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x86: Call fixup_exception() before notify_die() in math_error()
fpu__drop() has an explicit fwait which under some conditions can trigger a fixable FPU exception while in kernel. Thus, we should attempt to fixup the exception first, and only call notify_die() if the fixup failed just like in do_general_protection(). The original call sequence incorrectly triggers KDB entry on debug kernels under particular FPU-intensive workloads. Andy noted, that this makes the whole conditional irq enable thing even more inconsistent, but fixing that it outside the scope of this. Signed-off-by: Siarhei Liakh <siarhei.liakh@concurrent-rt.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Borislav Petkov" <bpetkov@suse.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/DM5PR11MB201156F1CAB2592B07C79A03B17D0@DM5PR11MB2011.namprd11.prod.outlook.com
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1 changed files with 8 additions and 6 deletions
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@ -834,16 +834,18 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
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char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" :
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"simd exception";
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if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP)
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return;
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cond_local_irq_enable(regs);
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if (!user_mode(regs)) {
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if (!fixup_exception(regs, trapnr)) {
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task->thread.error_code = error_code;
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task->thread.trap_nr = trapnr;
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if (fixup_exception(regs, trapnr))
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return;
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task->thread.error_code = error_code;
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task->thread.trap_nr = trapnr;
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if (notify_die(DIE_TRAP, str, regs, error_code,
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trapnr, SIGFPE) != NOTIFY_STOP)
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die(str, regs, error_code);
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}
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return;
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}
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