64 lines
2.1 KiB
Diff
64 lines
2.1 KiB
Diff
From: Huacai Chen <chenhc@lemote.com>
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Date: Wed, 16 Jul 2014 09:19:16 +0800
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Subject: MIPS: Remove BUG_ON(!is_fpu_owner()) in do_ade()
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Origin: https://git.kernel.org/linus/2e5767a27337812f6850b3fa362419e2f085e5c3
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In do_ade(), is_fpu_owner() isn't preempt-safe. For example, when an
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unaligned ldc1 is executed, do_cpu() is called and then FPU will be
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enabled (and TIF_USEDFPU will be set for the current process). Then,
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do_ade() is called because the access is unaligned. If the current
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process is preempted at this time, TIF_USEDFPU will be cleard. So when
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the process is scheduled again, BUG_ON(!is_fpu_owner()) is triggered.
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This small program can trigger this BUG in a preemptible kernel:
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int main (int argc, char *argv[])
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{
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double u64[2];
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while (1) {
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asm volatile (
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".set push \n\t"
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".set noreorder \n\t"
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"ldc1 $f3, 4(%0) \n\t"
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".set pop \n\t"
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::"r"(u64):
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);
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}
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return 0;
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}
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V2: Remove the BUG_ON() unconditionally due to Paul's suggestion.
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Signed-off-by: Huacai Chen <chenhc@lemote.com>
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Signed-off-by: Jie Chen <chenj@lemote.com>
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Signed-off-by: Rui Wang <wangr@lemote.com>
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Cc: <stable@vger.kernel.org>
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Cc: John Crispin <john@phrozen.org>
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Cc: Steven J. Hill <Steven.Hill@imgtec.com>
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Cc: linux-mips@linux-mips.org
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Cc: Fuxin Zhang <zhangfx@lemote.com>
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Cc: Zhangjin Wu <wuzhangjin@gmail.com>
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Cc: stable@vger.kernel.org
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Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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---
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arch/mips/kernel/unaligned.c | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c
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index 2b35172..e11906d 100644
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--- a/arch/mips/kernel/unaligned.c
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+++ b/arch/mips/kernel/unaligned.c
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@@ -690,7 +690,6 @@ static void emulate_load_store_insn(struct pt_regs *regs,
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case sdc1_op:
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die_if_kernel("Unaligned FP access in kernel code", regs);
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BUG_ON(!used_math());
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- BUG_ON(!is_fpu_owner());
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lose_fpu(1); /* Save FPU state for the emulator. */
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res = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1,
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--
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1.7.10.4
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