[PATCH] debug: fix WARN_ON_ONCE() for modules

From: Josh Poimboeuf
Date: Sat Jul 15 2017 - 01:11:59 EST

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Mike Galbraith reported a situation where a WARN_ON_ONCE() call in DRM
code turned into an oops. As it turns out, WARN_ON_ONCE() seems to be
completely broken when called from a module.

The bug was introduced with the following commit:

19d436268dde ("debug: Add _ONCE() logic to report_bug()")

That commit changed WARN_ON_ONCE() to move its 'once' logic into the bug
trap handler. It requires a writable bug table so that the BUGFLAG_DONE
bit can be written to the flags to indicate the first warning has
occurred.

The bug table was made writable for vmlinux, which relies on
vmlinux.lds.S and vmlinux.lds.h for laying out the sections. However,
it wasn't made writable for modules, which rely on the ELF section
header flags.

Reported-by: Mike Galbraith <efault@xxxxxx>
Fixes: 19d436268dde ("debug: Add _ONCE() logic to report_bug()")
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
arch/arm/include/asm/bug.h | 2 +-
arch/arm64/include/asm/bug.h | 2 +-
arch/blackfin/include/asm/bug.h | 4 ++--
arch/mn10300/include/asm/bug.h | 2 +-
arch/parisc/include/asm/bug.h | 6 +++---
arch/powerpc/include/asm/bug.h | 8 ++++----
arch/s390/include/asm/bug.h | 4 ++--
arch/sh/include/asm/bug.h | 4 ++--
arch/x86/include/asm/bug.h | 4 ++--
9 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
index 4e6e88a..2244a94e 100644
--- a/arch/arm/include/asm/bug.h
+++ b/arch/arm/include/asm/bug.h
@@ -37,7 +37,7 @@ do { \
".pushsection .rodata.str, \"aMS\", %progbits, 1\n" \
"2:\t.asciz " #__file "\n" \
".popsection\n" \
- ".pushsection __bug_table,\"a\"\n" \
+ ".pushsection __bug_table,\"aw\"\n" \
".align 2\n" \
"3:\t.word 1b, 2b\n" \
"\t.hword " #__line ", 0\n" \
diff --git a/arch/arm64/include/asm/bug.h b/arch/arm64/include/asm/bug.h
index 366448e..a02a571 100644
--- a/arch/arm64/include/asm/bug.h
+++ b/arch/arm64/include/asm/bug.h
@@ -36,7 +36,7 @@
#ifdef CONFIG_GENERIC_BUG

