x86: Fix compilation bug in kprobes' twobyte_is_boostable
When compiling an i386_defconfig kernel with gcc-4.6.1-9.fc15.i686, I noticed a warning about the asm operand for test_bit in kprobes' can_boost. I discovered that this caused only the first long of twobyte_is_boostable[] to be output. Jakub filed and fixed gcc PR50571 to correct the warning and this output issue. But to solve it for less current gcc, we can make kprobes' twobyte_is_boostable[] non-const, and it won't be optimized out. Before: CC arch/x86/kernel/kprobes.o In file included from include/linux/bitops.h:22:0, from include/linux/kernel.h:17, from [...]/arch/x86/include/asm/percpu.h:44, from [...]/arch/x86/include/asm/current.h:5, from [...]/arch/x86/include/asm/processor.h:15, from [...]/arch/x86/include/asm/atomic.h:6, from include/linux/atomic.h:4, from include/linux/mutex.h:18, from include/linux/notifier.h:13, from include/linux/kprobes.h:34, from arch/x86/kernel/kprobes.c:43: [...]/arch/x86/include/asm/bitops.h: In function ‘can_boost.part.1’: [...]/arch/x86/include/asm/bitops.h:319:2: warning: use of memory input without lvalue in asm operand 1 is deprecated [enabled by default] $ objdump -rd arch/x86/kernel/kprobes.o | grep -A1 -w bt 551: 0f a3 05 00 00 00 00 bt %eax,0x0 554: R_386_32 .rodata.cst4 $ objdump -s -j .rodata.cst4 -j .data arch/x86/kernel/kprobes.o arch/x86/kernel/kprobes.o: file format elf32-i386 Contents of section .data: 0000 48000000 00000000 00000000 00000000 H............... Contents of section .rodata.cst4: 0000 4c030000 L... Only a single long of twobyte_is_boostable[] is in the object file. After, without the const on twobyte_is_boostable: $ objdump -rd arch/x86/kernel/kprobes.o | grep -A1 -w bt 551: 0f a3 05 20 00 00 00 bt %eax,0x20 554: R_386_32 .data $ objdump -s -j .rodata.cst4 -j .data arch/x86/kernel/kprobes.o arch/x86/kernel/kprobes.o: file format elf32-i386 Contents of section .data: 0000 48000000 00000000 00000000 00000000 H............... 0010 00000000 00000000 00000000 00000000 ................ 0020 4c030000 0f000200 ffff0000 ffcff0c0 L............... 0030 0000ffff 3bbbfff8 03ff2ebb 26bb2e77 ....;.......&..w Now all 32 bytes are output into .data instead. Signed-off-by: Josh Stone <jistone@redhat.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
c3b92c8787
commit
315eb8a2a1
|
@ -75,8 +75,10 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
|
|||
/*
|
||||
* Undefined/reserved opcodes, conditional jump, Opcode Extension
|
||||
* Groups, and some special opcodes can not boost.
|
||||
* This is non-const to keep gcc from statically optimizing it out, as
|
||||
* variable_test_bit makes gcc think only *(unsigned long*) is used.
|
||||
*/
|
||||
static const u32 twobyte_is_boostable[256 / 32] = {
|
||||
static u32 twobyte_is_boostable[256 / 32] = {
|
||||
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
|
||||
/* ---------------------------------------------- */
|
||||
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
|
||||
|
|
Loading…
Reference in New Issue