Re: [PATCH v2 19/41] hw/core: Add TCGCPUOps.record_sigsegv

[Philippe Mathieu-Daudé]

On 9/18/21 20:45, Richard Henderson wrote:
> Add a new user-only interface for updating cpu state before
> raising a signal.  This will replace tlb_fill for user-only
> and should result in less boilerplate for each guest.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/hw/core/tcg-cpu-ops.h | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/include/hw/core/tcg-cpu-ops.h b/include/hw/core/tcg-cpu-ops.h
> index 4a4c4053e3..e229a40772 100644
> --- a/include/hw/core/tcg-cpu-ops.h
> +++ b/include/hw/core/tcg-cpu-ops.h
> @@ -114,6 +114,32 @@ struct TCGCPUOps {
>       */
>      bool (*io_recompile_replay_branch)(CPUState *cpu,
>                                         const TranslationBlock *tb);
> +#else
> +    /**
> +     * record_sigsegv:
> +     * @cpu: cpu context
> +     * @addr: faulting guest address
> +     * @access_type: access was read/write/execute
> +     * @maperr: true for invalid page, false for permission fault
> +     * @ra: host pc for unwinding
> +     *
> +     * We are about to raise SIGSEGV with si_code set for @maperr,
> +     * and si_addr set for @addr.  Record anything further needed
> +     * for the signal ucontext_t.
> +     *
> +     * If the emulated kernel does not provide anything to the signal
> +     * handler with anything besides the user context registers, and
> +     * the siginfo_t, then this hook need do nothing and may be omitted.
> +     * Otherwise, record the data and return; the caller will raise
> +     * the signal, unwind the cpu state, and return to the main loop.
> +     *
> +     * If it is simpler to re-use the sysemu tlb_fill code, @ra is provided
> +     * so that a "normal" cpu exception can be raised.  In this case,
> +     * the signal must be raised by the architecture cpu_loop.
> +     */

Shouldn't it have the QEMU_NORETURN attribute?

> +    void (*record_sigsegv)(CPUState *cpu, vaddr addr,
> +                           MMUAccessType access_type,
> +                           bool maperr, uintptr_t ra);
>  #endif /* CONFIG_SOFTMMU */
>  #endif /* NEED_CPU_H */
>  
>