#define __BUG_ENTRY(flags) \
- ".pushsection __bug_table,\"a\"\n\t" \
+ ".pushsection __bug_table,\"aw\"\n\t" \
".align 2\n\t" \
"0: .long 1f - 0b\n\t" \
_BUGVERBOSE_LOCATION(__FILE__, __LINE__) \
diff --git a/arch/blackfin/include/asm/bug.h b/arch/blackfin/include/asm/bug.h
index 8d9b1eb..76b2e82 100644
--- a/arch/blackfin/include/asm/bug.h
+++ b/arch/blackfin/include/asm/bug.h
@@ -21,7 +21,7 @@
#define _BUG_OR_WARN(flags) \
asm volatile( \
"1: .hword %0\n" \
- " .section __bug_table,\"a\",@progbits\n" \
+ " .section __bug_table,\"aw\",@progbits\n" \
"2: .long 1b\n" \
" .long %1\n" \
" .short %2\n" \
@@ -38,7 +38,7 @@
#define _BUG_OR_WARN(flags) \
asm volatile( \
"1: .hword %0\n" \
- " .section __bug_table,\"a\",@progbits\n" \
+ " .section __bug_table,\"aw\",@progbits\n" \
"2: .long 1b\n" \
" .short %1\n" \
" .org 2b + %2\n" \
diff --git a/arch/mn10300/include/asm/bug.h b/arch/mn10300/include/asm/bug.h
index aa6a388..811414f 100644
--- a/arch/mn10300/include/asm/bug.h
+++ b/arch/mn10300/include/asm/bug.h
@@ -21,7 +21,7 @@ do { \
asm volatile( \
" syscall 15 \n" \
"0: \n" \
- " .section __bug_table,\"a\" \n" \
+ " .section __bug_table,\"aw\" \n" \
" .long 0b,%0,%1 \n" \
" .previous \n" \
: \
diff --git a/arch/parisc/include/asm/bug.h b/arch/parisc/include/asm/bug.h
index d274227..07ea467 100644
--- a/arch/parisc/include/asm/bug.h
+++ b/arch/parisc/include/asm/bug.h
@@ -27,7 +27,7 @@
do { \
asm volatile("\n" \
"1:\t" PARISC_BUG_BREAK_ASM "\n" \
- "\t.pushsection __bug_table,\"a\"\n" \
+ "\t.pushsection __bug_table,\"aw\"\n" \
"2:\t" ASM_WORD_INSN "1b, %c0\n" \
"\t.short %c1, %c2\n" \
"\t.org 2b+%c3\n" \
@@ -50,7 +50,7 @@
do { \
asm volatile("\n" \
"1:\t" PARISC_BUG_BREAK_ASM "\n" \
- "\t.pushsection __bug_table,\"a\"\n" \
+ "\t.pushsection __bug_table,\"aw\"\n" \
"2:\t" ASM_WORD_INSN "1b, %c0\n" \
"\t.short %c1, %c2\n" \
"\t.org 2b+%c3\n" \
@@ -64,7 +64,7 @@
do { \
asm volatile("\n" \
"1:\t" PARISC_BUG_BREAK_ASM "\n" \
- "\t.pushsection __bug_table,\"a\"\n" \
+ "\t.pushsection __bug_table,\"aw\"\n" \
"2:\t" ASM_WORD_INSN "1b\n" \
"\t.short %c0\n" \
"\t.org 2b+%c1\n" \
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 0151af6..87fcc19 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -18,7 +18,7 @@
#include <asm/asm-offsets.h>
#ifdef CONFIG_DEBUG_BUGVERBOSE
.macro EMIT_BUG_ENTRY addr,file,line,flags
- .section __bug_table,"a"
+ .section __bug_table,"aw"
5001: PPC_LONG \addr, 5002f
.short \line, \flags
.org 5001b+BUG_ENTRY_SIZE
@@ -29,7 +29,7 @@
.endm
#else
.macro EMIT_BUG_ENTRY addr,file,line,flags
- .section __bug_table,"a"
+ .section __bug_table,"aw"
5001: PPC_LONG \addr
.short \flags
.org 5001b+BUG_ENTRY_SIZE
@@ -42,14 +42,14 @@
sizeof(struct bug_entry), respectively */
#ifdef CONFIG_DEBUG_BUGVERBOSE
#define _EMIT_BUG_ENTRY \
- ".section __bug_table,\"a\"\n" \
+ ".section __bug_table,\"aw\"\n" \
"2:\t" PPC_LONG "1b, %0\n" \
"\t.short %1, %2\n" \
".org 2b+%3\n" \
".previous\n"
#else
#define _EMIT_BUG_ENTRY \
- ".section __bug_table,\"a\"\n" \
+ ".section __bug_table,\"aw\"\n" \
"2:\t" PPC_LONG "1b\n" \
"\t.short %2\n" \
".org 2b+%3\n" \
diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index 1bbd9db..ce9cc12 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -14,7 +14,7 @@
".section .rodata.str,\"aMS\",@progbits,1\n" \
"2: .asciz \""__FILE__"\"\n" \
".previous\n" \
- ".section __bug_table,\"a\"\n" \
+ ".section __bug_table,\"aw\"\n" \
"3: .long 1b-3b,2b-3b\n" \
" .short %0,%1\n" \
" .org 3b+%2\n" \
@@ -30,7 +30,7 @@
asm volatile( \
"0: j 0b+2\n" \
"1:\n" \
- ".section __bug_table,\"a\"\n" \
+ ".section __bug_table,\"aw\"\n" \
"2: .long 1b-2b\n" \
" .short %0\n" \
" .org 2b+%1\n" \
diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
index 1b77f06..986c878 100644
--- a/arch/sh/include/asm/bug.h
+++ b/arch/sh/include/asm/bug.h
@@ -24,14 +24,14 @@
*/
#ifdef CONFIG_DEBUG_BUGVERBOSE
#define _EMIT_BUG_ENTRY \
- "\t.pushsection __bug_table,\"a\"\n" \
+ "\t.pushsection __bug_table,\"aw\"\n" \
"2:\t.long 1b, %O1\n" \
"\t.short %O2, %O3\n" \
"\t.org 2b+%O4\n" \
"\t.popsection\n"
#else
#define _EMIT_BUG_ENTRY \
- "\t.pushsection __bug_table,\"a\"\n" \
+ "\t.pushsection __bug_table,\"aw\"\n" \
"2:\t.long 1b\n" \
"\t.short %O3\n" \
"\t.org 2b+%O4\n" \
diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index 39e702d..aa6b202 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -35,7 +35,7 @@
#define _BUG_FLAGS(ins, flags) \
do { \
asm volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"a\"\n" \
+ ".pushsection __bug_table,\"aw\"\n" \
"2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
"\t" __BUG_REL(%c0) "\t# bug_entry::file\n" \
"\t.word %c1" "\t# bug_entry::line\n" \
@@ -52,7 +52,7 @@ do { \
#define _BUG_FLAGS(ins, flags) \
do { \
asm volatile("1:\t" ins "\n" \
- ".pushsection __bug_table,\"a\"\n" \
+ ".pushsection __bug_table,\"aw\"\n" \
"2:\t" __BUG_REL(1b) "\t# bug_entry::bug_addr\n" \
"\t.word %c0" "\t# bug_entry::flags\n" \
"\t.org 2b+%c1\n" \
--
2.7.5

Next message: Dominik Brodowski: "Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching""
Previous message: Fabio M. Di Nitto: "Re: [PATCH 0/2] Avoid crashes by early (boot) consoles using init memory"
Next in thread: Mike Galbraith: "Re: [PATCH] debug: fix WARN_ON_ONCE() for modules"
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