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57 lines
1.7 KiB
57 lines
1.7 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef __LINUX_INSTRUMENTATION_H |
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#define __LINUX_INSTRUMENTATION_H |
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#if defined(CONFIG_DEBUG_ENTRY) && defined(CONFIG_STACK_VALIDATION) |
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/* Begin/end of an instrumentation safe region */ |
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#define instrumentation_begin() ({ \ |
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asm volatile("%c0: nop\n\t" \ |
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".pushsection .discard.instr_begin\n\t" \ |
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".long %c0b - .\n\t" \ |
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".popsection\n\t" : : "i" (__COUNTER__)); \ |
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}) |
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/* |
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* Because instrumentation_{begin,end}() can nest, objtool validation considers |
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* _begin() a +1 and _end() a -1 and computes a sum over the instructions. |
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* When the value is greater than 0, we consider instrumentation allowed. |
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* |
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* There is a problem with code like: |
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* |
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* noinstr void foo() |
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* { |
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* instrumentation_begin(); |
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* ... |
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* if (cond) { |
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* instrumentation_begin(); |
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* ... |
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* instrumentation_end(); |
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* } |
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* bar(); |
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* instrumentation_end(); |
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* } |
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* |
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* If instrumentation_end() would be an empty label, like all the other |
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* annotations, the inner _end(), which is at the end of a conditional block, |
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* would land on the instruction after the block. |
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* |
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* If we then consider the sum of the !cond path, we'll see that the call to |
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* bar() is with a 0-value, even though, we meant it to happen with a positive |
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* value. |
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* |
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* To avoid this, have _end() be a NOP instruction, this ensures it will be |
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* part of the condition block and does not escape. |
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*/ |
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#define instrumentation_end() ({ \ |
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asm volatile("%c0: nop\n\t" \ |
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".pushsection .discard.instr_end\n\t" \ |
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".long %c0b - .\n\t" \ |
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".popsection\n\t" : : "i" (__COUNTER__)); \ |
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}) |
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#else |
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# define instrumentation_begin() do { } while(0) |
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# define instrumentation_end() do { } while(0) |
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#endif |
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#endif /* __LINUX_INSTRUMENTATION_H */
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