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authorHuacai Chen <chenhc@lemote.com>2014-07-16 09:19:16 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-09-17 09:03:58 -0700
commitf020cedd010180e759cb6cce817b8a60ea6311a1 (patch)
tree08e1d831e537bf8d34840e93c38cb157f923f7f3 /arch
parent33103cff2cb6a6f2753676ed9f82c4e3e7fe4e42 (diff)
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')
-rw-r--r--arch/mips/kernel/unaligned.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c
index 203d8857070d..2c81265bcf46 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, &current->thread.fpu, 1,