From 76e5846d3bdf59eb1010d5607003da2dc3910bb1 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Mon, 1 Feb 2016 13:50:36 +0000 Subject: [PATCH] MIPS: Properly disable FPU in start_thread() start_thread() (called for execve(2)) clears the TIF_USEDFPU flag without atomically disabling the FPU. With a preemptive kernel, an unfortunately timed preemption after this could result in another task (or KVM guest) being scheduled in with the FPU still enabled, since lose_fpu_inatomic() only turns it off if TIF_USEDFPU is set. Use lose_fpu(0) instead of the separate FPU / MSA management, which should do the right thing (drop FPU properly and atomically without saving state) and will be more future proof. Signed-off-by: James Hogan Reviewed-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/12302/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/process.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index f2975d4..eddd5fd 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -65,12 +65,10 @@ void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp) status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK); status |= KU_USER; regs->cp0_status = status; + lose_fpu(0); + clear_thread_flag(TIF_MSA_CTX_LIVE); clear_used_math(); - clear_fpu_owner(); init_dsp(); - clear_thread_flag(TIF_USEDMSA); - clear_thread_flag(TIF_MSA_CTX_LIVE); - disable_msa(); regs->cp0_epc = pc; regs->regs[29] = sp; } -- 2.7.4