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SubjectRe: [PATCH] MIPS: Fix IRQ tracing when call handle_fpe()
On Mon, May 25, 2020 at 11:31:23AM +0800, YuanJunQing wrote:
> Register "a1" is unsaved in this function,
> when CONFIG_TRACE_IRQFLAGS is enabled,
> the TRACE_IRQS_OFF macro will call trace_hardirqs_off(),
> and this may change register "a1".
> The variment of register "a1" may send SIGFPE signal
> to task when call do_fpe(),and this may kill the task.
>
> Signed-off-by: YuanJunQing <yuanjunqing66@163.com>
> ---
> arch/mips/kernel/genex.S | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
> index 8236fb291e3f..956a76429773 100644
> --- a/arch/mips/kernel/genex.S
> +++ b/arch/mips/kernel/genex.S
> @@ -480,16 +480,18 @@ NESTED(nmi_handler, PT_SIZE, sp)
> /* gas fails to assemble cfc1 for some archs (octeon).*/ \
> .set mips1
> SET_HARDFLOAT
> - cfc1 a1, fcr31
> + cfc1 s0, fcr31
> .set pop
> CLI
> TRACE_IRQS_OFF
> + move a1,s0
> .endm

do we realy need to read fcr31 that early ? Wouldn't it work to
just move the cfc1 below TRACE_IRQS_OFF ?

Thomas.

--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]

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