Quelle instrumentation.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_INSTRUMENTATION_H
#define __LINUX_INSTRUMENTATION_H

#ifdef CONFIG_NOINSTR_VALIDATION

#include <linux/objtool.h>
#include <linux/stringify.h>

/* Begin/end of an instrumentation safe region */
#define __instrumentation_begin(c) ({     \
asm volatile(__stringify(c) ": nop\n\t"    \
       ANNOTATE_INSTR_BEGIN(__ASM_BREF(c))  \
       : : "i" (c));     \
})
#define instrumentation_begin() __instrumentation_begin(__COUNTER__)

/*
* Because instrumentation_{begin,end}() can nest, objtool validation considers
* _begin() a +1 and _end() a -1 and computes a sum over the instructions.
* When the value is greater than 0, we consider instrumentation allowed.
*
* There is a problem with code like:
*
* noinstr void foo()
* {
* instrumentation_begin();
* ...
* if (cond) {
* instrumentation_begin();
* ...
* instrumentation_end();
* }
* bar();
* instrumentation_end();
* }
*
* If instrumentation_end() would be an empty label, like all the other
* annotations, the inner _end(), which is at the end of a conditional block,
* would land on the instruction after the block.
*
* If we then consider the sum of the !cond path, we'll see that the call to
* bar() is with a 0-value, even though, we meant it to happen with a positive
* value.
*
* To avoid this, have _end() be a NOP instruction, this ensures it will be
* part of the condition block and does not escape.
*/
#define __instrumentation_end(c) ({     \
asm volatile(__stringify(c) ": nop\n\t"    \
       ANNOTATE_INSTR_END(__ASM_BREF(c))   \
       : : "i" (c));     \
})
#define instrumentation_end() __instrumentation_end(__COUNTER__)
#else /* !CONFIG_NOINSTR_VALIDATION */
# define instrumentation_begin() do { } while(0)
# define instrumentation_end()  do { } while(0)
#endif /* CONFIG_NOINSTR_VALIDATION */

#endif /* __LINUX_INSTRUMENTATION_H */

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