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SubjectRe: [PATCH] MIPS: Fix IRQ tracing when call handle_fpe()
On Tue, May 26, 2020 at 03:07:16PM +0800, yuanjunqing wrote:
>
> 在 2020/5/25 下午4:42, Thomas Bogendoerfer 写道:
> > 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 ?
> >
>
> yes, it can work when we just move the cfc1 below TRACE_IRQS_OFF,
>  and the code is written as follows.
>
> CLI
> TRACE_IRQS_OFF
> .set mips1
> SET_HARDFLOAT
> cfc1 a1, fcr31
> .set pop
>   .endm

good, could we do the same with _cfcmsa a1, MSA_CSR in the msa case ?

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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