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| author | Huacai Chen <chenhc@lemote.com> | 2014-07-16 09:19:16 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-09-17 09:03:58 -0700 |
| commit | f020cedd010180e759cb6cce817b8a60ea6311a1 (patch) | |
| tree | 08e1d831e537bf8d34840e93c38cb157f923f7f3 /arch/mips | |
| parent | 33103cff2cb6a6f2753676ed9f82c4e3e7fe4e42 (diff) | |
| download | linux-3.10-f020cedd010180e759cb6cce817b8a60ea6311a1.tar.gz linux-3.10-f020cedd010180e759cb6cce817b8a60ea6311a1.tar.bz2 linux-3.10-f020cedd010180e759cb6cce817b8a60ea6311a1.zip | |
MIPS: Remove BUG_ON(!is_fpu_owner()) in do_ade()
commit 2e5767a27337812f6850b3fa362419e2f085e5c3 upstream.
In do_ade(), is_fpu_owner() isn't preempt-safe. For example, when an
unaligned ldc1 is executed, do_cpu() is called and then FPU will be
enabled (and TIF_USEDFPU will be set for the current process). Then,
do_ade() is called because the access is unaligned. If the current
process is preempted at this time, TIF_USEDFPU will be cleard. So when
the process is scheduled again, BUG_ON(!is_fpu_owner()) is triggered.
This small program can trigger this BUG in a preemptible kernel:
int main (int argc, char *argv[])
{
double u64[2];
while (1) {
asm volatile (
".set push \n\t"
".set noreorder \n\t"
"ldc1 $f3, 4(%0) \n\t"
".set pop \n\t"
::"r"(u64):
);
}
return 0;
}
V2: Remove the BUG_ON() unconditionally due to Paul's suggestion.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Jie Chen <chenj@lemote.com>
Signed-off-by: Rui Wang <wangr@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/kernel/unaligned.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c index 203d8857070..2c81265bcf4 100644 --- a/arch/mips/kernel/unaligned.c +++ b/arch/mips/kernel/unaligned.c @@ -604,7 +604,6 @@ static void emulate_load_store_insn(struct pt_regs *regs, case sdc1_op: die_if_kernel("Unaligned FP access in kernel code", regs); BUG_ON(!used_math()); - BUG_ON(!is_fpu_owner()); lose_fpu(1); /* Save FPU state for the emulator. */ res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1, |