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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_STACK_VALIDATION
42
43#ifndef __ASSEMBLY__
44
45#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
46 "987: \n\t" \
47 ".pushsection .discard.unwind_hints\n\t" \
48 /* struct unwind_hint */ \
49 ".long 987b - .\n\t" \
50 ".short " __stringify(sp_offset) "\n\t" \
51 ".byte " __stringify(sp_reg) "\n\t" \
52 ".byte " __stringify(type) "\n\t" \
53 ".byte " __stringify(end) "\n\t" \
54 ".balign 4 \n\t" \
55 ".popsection\n\t"
56
57/*
58 * This macro marks the given function's stack frame as "non-standard", which
59 * tells objtool to ignore the function when doing stack metadata validation.
60 * It should only be used in special cases where you're 100% sure it won't
61 * affect the reliability of frame pointers and kernel stack traces.
62 *
63 * For more information, see tools/objtool/Documentation/stack-validation.txt.
64 */
65#define STACK_FRAME_NON_STANDARD(func) \
66 static void __used __section(".discard.func_stack_frame_non_standard") \
67 *__func_stack_frame_non_standard_##func = func
68
69/*
70 * STACK_FRAME_NON_STANDARD_FP() is a frame-pointer-specific function ignore
71 * for the case where a function is intentionally missing frame pointer setup,
72 * but otherwise needs objtool/ORC coverage when frame pointers are disabled.
73 */
74#ifdef CONFIG_FRAME_POINTER
75#define STACK_FRAME_NON_STANDARD_FP(func) STACK_FRAME_NON_STANDARD(func)
76#else
77#define STACK_FRAME_NON_STANDARD_FP(func)
78#endif
79
80#define ANNOTATE_NOENDBR \
81 "986: \n\t" \
82 ".pushsection .discard.noendbr\n\t" \
83 _ASM_PTR " 986b\n\t" \
84 ".popsection\n\t"
85
86#define ASM_REACHABLE \
87 "998:\n\t" \
88 ".pushsection .discard.reachable\n\t" \
89 ".long 998b - .\n\t" \
90 ".popsection\n\t"
91
92#else /* __ASSEMBLY__ */
93
94/*
95 * This macro indicates that the following intra-function call is valid.
96 * Any non-annotated intra-function call will cause objtool to issue a warning.
97 */
98#define ANNOTATE_INTRA_FUNCTION_CALL \
99 999: \
100 .pushsection .discard.intra_function_calls; \
101 .long 999b; \
102 .popsection;
103
104/*
105 * In asm, there are two kinds of code: normal C-type callable functions and
106 * the rest. The normal callable functions can be called by other code, and
107 * don't do anything unusual with the stack. Such normal callable functions
108 * are annotated with the ENTRY/ENDPROC macros. Most asm code falls in this
109 * category. In this case, no special debugging annotations are needed because
110 * objtool can automatically generate the ORC data for the ORC unwinder to read
111 * at runtime.
112 *
113 * Anything which doesn't fall into the above category, such as syscall and
114 * interrupt handlers, tends to not be called directly by other functions, and
115 * often does unusual non-C-function-type things with the stack pointer. Such
116 * code needs to be annotated such that objtool can understand it. The
117 * following CFI hint macros are for this type of code.
118 *
119 * These macros provide hints to objtool about the state of the stack at each
120 * instruction. Objtool starts from the hints and follows the code flow,
121 * making automatic CFI adjustments when it sees pushes and pops, filling out
122 * the debuginfo as necessary. It will also warn if it sees any
123 * inconsistencies.
124 */
125.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
126.Lunwind_hint_ip_\@:
127 .pushsection .discard.unwind_hints
128 /* struct unwind_hint */
129 .long .Lunwind_hint_ip_\@ - .
130 .short \sp_offset
131 .byte \sp_reg
132 .byte \type
133 .byte \end
134 .balign 4
135 .popsection
136.endm
137
138.macro STACK_FRAME_NON_STANDARD func:req
139 .pushsection .discard.func_stack_frame_non_standard, "aw"
140 .long \func - .
141 .popsection
142.endm
143
144.macro ANNOTATE_NOENDBR
145.Lhere_\@:
146 .pushsection .discard.noendbr
147 .quad .Lhere_\@
148 .popsection
149.endm
150
151.macro REACHABLE
152.Lhere_\@:
153 .pushsection .discard.reachable
154 .long .Lhere_\@ - .
155 .popsection
156.endm
157
158#endif /* __ASSEMBLY__ */
159
160#else /* !CONFIG_STACK_VALIDATION */
161
162#ifndef __ASSEMBLY__
163
164#define UNWIND_HINT(sp_reg, sp_offset, type, end) \
165 "\n\t"
166#define STACK_FRAME_NON_STANDARD(func)
167#define STACK_FRAME_NON_STANDARD_FP(func)
168#define ANNOTATE_NOENDBR
169#define ASM_REACHABLE
170#else
171#define ANNOTATE_INTRA_FUNCTION_CALL
172.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
173.endm
174.macro STACK_FRAME_NON_STANDARD func:req
175.endm
176.macro ANNOTATE_NOENDBR
177.endm
178.macro REACHABLE
179.endm
180#endif
181
182#endif /* CONFIG_STACK_VALIDATION */
183
184#endif /* _LINUX_OBJTOOL_H */