3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: "Maciej W. Rozycki" macro@linux-mips.org
commit 443c44032a54f9acf027a8e688380fddc809bc19 upstream.
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 [bwh: Backported to 3.16: drop changes in mips-r2-to-r6-emul and simulate_fp()] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -775,7 +775,7 @@ asmlinkage void do_fpe(struct pt_regs *r
/* * 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;
@@ -1292,6 +1292,13 @@ asmlinkage void do_cpu(struct pt_regs *r 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(); }