Re: [PATCH 23/30] bsd-user/signal.c: sigset manipulation routines.

[Peter Maydell]

On Sun, 9 Jan 2022 at 16:53, Warner Losh <imp@bsdimp.com> wrote:
>
> target_sigemptyset: resets a set to having no bits set
> qemu_sigorset:      computes the or of two sets
> target_sigaddset:   adds a signal to a set
> target_sigismember: returns true when signal is a member
> host_to_target_sigset_internal: convert host sigset to target
> host_to_target_sigset: convert host sigset to target
> target_to_host_sigset_internal: convert target sigset to host
> target_to_host_sigset: convert target sigset to host
>
> Signed-off-by: Stacey Son <sson@FreeBSD.org>
> Signed-off-by: Kyle Evans <kevans@freebsd.org>
> Signed-off-by: Warner Losh <imp@bsdimp.com>
> ---
>  bsd-user/qemu.h   |  3 ++
>  bsd-user/signal.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 92 insertions(+)
>
> diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
> index e12617f5d69..e8c417c7c33 100644
> --- a/bsd-user/qemu.h
> +++ b/bsd-user/qemu.h
> @@ -223,7 +223,10 @@ void queue_signal(CPUArchState *env, int sig, 
> target_siginfo_t *info);
>  abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong 
> sp);
>  int target_to_host_signal(int sig);
>  int host_to_target_signal(int sig);
> +void host_to_target_sigset(target_sigset_t *d, const sigset_t *s);
> +void target_to_host_sigset(sigset_t *d, const target_sigset_t *s);
>  void QEMU_NORETURN force_sig(int target_sig);
> +int qemu_sigorset(sigset_t *dest, const sigset_t *left, const sigset_t 
> *right);
>
>  /* mmap.c */
>  int target_mprotect(abi_ulong start, abi_ulong len, int prot);
> diff --git a/bsd-user/signal.c b/bsd-user/signal.c
> index 93c3b3c5033..8dadc9a39a7 100644
> --- a/bsd-user/signal.c
> +++ b/bsd-user/signal.c
> @@ -32,6 +32,9 @@
>
>  static struct target_sigaction sigact_table[TARGET_NSIG];
>  static void host_signal_handler(int host_sig, siginfo_t *info, void *puc);
> +static void target_to_host_sigset_internal(sigset_t *d,
> +        const target_sigset_t *s);
> +
>
>  int host_to_target_signal(int sig)
>  {
> @@ -43,6 +46,44 @@ int target_to_host_signal(int sig)
>      return sig;
>  }
>
> +static inline void target_sigemptyset(target_sigset_t *set)
> +{
> +    memset(set, 0, sizeof(*set));
> +}
> +
> +#include <signal.h>

Don't include system headers halfway through the file like this,
please : put the #include at the top of the file with the others.

> +
> +int
> +qemu_sigorset(sigset_t *dest, const sigset_t *left, const sigset_t *right)
> +{
> +    sigset_t work;
> +    int i;
> +
> +    sigemptyset(&work);
> +    for (i = 1; i < NSIG; ++i) {
> +        if (sigismember(left, i) || sigismember(right, i)) {
> +            sigaddset(&work, i);
> +        }
> +    }
> +
> +    *dest = work;
> +    return 0;
> +}

FreeBSD's manpage says it has a native sigorset() --
https://www.freebsd.org/cgi/man.cgi?query=sigemptyset&sektion=3&apropos=0&manpath=freebsd
can you just use that ?

> +
> +static inline void target_sigaddset(target_sigset_t *set, int signum)
> +{
> +    signum--;
> +    uint32_t mask = (uint32_t)1 << (signum % TARGET_NSIG_BPW);
> +    set->__bits[signum / TARGET_NSIG_BPW] |= mask;
> +}
> +
> +static inline int target_sigismember(const target_sigset_t *set, int signum)
> +{
> +    signum--;
> +    abi_ulong mask = (abi_ulong)1 << (signum % TARGET_NSIG_BPW);
> +    return (set->__bits[signum / TARGET_NSIG_BPW] & mask) != 0;
> +}
> +
>  /* Adjust the signal context to rewind out of safe-syscall if we're in it */
>  static inline void rewind_if_in_safe_syscall(void *puc)
>  {
> @@ -55,6 +96,54 @@ static inline void rewind_if_in_safe_syscall(void *puc)
>      }
>  }
>
> +static void host_to_target_sigset_internal(target_sigset_t *d,
> +        const sigset_t *s)
> +{
> +    int i;
> +
> +    target_sigemptyset(d);
> +    for (i = 1; i <= TARGET_NSIG; i++) {

i here is iterating through host signal numbers, not target
numbers, so TARGET_NSIG isn't the right upper bound.
On Linux we iterate from 1 to _NSIG-1; on BSD I think
you may want (i = 0; i < NSIG; i++), but you should check that.

> +        if (sigismember(s, i)) {
> +            target_sigaddset(d, host_to_target_signal(i));
> +        }
> +    }
> +}

These functions are a little odd when you compare them to their
linux-user equivalents, because they're both written
with a sort of abstraction between host and target signal
numbers (they call host_to_target_signal() and
target_to_host_signal()) but also written with baked-in
assumptions that the mapping is basically 1:1 (they don't
have the code that handles the possibility that the
target signal isn't representable as a host signal or
vice-versa). But assuming the BSDs don't change their
signal numbering across architectures, this is fine.

thanks
-- PMM