Commit c199f64f authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Josh Poimboeuf
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instrumentation.h: Avoid using inline asm operand modifiers 



The expansion of instrumentation_begin/instrumentation_end on s390 will
result in a compiler error if the __COUNTER__ value is high enough.
For example with "i" (154) the "%c0" operand of annotate_reachable
will be expanded to -102:

        -102:
        .pushsection .discard.instr_begin
        .long -102b - .
        .popsection

This is a quirk of the gcc backend for s390, it interprets the %c0
as a signed byte value. Avoid using operand modifiers in this case
by simply converting __COUNTER__ to string, with the same result,
but in an arch assembler independent way.

Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/patch-2.thread-1a26be.git-1a26be80cb18.your-ad-here.call-01621428935-ext-2104@work.hours
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: linux-kernel@vger.kernel.org
parent f1069a87

include/linux/instrumentation.h

+12 −8
Original line number Diff line number Diff line
@@ -4,13 +4,16 @@ 


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



#include <linux/stringify.h>



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

#define instrumentation_begin() ({					\

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

#define __instrumentation_begin(c) ({					\

	asm volatile(__stringify(c) ": nop\n\t"				\

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

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

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

		     ".long " __stringify(c) "b - .\n\t"		\

		     ".popsection\n\t");				\

})

#define instrumentation_begin() __instrumentation_begin(__COUNTER__)



/*

 * Because instrumentation_{begin,end}() can nest, objtool validation considers
@@ -43,12 +46,13 @@ 
 * 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"					\

#define __instrumentation_end(c) ({					\

	asm volatile(__stringify(c) ": nop\n\t"				\

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

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

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

		     ".long " __stringify(c) "b - .\n\t"		\

		     ".popsection\n\t");				\

})

#define instrumentation_end() __instrumentation_end(__COUNTER__)

#else

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

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