[tip: objtool/core] instrumentation.h: Avoid using inline asm operand modifiers

[tip-bot2 for Vasily Gorbik]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     c199f64ff93c48a45add92eee4456ffcabfc838e
Gitweb:        https://git.kernel.org/tip/c199f64ff93c48a45add92eee4456ffcabfc838e
Author:        Vasily Gorbik <gor@xxxxxxxxxxxxx>
AuthorDate:    Wed, 19 May 2021 15:03:13 +02:00
Committer:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Wed, 19 May 2021 15:30:59 -05:00

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: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Miroslav Benes <mbenes@xxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 include/linux/instrumentation.h | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/linux/instrumentation.h b/include/linux/instrumentation.h
index 93e2ad6..fa2cd8c 100644
--- a/include/linux/instrumentation.h
+++ b/include/linux/instrumentation.h
@@ -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)