> On Jan 24, 2022, at 6:29 PM, Warner Losh <i...@bsdimp.com> wrote:
>
> Implements the meat of a sigreturn(2) system call via do_sigreturn, and
> helper reset_signal_mask. Fix the prototype of do_sigreturn in qemu.h
> and remove do_rt_sigreturn since it's linux only.
>
> Signed-off-by: Stacey Son <s...@freebsd.org>
> Signed-off-by: Kyle Evans <kev...@freebsd.org>
> Signed-off-by: Warner Losh <i...@bsdimp.com>
>
> PENDING COMMENTS: from Peter Maydell <peter.mayd...@linaro.org>
>
> do_sigreturn() itself shouldn't be setting the active signal
> mask, at least if you follow the linux-user design. It just
> sets the thread's signal_mask field in the TaskState by
> calling set_sigmask(), and then on our way out in the
> main cpu loop we'll call process_pending_signals() which
> sets the real thread signal mask to that value. (This, together
> with do_sigreturn() calling block_signals() before it starts
> work, avoids some race conditions where a host signal is delivered
> as soon as we unblock, I think.)
I think this is correct. We’re already setting the signal_mask element
in a mostly similar way to linux-user, so all I need to do is to remove the
setting the actual signal mask. The rest of this is already in place. I’ll
included in v3.
Warner
> ---
> bsd-user/signal-common.h | 2 +-
> bsd-user/signal.c | 56 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 57 insertions(+), 1 deletion(-)
>
> diff --git a/bsd-user/signal-common.h b/bsd-user/signal-common.h
> index ee819266f54..786ec592d18 100644
> --- a/bsd-user/signal-common.h
> +++ b/bsd-user/signal-common.h
> @@ -11,7 +11,7 @@
>
> long do_rt_sigreturn(CPUArchState *env);
> abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong
> sp);
> -long do_sigreturn(CPUArchState *env);
> +long do_sigreturn(CPUArchState *env, abi_ulong addr);
> void force_sig_fault(int sig, int code, abi_ulong addr);
> int host_to_target_signal(int sig);
> void host_to_target_sigset(target_sigset_t *d, const sigset_t *s);
> diff --git a/bsd-user/signal.c b/bsd-user/signal.c
> index 9ec4354d232..05caf812ccb 100644
> --- a/bsd-user/signal.c
> +++ b/bsd-user/signal.c
> @@ -626,6 +626,62 @@ static void setup_frame(int sig, int code, struct
> target_sigaction *ka,
> unlock_user_struct(frame, frame_addr, 1);
> }
>
> +static int reset_signal_mask(target_ucontext_t *ucontext)
> +{
> + int i;
> + sigset_t blocked;
> + target_sigset_t target_set;
> + TaskState *ts = (TaskState *)thread_cpu->opaque;
> +
> + for (i = 0; i < TARGET_NSIG_WORDS; i++)
> + if (__get_user(target_set.__bits[i],
> + &ucontext->uc_sigmask.__bits[i])) {
> + return -TARGET_EFAULT;
> + }
> + target_to_host_sigset_internal(&blocked, &target_set);
> + ts->signal_mask = blocked;
> + sigprocmask(SIG_SETMASK, &ts->signal_mask, NULL);
> +
> + return 0;
> +}
> +
> +/* See sys/$M/$M/exec_machdep.c sigreturn() */
> +long do_sigreturn(CPUArchState *env, abi_ulong addr)
> +{
> + long ret;
> + abi_ulong target_ucontext;
> + target_ucontext_t *ucontext = NULL;
> +
> + /* Get the target ucontext address from the stack frame */
> + ret = get_ucontext_sigreturn(env, addr, &target_ucontext);
> + if (is_error(ret)) {
> + return ret;
> + }
> + trace_user_do_sigreturn(env, addr);
> + if (!lock_user_struct(VERIFY_READ, ucontext, target_ucontext, 0)) {
> + goto badframe;
> + }
> +
> + /* Set the register state back to before the signal. */
> + if (set_mcontext(env, &ucontext->uc_mcontext, 1)) {
> + goto badframe;
> + }
> +
> + /* And reset the signal mask. */
> + if (reset_signal_mask(ucontext)) {
> + goto badframe;
> + }
> +
> + unlock_user_struct(ucontext, target_ucontext, 0);
> + return -TARGET_EJUSTRETURN;
> +
> +badframe:
> + if (ucontext != NULL) {
> + unlock_user_struct(ucontext, target_ucontext, 0);
> + }
> + return -TARGET_EFAULT;
> +}
> +
> void signal_init(void)
> {
> TaskState *ts = (TaskState *)thread_cpu->opaque;
> --
> 2.33.1
>
