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
--- a/arch/mips/kernel/mips-r2-to-r6-emul.c
+++ b/arch/mips/kernel/mips-r2-to-r6-emul.c
@@ -1170,6 +1170,12 @@
&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.
* So, it could be logical to don't restore FPU ownership here.