diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2017-07-15 00:10:58 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-07-20 12:31:04 +0200 |
| commit | 325cdacd03c12629aa5f9ee2ace49b1f3dc184a8 (patch) | |
| tree | f9bafe49be8aa9e98a0afb4a4a4009e5d4a7561f /arch/x86 | |
| parent | 095f6d76221dd4b99d004e4c826ac4382c6ce5e3 (diff) | |
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/x86')
| -rw-r--r-- | arch/x86/include/asm/bug.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index 39e702d90cdb..aa6b2023d8f8 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" \ |