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cde/src/lib/libast/comp/spawnveg.c
Johnothan King 0863a8eb29 Support glibc 2.35's posix_spawn_file_actions_addtcsetpgrp_np(3) 
This commit implements support for the glibc 2.35
posix_spawn_file_actions_addtcsetpgrp_np(3) extension[2][3],
updating spawnveg(3) to use the new function for setting the
terminal group. This was done with the intention of improving
performance in interactive shells without reintroducing previous
race conditions[4][5].

[1]: https://sourceware.org/pipermail/libc-alpha/2022-February/136040.html
[2]: https://sourceware.org/git/?p=glibc.git;a=commit;h=342cc934
[3]: https://sourceware.org/git/?p=glibc.git;a=commit;h=6289d28d
[4]: https://github.com/ksh93/ksh/issues/79
[5]: https://www.mail-archive.com/ast-developers@research.att.com/msg00717.html

src/cmd/ksh93/sh/path.c:
- Tell spawnveg(3) to set the terminal process group when launching
  a child process in an interactive shell.

src/cmd/ksh93/sh/xec.c:
- If posix_spawn_file_actions_addtcsetpgrp_np(3) is available,
  allow use of spawnveg(3) (via sh_ntfork()) even with job control
  active.
- sh_ntfork(): Reimplement most of the SIGTSTP handling code
  removed in commit 66c37202.

src/lib/libast/comp/spawnveg.c,
src/lib/libast/misc/procopen.c,
src/lib/libast/features/sys:
- Add support for posix_spawn_file_actions_addtcsetpgrp_np(3).
- Allow spawnveg to set the terminal process group when pgid == 0.
  This was necessary to avoid race conditions when using the new
  function.

src/lib/libast/features/lib:
- Detect posix_spawn_file_actions_addtcsetpgrp_np(3).
- Do not detect an OS spawnveg(3). With the API changes to spawnveg
  in this pull request ksh probably can't use the OS's spawnveg
  function anymore. (That's assuming anything else even provides a
  spawnveg function to begin with, which is unlikely.)

src/lib/libast/features/api,
src/cmd/ksh93/include/defs.h:
- Bump libast version (20220101 => 20220201) due to the spawnveg(3)
  API change.

src/lib/libast/man/spawnveg.3:
- