Re: [Qemu-devel] [PATCH v15 5/5] linux-user: Handle EXCP_FPE properly for MIPS

[Laurent Vivier <laurent@vivier.eu>]

Le 28/06/2019 à 10:54, Aleksandar Markovic a écrit :
> From: Aleksandar Markovic <amarkovic@wavecomp.com>
> 
> Handle EXCP_FPE properly for MIPS in cpu loop.
> 
> Note that a vast majority of FP instructions are not affected by
> the absence of the code in this patch, as they use alternative code
> paths for handling floating point exceptions (see, for example,
> invocations of update_fcr31()) - they rely on softfloat library for
> keeping track on exceptions that needs to be raised. However, there
> are few MIPS FP instructions (an example is CTC1) that use function
> do_raise_exception() directly, and they need the case that is added
> in this patch to propagate the FPE exception as designed.
> 
> The code is based on kernel's function force_fcr31_sig() in
> arch/mips/kernel.traps.c.
> 
> Reported-by: Yunqiang Su <ysu@wavecomp.com>
> Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
> ---
>  linux-user/mips/cpu_loop.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/linux-user/mips/cpu_loop.c b/linux-user/mips/cpu_loop.c
> index 43ba267..0ba894f 100644
> --- a/linux-user/mips/cpu_loop.c
> +++ b/linux-user/mips/cpu_loop.c
> @@ -540,6 +540,23 @@ done_syscall:
>              info.si_code = TARGET_ILL_ILLOPC;
>              queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
>              break;
> +        case EXCP_FPE:
> +            info.si_signo = TARGET_SIGFPE;
> +            info.si_errno = 0;
> +            info.si_code = TARGET_FPE_FLTUNK;
> +            if (GET_FP_CAUSE(env->active_fpu.fcr31) & FP_INVALID) {
> +                info.si_code = TARGET_FPE_FLTINV;
> +            } else if (GET_FP_CAUSE(env->active_fpu.fcr31) & FP_DIV0) {
> +                info.si_code = TARGET_FPE_FLTDIV;
> +            } else if (GET_FP_CAUSE(env->active_fpu.fcr31) & FP_OVERFLOW) {
> +                info.si_code = TARGET_FPE_FLTOVF;
> +            } else if (GET_FP_CAUSE(env->active_fpu.fcr31) & FP_UNDERFLOW) {
> +                info.si_code = TARGET_FPE_FLTUND;
> +            } else if (GET_FP_CAUSE(env->active_fpu.fcr31) & FP_INEXACT) {
> +                info.si_code = TARGET_FPE_FLTRES;
> +            }
> +            queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
> +            break;
>          /* The code below was inspired by the MIPS Linux kernel trap
>           * handling code in arch/mips/kernel/traps.c.
>           */
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>