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Re: [PATCH v2] sysdeps/wait: Use the waitid syscall if required


On Fri, Oct 25, 2019 at 6:01 PM Alistair Francis
<alistair.francis@wdc.com> wrote:
>
> If the waitpid and wait4 syscalls aren't avaliable (such as y2038 safe
> 32-bit systems) let us use the waitid syscall isntead.
>
> Unfortunately waitid is substantially differnt to waitpid and wait4, so
> the conversion ends up being complex.
>
> For full support we need the 5.4+ kernel as that allows a pid of 0 with
> the P_PGID idtype.
>
> This change also removes the wait4 syscall from syscalls.list and
> replaces it with a __wait4() implementation.
> ---
> This was patch was runtime tested with RV32 and RV64
> It was build tested using the ./scripts/build-many-glibcs.py script.

Ping!

Alistair

>
>  include/sys/wait.h                         |  3 +-
>  sysdeps/unix/sysv/linux/syscalls.list      |  1 -
>  sysdeps/unix/sysv/linux/wait.c             | 41 +++++++++-
>  sysdeps/unix/sysv/linux/wait4.c            | 87 ++++++++++++++++++++++
>  sysdeps/unix/sysv/linux/waitpid.c          | 59 ++++++++++++++-
>  sysdeps/unix/sysv/linux/waitpid_nocancel.c | 56 +++++++++++++-
>  6 files changed, 239 insertions(+), 8 deletions(-)
>  create mode 100644 sysdeps/unix/sysv/linux/wait4.c
>
> diff --git a/include/sys/wait.h b/include/sys/wait.h
> index 5ac9cd6ca6b..fab0e17f7d5 100644
> --- a/include/sys/wait.h
> +++ b/include/sys/wait.h
> @@ -13,7 +13,6 @@ extern __pid_t __wait (int *__stat_loc);
>  extern __pid_t __wait3 (int *__stat_loc,
>                         int __options, struct rusage * __usage);
>  extern __pid_t __wait4 (__pid_t __pid, int *__stat_loc,
> -                       int __options, struct rusage *__usage)
> -                       attribute_hidden;
> +                       int __options, struct rusage *__usage);
>  #endif
>  #endif
> diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
> index e374f97b5f8..31f1d258fe1 100644
> --- a/sysdeps/unix/sysv/linux/syscalls.list
> +++ b/sysdeps/unix/sysv/linux/syscalls.list
> @@ -69,7 +69,6 @@ swapoff               -       swapoff         i:s     __swapoff       swapoff
>  unshare                EXTRA   unshare         i:i     unshare
>  uselib         EXTRA   uselib          i:s     __compat_uselib uselib@GLIBC_2.0:GLIBC_2.23
>  utime          -       utime           i:sP    utime
> -wait4          -       wait4           i:iWiP  __wait4         wait4
>
>  chown          -       chown           i:sii   __libc_chown    __chown chown
>
> diff --git a/sysdeps/unix/sysv/linux/wait.c b/sysdeps/unix/sysv/linux/wait.c
> index c2385c752e2..28a27af8135 100644
> --- a/sysdeps/unix/sysv/linux/wait.c
> +++ b/sysdeps/unix/sysv/linux/wait.c
> @@ -26,9 +26,44 @@
>  pid_t
>  __libc_wait (int *stat_loc)
>  {
> -  pid_t result = SYSCALL_CANCEL (wait4, WAIT_ANY, stat_loc, 0,
> -                                (struct rusage *) NULL);
> -  return result;
> +#ifdef __NR_wait4
> +  return SYSCALL_CANCEL (wait4, WAIT_ANY, stat_loc, 0,
> +                         (struct rusage *) NULL);
> +#else
> +  siginfo_t infop;
> +  __pid_t ret;
> +
> +  ret = SYSCALL_CANCEL (waitid, P_ALL, 0, &infop, WEXITED, NULL);
> +
> +  if (ret < 0)
> +      return ret;
> +
> +  if (stat_loc)
