Re: [PATCH v2 2/7] linux-user/nios2: Fixes for signal frame setup

[Laurent Vivier <laurent@vivier.eu>]

Le 21/12/2021 à 03:50, Richard Henderson a écrit :
> Do not confuse host and guest addresses.  Lock and unlock
> the target_rt_sigframe structure in setup_rt_sigframe.
> 
> Since rt_setup_ucontext always returns 0, drop the return
> value entirely.  This eliminates the only write to the err
> variable in setup_rt_sigframe.
> 
> Always copy the siginfo structure.
> 
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/nios2/signal.c | 49 ++++++++++++++++-----------------------
>   1 file changed, 20 insertions(+), 29 deletions(-)
> 
> diff --git a/linux-user/nios2/signal.c b/linux-user/nios2/signal.c
> index a77e8a40f4..adbffe32e3 100644
> --- a/linux-user/nios2/signal.c
> +++ b/linux-user/nios2/signal.c
> @@ -42,7 +42,7 @@ struct target_rt_sigframe {
>       struct target_ucontext uc;
>   };
>   
> -static int rt_setup_ucontext(struct target_ucontext *uc, CPUNios2State *env)
> +static void rt_setup_ucontext(struct target_ucontext *uc, CPUNios2State *env)
>   {
>       unsigned long *gregs = uc->tuc_mcontext.gregs;
>   
> @@ -75,8 +75,6 @@ static int rt_setup_ucontext(struct target_ucontext *uc, CPUNios2State *env)
>       __put_user(env->regs[R_GP], &gregs[25]);
>       __put_user(env->regs[R_EA], &gregs[27]);
>       __put_user(env->regs[R_SP], &gregs[28]);
> -
> -    return 0;
>   }
>   
>   static int rt_restore_ucontext(CPUNios2State *env, struct target_ucontext *uc,
> @@ -135,8 +133,8 @@ static int rt_restore_ucontext(CPUNios2State *env, struct target_ucontext *uc,
>       return 0;
>   }
>   
> -static void *get_sigframe(struct target_sigaction *ka, CPUNios2State *env,
> -                          size_t frame_size)
> +static abi_ptr get_sigframe(struct target_sigaction *ka, CPUNios2State *env,
> +                            size_t frame_size)
>   {
>       unsigned long usp;
>   
> @@ -144,7 +142,7 @@ static void *get_sigframe(struct target_sigaction *ka, CPUNios2State *env,
>       usp = target_sigsp(get_sp_from_cpustate(env), ka);
>   
>       /* Verify, is it 32 or 64 bit aligned */
> -    return (void *)((usp - frame_size) & -8UL);
> +    return (usp - frame_size) & -8;
>   }
>   
>   void setup_rt_frame(int sig, struct target_sigaction *ka,
> @@ -153,26 +151,25 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>                       CPUNios2State *env)
>   {
>       struct target_rt_sigframe *frame;
> -    int i, err = 0;
> +    abi_ptr frame_addr;
> +    int i;
>   
> -    frame = get_sigframe(ka, env, sizeof(*frame));
> -
> -    if (ka->sa_flags & SA_SIGINFO) {
> -        tswap_siginfo(&frame->info, info);
> +    frame_addr = get_sigframe(ka, env, sizeof(*frame));
> +    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
> +        force_sigsegv(sig);
> +        return;
>       }
>   
> +    tswap_siginfo(&frame->info, info);
> +
>       /* Create the ucontext.  */
>       __put_user(0, &frame->uc.tuc_flags);
>       __put_user(0, &frame->uc.tuc_link);
>       target_save_altstack(&frame->uc.tuc_stack, env);
> -    err |= rt_setup_ucontext(&frame->uc, env);
> +    rt_setup_ucontext(&frame->uc, env);
>       for (i = 0; i < TARGET_NSIG_WORDS; i++) {
>           __put_user((abi_ulong)set->sig[i],
> -            (abi_ulong *)&frame->uc.tuc_sigmask.sig[i]);
> -    }
> -
> -    if (err) {
> -        goto give_sigsegv;
> +                   (abi_ulong *)&frame->uc.tuc_sigmask.sig[i]);
>       }
>   
>       /* Set up to return from userspace; jump to fixed address sigreturn
> @@ -180,19 +177,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>       env->regs[R_RA] = (unsigned long) (0x1044);
>   
>       /* Set up registers for signal handler */
> -    env->regs[R_SP] = (unsigned long) frame;
> -    env->regs[4] = (unsigned long) sig;
> -    env->regs[5] = (unsigned long) &frame->info;
> -    env->regs[6] = (unsigned long) &frame->uc;
> -    env->regs[R_EA] = (unsigned long) ka->_sa_handler;
> -    return;
> +    env->regs[R_SP] = frame_addr;
> +    env->regs[4] = sig;
> +    env->regs[5] = frame_addr + offsetof(struct target_rt_sigframe, info);
> +    env->regs[6] = frame_addr + offsetof(struct target_rt_sigframe, uc);
> +    env->regs[R_EA] = ka->_sa_handler;
>   
> -give_sigsegv:
> -    if (sig == TARGET_SIGSEGV) {
> -        ka->_sa_handler = TARGET_SIG_DFL;
> -    }
> -    force_sigsegv(sig);
> -    return;
> +    unlock_user_struct(frame, frame_addr, 1);
>   }
>   
>   long do_sigreturn(CPUNios2State *env)


Applied to my linux-user-for-7.0 branch.

Thanks,
Laurent