62 lines
2.0 KiB
C
62 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __LINUX_INSTRUMENTATION_H
|
|
#define __LINUX_INSTRUMENTATION_H
|
|
|
|
#ifdef CONFIG_VMLINUX_VALIDATION
|
|
|
|
#include <linux/stringify.h>
|
|
|
|
/* Begin/end of an instrumentation safe region */
|
|
#define __instrumentation_begin(c) ({ \
|
|
asm volatile(__stringify(c) ": nop\n\t" \
|
|
".pushsection .discard.instr_begin\n\t" \
|
|
".long " __stringify(c) "b - .\n\t" \
|
|
".popsection\n\t" : : "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" \
|
|
".pushsection .discard.instr_end\n\t" \
|
|
".long " __stringify(c) "b - .\n\t" \
|
|
".popsection\n\t" : : "i" (c)); \
|
|
})
|
|
#define instrumentation_end() __instrumentation_end(__COUNTER__)
|
|
#else /* !CONFIG_VMLINUX_VALIDATION */
|
|
# define instrumentation_begin() do { } while(0)
|
|
# define instrumentation_end() do { } while(0)
|
|
#endif /* CONFIG_VMLINUX_VALIDATION */
|
|
|
|
#endif /* __LINUX_INSTRUMENTATION_H */
|