> +    {
> +      *stat_loc = 0;
> +      switch (infop.si_code)
> +      {
> +        case CLD_EXITED:
> +            *stat_loc = infop.si_status << 8;
> +            break;
> +        case CLD_DUMPED:
> +            *stat_loc = 0x80;
> +            /* Fallthrough */
> +        case CLD_KILLED:
> +            *stat_loc |= infop.si_status;
> +            break;
> +        case CLD_TRAPPED:
> +        case CLD_STOPPED:
> +            *stat_loc = infop.si_status << 8 | 0x7f;
> +            break;
> +        case CLD_CONTINUED:
> +            *stat_loc = 0xffff;
> +            break;
> +      }
> +    }
> +
> +  return infop.si_pid;
> +#endif
>  }
>
>  weak_alias (__libc_wait, __wait)
> diff --git a/sysdeps/unix/sysv/linux/wait4.c b/sysdeps/unix/sysv/linux/wait4.c
> new file mode 100644
> index 00000000000..6d6fea34f9a
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/wait4.c
> @@ -0,0 +1,87 @@
> +/* Linux wait4 syscall implementation.
> +   Copyright (C) 1991-2019 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sys/wait.h>
> +#include <errno.h>
> +#include <sys/resource.h>
> +#include <stddef.h>
> +
> +__pid_t
> +__wait4 (__pid_t pid, int *stat_loc, int options,
> +         struct rusage *usage)
> +{
> +#ifdef __NR_wait4
> +  return INLINE_SYSCALL_CALL (wait4, pid, stat_loc, options, usage);
> +#else
> +  __pid_t ret;
> +  idtype_t idtype = P_PID;
> +  siginfo_t infop;
> +
> +  if (pid < -1)
> +    {
> +      idtype = P_PGID;
> +      pid *= -1;
> +    }
> +  else if (pid == -1)
> +    {
> +      idtype = P_ALL;
> +    }
> +  else if (pid == 0)
> +    {
> +      /* Linux Kernels 5.4+ support pid 0 with P_PGID to specify wait on
> +       * the current PID's group. Earlier kernels will return -EINVAL.
> +       */
> +      idtype = P_PGID;
> +    }
> +
> +  options |= WEXITED;
> +
> +  ret = INLINE_SYSCALL_CALL (waitid, idtype, pid, &infop, options, usage);
> +
> +  if (ret < 0)
> +      return ret;
> +
> +  if (stat_loc)
> +    {
> +      *stat_loc = 0;
> +      switch (infop.si_code)
> +      {
> +        case CLD_EXITED:
> +            *stat_loc = infop.si_status << 8;
> +            break;
> +        case CLD_DUMPED:
> +            *stat_loc = 0x80;
> +            /* Fallthrough */
> +        case CLD_KILLED:
> +            *stat_loc |= infop.si_status;
> +            break;
> +        case CLD_TRAPPED:
> +        case CLD_STOPPED:
> +            *stat_loc = infop.si_status << 8 | 0x7f;
> +            break;
> +        case CLD_CONTINUED:
> +            *stat_loc = 0xffff;
> +            break;
> +      }
> +    }
> +
> +  return infop.si_pid;
> +#endif
> +}
> +
> +weak_alias (__wait4, wait4)
> diff --git a/sysdeps/unix/sysv/linux/waitpid.c b/sysdeps/unix/sysv/linux/waitpid.c
> index d35aac01bcc..a02275c3ff5 100644
> --- a/sysdeps/unix/sysv/linux/waitpid.c
> +++ b/sysdeps/unix/sysv/linux/waitpid.c
> @@ -20,14 +20,71 @@
>  #include <sysdep-cancel.h>
>  #include <stdlib.h>
>  #include <sys/wait.h>
> +#include <unistd.h>
>
>  __pid_t
>  __waitpid (__pid_t pid, int *stat_loc, int options)
>  {
>  #ifdef __NR_waitpid
>    return SYSCALL_CANCEL (waitpid, pid, stat_loc, options);
> -#else
> +#elif defined(__NR_wait4)
>    return SYSCALL_CANCEL (wait4, pid, stat_loc, options, NULL);
> +#else
> +  __pid_t ret;
