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authorJosh Poimboeuf <jpoimboe@redhat.com>2017-07-15 08:10:58 +0300
committerIngo Molnar <mingo@kernel.org>2017-07-20 13:31:04 +0300
commit325cdacd03c12629aa5f9ee2ace49b1f3dc184a8 (patch)
treef9bafe49be8aa9e98a0afb4a4a4009e5d4a7561f /arch/powerpc
parent095f6d76221dd4b99d004e4c826ac4382c6ce5e3 (diff)
downloadlinux-325cdacd03c12629aa5f9ee2ace49b1f3dc184a8.tar.xz
debug: Fix WARN_ON_ONCE() for modules
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@gmx.de> Tested-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 19d436268dde ("debug: Add _ONCE() logic to report_bug()") Link: http://lkml.kernel.org/r/a53b04235a65478dd9afc51f5b329fdc65c84364.1500095401.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/asm/bug.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 0151af6c2a50..87fcc1948817 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" \