".balign 4 \n\t" \
57 ".popsection\n\t"
58
59/*
60 * This macro marks the given function's stack frame as "non-standard", which
61 * tells objtool to ignore the function when doing stack metadata validation.
62 * It should only be used in special cases where you're 100% sure it won't
63 * affect the reliability of frame pointers and kernel stack traces.
64 *
65 * For more information, see tools/objtool/Documentation/stack-validation.txt.
66 */
67#define STACK_FRAME_NON_STANDARD(func) \
68 static void __used __section(".discard.func_stack_frame_non_standard") \
69 *__func_stack_frame_non_standard_##func = func
70
71/*
72 * STACK_FRAME_NON_STANDARD_FP() is a frame-pointer-specific function ignore
73 * for the case where a function is intentionally missing frame pointer setup,
74 * but otherwise needs objtool/ORC coverage when frame pointers are disabled.
75 */
76#ifdef CONFIG_FRAME_POINTER
77#define STACK_FRAME_NON_STANDARD_FP(func) STACK_FRAME_NON_STANDARD(func)
78#else
79#define STACK_FRAME_NON_STANDARD_FP(func)
80#endif
81
82#define ANNOTATE_NOENDBR \
83 "986: \n\t" \
84 ".pushsection .discard.noendbr\n\t" \
85 _ASM_PTR " 986b\n\t" \
86 ".popsection\n\t"
87
88#define ASM_REACHABLE \
89 "998:\n\t" \
90 ".pushsection .discard.reachable\n\t" \
91 ".long 998b - .\n\t" \
92 ".popsection\n\t"
93
94#else /* __ASSEMBLY__ */
95
96/*
97 * This macro indicates that the following intra-function call is valid.
98 * Any non-annotated intra-function call will cause objtool to issue a warning.
99 */
100#define ANNOTATE_INTRA_FUNCTION_CALL \
101 999: \
102 .pushsection .discard.intra_function_calls; \
103 .long 999b; \
104 .popsection;
105
106/*
107 * In asm, there are two kinds of code: normal C-type callable functions and
108 * the rest. The normal callable functions can be called by other code, and
109 * don't do anything unusual with the stack. Such normal callable functions
110 * are annotated with the ENTRY/ENDPROC macros. Most asm code falls in this
111 * category. In this case, no special debugging annotations are needed because
112 * objtool can automatically generate the ORC data for the ORC unwinder to read
113 * at runtime.
114 *
115 * Anything which doesn't fall into the above category, such as syscall and
116 * interrupt handlers, tends to not be called directly by other functions, and
117 * often does unusual non-C-function-type things with the stack pointer. Such
118 * code needs to be annotated such that objtool can understand it. The
119 * following CFI hint macros are for this type of code.
120 *
121 * These macros provide hints to objtool about the state of the stack at each
122 * instruction. Objtool starts from the hints and follows the code flow,
123 * making automatic CFI adjustments when it sees pushes and pops, filling out
124 * the debuginfo as necessary. It will also warn if it sees any
125 * inconsistencies.
126 */
127.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
128.Lunwind_hint_ip_\@:
129 .pushsection .discard.unwind_hints
130 /* struct unwind_hint */
131 .long .Lunwind_hint_ip_\@ - .
132 .short \sp_offset
133 .byte \sp_reg
134 .byte \type
135 .byte \end
136 .balign 4
137 .popsection
138.endm
139
140.macro STACK_FRAME_NON_STANDARD func:req
141 .pushsection .discard.func_stack_frame_non_standard, "aw"
142 _ASM_PTR \func
143 .popsection
144.endm
145
146.macro STACK_FRAME_NON_STANDARD_FP func:req
147#ifdef CONFIG_FRAME_POINTER
148 STACK_FRAME_NON_STANDARD \func
149#endif
150.endm
151
152.macro ANNOTATE_NOENDBR
153.Lhere_\@:
154 .pushsection .discard.noendbr
155 .quad .Lhere_\@
156 .popsection
157.endm
158
159.macro REACHABLE
160.Lhere_\@:
161 .pushsection .discard.reachable
162 .long .Lhere_\@ - .
163 .popsection
164.endm
165
166#endif /* __ASSEMBLY__ */
167
168#else /* !CONFIG_OBJTOOL */
169
170#ifndef __ASSEMBLY__
171
172#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
173 "\n\t"
174#define STACK_FRAME_NON_STANDARD(func)
175#define STACK_FRAME_NON_STANDARD_FP(func)
176#define ANNOTATE_NOENDBR
177#define ASM_REACHABLE
178#else
179#define ANNOTATE_INTRA_FUNCTION_CALL
180.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
181.endm
182.macro STACK_FRAME_NON_STANDARD func:req
183.endm
184.macro ANNOTATE_NOENDBR
185.endm
186.macro REACHABLE
187.endm
188#endif
189
190#endif /* CONFIG_OBJTOOL */
191
192#endif /* _LINUX_OBJTOOL_H */