lkml.org 
[lkml]   [2021]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 2/2] 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@linux.ibm.com>
---
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 93e2ad67fc10..fa2cd8c63dcc 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)
--
2.25.4
\
 
 \ /
  Last update: 2021-05-19 15:03    [W:0.128 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site