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

[Warner Losh <imp@bsdimp.com>]

[-- Attachment #1: Type: text/plain, Size: 5300 bytes --]

On Fri, Jan 14, 2022 at 4:14 AM Peter Maydell <peter.maydell@linaro.org>
wrote:

> 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.
>

Yea, this isn't even needed, so I just removed it.


> > +
> > +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 ?
>

Yes.


> > +
> > +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.
>

You're correct. The values are the same, but logically NSIG is more correct.


> > +        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.
>

I can assume that, at least for now, so I've just added a comment
about that.

Warner

[-- Attachment #2: Type: text/html, Size: 7412 bytes --]