From 443c44032a54f9acf027a8e688380fddc809bc19 Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Fri, 3 Apr 2015 23:27:10 +0100 Subject: [PATCH] MIPS: Always clear FCSR cause bits after emulation Clear any FCSR cause bits recorded in the saved FPU context after emulation in all cases rather than in `do_fpe' only, so that any unmasked IEEE 754 exception left from emulation does not cause a fatal kernel-mode FPE hardware exception with the CTC1 instruction used by the kernel to subsequently restore FCSR hardware from the saved FPU context. Signed-off-by: Maciej W. Rozycki Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9704/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/mips-r2-to-r6-emul.c | 6 ++++++ arch/mips/kernel/traps.c | 15 ++++++++++++++- 2 files changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/mips/kernel/mips-r2-to-r6-emul.c b/arch/mips/kernel/mips-r2-to-r6-emul.c index f1d1b42d1902..6633fa97d431 100644 --- a/arch/mips/kernel/mips-r2-to-r6-emul.c +++ b/arch/mips/kernel/mips-r2-to-r6-emul.c @@ -1169,6 +1169,12 @@ fpu_emul: err = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 0, &fault_addr); + /* + * We can't allow the emulated instruction to leave any of + * the cause bits set in $fcr31. + */ + current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X; + /* * this is a tricky issue - lose_fpu() uses LL/SC atomics * if FPU is owned and effectively cancels user level LL/SC. diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c index dbfa47cdc8c1..4a0552dbcf4a 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -761,6 +761,12 @@ static int simulate_fp(struct pt_regs *regs, unsigned int opcode, sig = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 1, &fault_addr); + /* + * We can't allow the emulated instruction to leave any of + * the cause bits set in $fcr31. + */ + current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X; + /* If something went wrong, signal */ process_fpemu_return(sig, fault_addr); @@ -807,7 +813,7 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31) /* * We can't allow the emulated instruction to leave any of - * the cause bit set in $fcr31. + * the cause bits set in $fcr31. */ current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X; @@ -1384,6 +1390,13 @@ asmlinkage void do_cpu(struct pt_regs *regs) sig = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 0, &fault_addr); + + /* + * We can't allow the emulated instruction to leave + * any of the cause bits set in $fcr31. + */ + current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X; + if (!process_fpemu_return(sig, fault_addr) && !err) mt_ase_fp_affinity(); } -- 2.20.1