1 /* SPDX-License-Identifier: GPL-2.0 */ 1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_INSTRUMENTATION_H 2 #ifndef __LINUX_INSTRUMENTATION_H
3 #define __LINUX_INSTRUMENTATION_H 3 #define __LINUX_INSTRUMENTATION_H
4 4
5 #ifdef CONFIG_NOINSTR_VALIDATION !! 5 #if defined(CONFIG_DEBUG_ENTRY) && defined(CONFIG_STACK_VALIDATION)
6 <<
7 #include <linux/stringify.h> <<
8 6
9 /* Begin/end of an instrumentation safe region 7 /* Begin/end of an instrumentation safe region */
10 #define __instrumentation_begin(c) ({ !! 8 #define instrumentation_begin() ({ \
11 asm volatile(__stringify(c) ": nop\n\t !! 9 asm volatile("%c0: nop\n\t" \
12 ".pushsection .discard.in 10 ".pushsection .discard.instr_begin\n\t" \
13 ".long " __stringify(c) " !! 11 ".long %c0b - .\n\t" \
14 ".popsection\n\t" : : "i" !! 12 ".popsection\n\t" : : "i" (__COUNTER__)); \
15 }) 13 })
16 #define instrumentation_begin() __instrumentat <<
17 14
18 /* 15 /*
19 * Because instrumentation_{begin,end}() can n 16 * Because instrumentation_{begin,end}() can nest, objtool validation considers
20 * _begin() a +1 and _end() a -1 and computes 17 * _begin() a +1 and _end() a -1 and computes a sum over the instructions.
21 * When the value is greater than 0, we consid 18 * When the value is greater than 0, we consider instrumentation allowed.
22 * 19 *
23 * There is a problem with code like: 20 * There is a problem with code like:
24 * 21 *
25 * noinstr void foo() 22 * noinstr void foo()
26 * { 23 * {
27 * instrumentation_begin(); 24 * instrumentation_begin();
28 * ... 25 * ...
29 * if (cond) { 26 * if (cond) {
30 * instrumentation_begin(); 27 * instrumentation_begin();
31 * ... 28 * ...
32 * instrumentation_end(); 29 * instrumentation_end();
33 * } 30 * }
34 * bar(); 31 * bar();
35 * instrumentation_end(); 32 * instrumentation_end();
36 * } 33 * }
37 * 34 *
38 * If instrumentation_end() would be an empty 35 * If instrumentation_end() would be an empty label, like all the other
39 * annotations, the inner _end(), which is at 36 * annotations, the inner _end(), which is at the end of a conditional block,
40 * would land on the instruction after the blo 37 * would land on the instruction after the block.
41 * 38 *
42 * If we then consider the sum of the !cond pa 39 * If we then consider the sum of the !cond path, we'll see that the call to
43 * bar() is with a 0-value, even though, we me 40 * bar() is with a 0-value, even though, we meant it to happen with a positive
44 * value. 41 * value.
45 * 42 *
46 * To avoid this, have _end() be a NOP instruc 43 * To avoid this, have _end() be a NOP instruction, this ensures it will be
47 * part of the condition block and does not es 44 * part of the condition block and does not escape.
48 */ 45 */
49 #define __instrumentation_end(c) ({ !! 46 #define instrumentation_end() ({ \
50 asm volatile(__stringify(c) ": nop\n\t !! 47 asm volatile("%c0: nop\n\t" \
51 ".pushsection .discard.in 48 ".pushsection .discard.instr_end\n\t" \
52 ".long " __stringify(c) " !! 49 ".long %c0b - .\n\t" \
53 ".popsection\n\t" : : "i" !! 50 ".popsection\n\t" : : "i" (__COUNTER__)); \
54 }) 51 })
55 #define instrumentation_end() __instrumentatio !! 52 #else
56 #else /* !CONFIG_NOINSTR_VALIDATION */ <<
57 # define instrumentation_begin() do { } 53 # define instrumentation_begin() do { } while(0)
58 # define instrumentation_end() do { } 54 # define instrumentation_end() do { } while(0)
59 #endif /* CONFIG_NOINSTR_VALIDATION */ !! 55 #endif
60 56
61 #endif /* __LINUX_INSTRUMENTATION_H */ 57 #endif /* __LINUX_INSTRUMENTATION_H */
62 58
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