Re: [PATCH] linux-user/riscv: fix up struct target_ucontext definition

[LIU Zhiwei]

    Ping.
    
    When I port RISU, I find this bug. I can't get the correct registers
    from the
    struct ucontext_t parameter in the signal handler.
    
    If you want to reproduce it, just   register a signal handler for
    SIGILL,
    and  output an illegal instruction, such as
    
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <signal.h>
#include <ucontext.h>

void sigill(int sig, siginfo_t *si, void *uc)
{
    printf("Illegal pc: %016" PRIx64 "\n",
           ((ucontext_t *)uc)->uc_mcontext.__gregs[0]);
}

static void set_sigill_handler(void (*fn) (int, siginfo_t *, void *))
{
    struct sigaction sa;
    memset(&sa, 0, sizeof(struct sigaction));

    sa.sa_sigaction = fn;
    sa.sa_flags = SA_SIGINFO;
    sigemptyset(&sa.sa_mask);
    if (sigaction(SIGILL, &sa, 0) != 0) {
        perror("sigaction");
        exit(1);
    }
}

int main()
{
    set_sigill_handler(sigill);
    asm(".dword 0x0000006b");
    return 0;
}
~                                                                                                                                                                                                        
    Zhiwei

On 2020/4/12 10:08, LIU Zhiwei wrote:

> As struct target_ucontext will be transfered to signal handler, it
> must keep pace with struct ucontext_t defined in Linux kernel.
>
> Signed-off-by: LIU Zhiwei <address@hidden>
> ---
>  linux-user/riscv/signal.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
> index 83ecc6f799..67a95dbc7b 100644
> --- a/linux-user/riscv/signal.c
> +++ b/linux-user/riscv/signal.c
> @@ -40,8 +40,9 @@ struct target_ucontext {
>      unsigned long uc_flags;
>      struct target_ucontext *uc_link;
>      target_stack_t uc_stack;
> -    struct target_sigcontext uc_mcontext;
>      target_sigset_t uc_sigmask;
> +    uint8_t   __unused[1024 / 8 - sizeof(target_sigset_t)];
> +    struct target_sigcontext uc_mcontext QEMU_ALIGNED(16);
>  };
>  
>  struct target_rt_sigframe {
>