Re: [Qemu-devel] [PATCH] Actually block signals that have been queued by Qemu.

[Peter Maydell]

On 8 March 2015 at 04:18, Timothy Baldwin
<address@hidden> wrote:
> From ebcb08f4f4ed90c8557cafc02593360c59e10a49 Mon Sep 17 00:00:00 2001
> From: Timothy E Baldwin <address@hidden>
> Date: Sat, 7 Mar 2015 18:42:41 +0000
> Subject: [PATCH] Actually block signals that have been queued in TaskState.
>
> Actually block signals that have been queued in TaskState.
> For this purpose the set of block signals is stored in TaskState.
>
> Fixes bug #1429313
>
> Signed-off-by: Timothy Baldwin <address@hidden>
> ---
>  linux-user/qemu.h   |  2 +-
>  linux-user/signal.c | 39 ++++++++++++++++++++-------------------
>  2 files changed, 21 insertions(+), 20 deletions(-)
>
> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
> index 8012cc2..7de543b 100644
> --- a/linux-user/qemu.h
> +++ b/linux-user/qemu.h
> @@ -127,13 +127,13 @@ typedef struct TaskState {
>  #endif
>      uint32_t stack_base;
>      int used; /* non zero if used */
> -    bool sigsegv_blocked; /* SIGSEGV blocked by guest */
>      struct image_info *info;
>      struct linux_binprm *bprm;
>       struct emulated_sigtable sigtab[TARGET_NSIG];
>      struct sigqueue sigqueue_table[MAX_SIGQUEUE_SIZE]; /* siginfo queue */
>      struct sigqueue *first_free; /* first free siginfo queue entry */
> +    sigset_t signal_mask;
>      int signal_pending; /* non zero if a signal may be pending */
>  } __attribute__((aligned(16))) TaskState;
>  diff --git a/linux-user/signal.c b/linux-user/signal.c
> index 5bb399e..0997c45 100644
> --- a/linux-user/signal.c
> +++ b/linux-user/signal.c
> @@ -209,40 +209,38 @@ int do_sigprocmask(int how, const sigset_t *set,
> sigset_t *oldset)
>      sigset_t *temp = NULL;
>      CPUState *cpu = thread_cpu;
>      TaskState *ts = (TaskState *)cpu->opaque;
> -    bool segv_was_blocked = ts->sigsegv_blocked;
> +
> +    if (oldset) {
> +        *oldset = ts->signal_mask;
> +    }
>       if (set) {
> -        bool has_sigsegv = sigismember(set, SIGSEGV);
>          val = *set;
>          temp = &val;
> -
> -        sigdelset(temp, SIGSEGV);
> +        int i;
>           switch (how) {
>          case SIG_BLOCK:
> -            if (has_sigsegv) {
> -                ts->sigsegv_blocked = true;
> -            }
> +            sigorset(&ts->signal_mask, &ts->signal_mask, &val);
>              break;
>          case SIG_UNBLOCK:
> -            if (has_sigsegv) {
> -                ts->sigsegv_blocked = false;
> +            /* There appears to be no signotset() */
> +            for(i = 0; i != sizeof(val.__val) / sizeof(val.__val[0]); ++i)
> {
> +                ts->signal_mask.__val[i] &= ~val.__val[i];
>              }

You can't go messing around in the internals of the glibc representation
like this. You need to use the public API functions, which in this case
means looping around calling sigdelset().

-- PMM