Commit 5ece0817 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull header cleanup from Ingo Molnar:
 "Separate out the instrumentation_begin()/end() bits from compiler.h"

* tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  compiler.h: Move instrumentation_begin()/end() to new <linux/instrumentation.h> header
parents c8e69391 d19e789f

arch/x86/include/asm/bug.h

+1 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#define _ASM_X86_BUG_H



#include <linux/stringify.h>

#include <linux/instrumentation.h>



/*

 * Despite that some emulators terminate on UD2, we use it for WARN().

include/asm-generic/bug.h

+1 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#define _ASM_GENERIC_BUG_H



#include <linux/compiler.h>

#include <linux/instrumentation.h>



#define CUT_HERE		"------------[ cut here ]------------\n"

include/linux/compiler.h

+0 −53
Original line number Diff line number Diff line
@@ -120,65 +120,12 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 
/* Annotate a C jump table to allow objtool to follow the code flow */

#define __annotate_jump_table __section(.rodata..c_jump_table)



#ifdef CONFIG_DEBUG_ENTRY

/* Begin/end of an instrumentation safe region */

#define instrumentation_begin() ({					\

	asm volatile("%c0: nop\n\t"						\

		     ".pushsection .discard.instr_begin\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__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() ({					\

	asm volatile("%c0: nop\n\t"					\

		     ".pushsection .discard.instr_end\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__COUNTER__));		\

})

#endif /* CONFIG_DEBUG_ENTRY */



#else

#define annotate_reachable()

#define annotate_unreachable()

#define __annotate_jump_table

#endif



#ifndef instrumentation_begin

#define instrumentation_begin()		do { } while(0)

#define instrumentation_end()		do { } while(0)

#endif



#ifndef ASM_UNREACHABLE

# define ASM_UNREACHABLE

#endif

include/linux/context_tracking.h

+2 −0
Original line number Diff line number Diff line
@@ -5,6 +5,8 @@ 
#include <linux/sched.h>

#include <linux/vtime.h>

#include <linux/context_tracking_state.h>

#include <linux/instrumentation.h>



#include <asm/ptrace.h>

include/linux/instrumentation.h

0 → 100644
+57 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef __LINUX_INSTRUMENTATION_H

#define __LINUX_INSTRUMENTATION_H



#if defined(CONFIG_DEBUG_ENTRY) && defined(CONFIG_STACK_VALIDATION)



/* Begin/end of an instrumentation safe region */

#define instrumentation_begin() ({					\

	asm volatile("%c0: nop\n\t"						\

		     ".pushsection .discard.instr_begin\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__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() ({					\

	asm volatile("%c0: nop\n\t"					\

		     ".pushsection .discard.instr_end\n\t"		\

		     ".long %c0b - .\n\t"				\

		     ".popsection\n\t" : : "i" (__COUNTER__));		\

})

#else

# define instrumentation_begin()	do { } while(0)

# define instrumentation_end()		do { } while(0)

#endif



#endif /* __LINUX_INSTRUMENTATION_H */