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Commit 325cdacd authored Jul 15, 2017 by Josh Poimboeuf Committed by Ingo Molnar Jul 20, 2017

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:

  19d43626 ("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: 19d43626 ("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>

parent 095f6d76

arch/arm/include/asm/bug.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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" \

arch/arm64/include/asm/bug.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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__) \

arch/blackfin/include/asm/bug.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -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" \

arch/mn10300/include/asm/bug.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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" \
		: \

arch/parisc/include/asm/bug.h

+3 −3

Original line number	Diff line number	Diff line
		@@ -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" \