> +  idtype_t idtype = P_PID;
> +  siginfo_t infop;
> +
> +  if (pid < -1)
> +    {
> +      idtype = P_PGID;
> +      pid *= -1;
> +    }
> +  else if (pid == -1)
> +    {
> +      idtype = P_ALL;
> +    }
> +  else if (pid == 0)
> +    {
> +      /* Linux Kernels 5.4+ support pid 0 with P_PGID to specify wait on
> +       * the current PID's group. Earlier kernels will return -EINVAL.
> +       */
> +      idtype = P_PGID;
> +    }
> +
> +  options |= WEXITED;
> +
> +  ret = SYSCALL_CANCEL (waitid, idtype, pid, &infop, options, NULL);
> +
> +  if (ret < 0)
> +    {
> +      return ret;
> +    }
> +
> +  if (stat_loc)
> +    {
> +      *stat_loc = 0;
> +      switch (infop.si_code)
> +        {
> +        case CLD_EXITED:
> +            *stat_loc = infop.si_status << 8;
> +            break;
> +        case CLD_DUMPED:
> +            *stat_loc = 0x80;
> +            /* Fallthrough */
> +        case CLD_KILLED:
> +            *stat_loc |= infop.si_status;
> +            break;
> +        case CLD_TRAPPED:
> +        case CLD_STOPPED:
> +            *stat_loc = infop.si_status << 8 | 0x7f;
> +            break;
> +        case CLD_CONTINUED:
> +            *stat_loc = 0xffff;
> +            break;
> +        }
> +    }
> +
> +  return infop.si_pid;
>  #endif
>  }
>  libc_hidden_def (__waitpid)
> diff --git a/sysdeps/unix/sysv/linux/waitpid_nocancel.c b/sysdeps/unix/sysv/linux/waitpid_nocancel.c
> index 3697c6b938c..59b07c5f73d 100644
> --- a/sysdeps/unix/sysv/linux/waitpid_nocancel.c
> +++ b/sysdeps/unix/sysv/linux/waitpid_nocancel.c
> @@ -27,8 +27,62 @@ __waitpid_nocancel (__pid_t pid, int *stat_loc, int options)
>  {
>  #ifdef __NR_waitpid
>    return INLINE_SYSCALL_CALL (waitpid, pid, stat_loc, options);
> -#else
> +#elif defined (__NR_wait4)
>    return INLINE_SYSCALL_CALL (wait4, pid, stat_loc, options, NULL);
> +#else
> +  __pid_t ret;
> +  idtype_t idtype = P_PID;
> +  siginfo_t infop;
> +
> +  if (pid < -1)
> +    {
> +      idtype = P_PGID;
> +      pid *= -1;
> +    }
> +  else if (pid == -1)
> +    {
> +      idtype = P_ALL;
> +    }
> +  else if (pid == 0)
> +    {
> +      /* Linux Kernels 5.4+ support pid 0 with P_PGID to specify wait on
> +       * the current PID's group. Earlier kernels will return -EINVAL.
> +       */
> +      idtype = P_PGID;
> +    }
> +
> +  options |= WEXITED;
> +
> +  ret = INLINE_SYSCALL_CALL (waitid, idtype, pid, &infop, options, NULL);
> +
> +  if (ret < 0)
> +      return ret;
> +
> +  if (stat_loc)
> +    {
> +      *stat_loc = 0;
> +      switch (infop.si_code)
> +        {
> +        case CLD_EXITED:
> +            *stat_loc = infop.si_status << 8;
> +            break;
> +        case CLD_DUMPED:
> +            *stat_loc = 0x80;
> +            /* Fallthrough */
> +        case CLD_KILLED:
> +            *stat_loc |= infop.si_status;
> +            break;
> +        case CLD_TRAPPED:
> +        case CLD_STOPPED:
> +            *stat_loc = infop.si_status << 8 | 0x7f;
> +            break;
> +        case CLD_CONTINUED:
> +            *stat_loc = 0xffff;
> +            break;
> +        }
> +    }
> +
> +  return infop.si_pid;
>  #endif
>  }
>  libc_hidden_def (__waitpid_nocancel)
> --
> 2.23.0
>


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