Re: PROBLEM: Caught SIGFPE exceptions aren't reset

[Chuck Ebbert <cebbert@redhat.com>]

On 08/25/2007 01:31 PM, Clark Cooper wrote:
>> Your handler can do this by masking
>>  exceptions, changing the operands of the failed FP instruction,
>> or by changing the PC so that the failed instruction is skipped
>> (your handler may want to emulate the instruction in this case).
> 
> Given the current SIGFPE handling in the kernel, a userland handler
> CAN'T mask the exceptions or clear the exception flags. This is
> demonstrated in my example program where I call both feclearexception
> and fedisableexception in the handler. The reason these don't work is
> that any change you make to these FPU registers is overwritten with
> the saved FPU context on return from the signal handler. Changing the
> PC won't help since the exception flag is still set and unmasked on
> signal return.

Just change the saved FPU context before returning. (It's on the stack
when your handler is running.)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/