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 <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9704/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/mips-r2-to-r6-emul.c b/arch/mips/kernel/mips-r2-to-r6-emul.c
index f1d1b42..6633fa9 100644 (file)
--- 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, &current->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 --cc arch/mips/kernel/traps.c
Simple merge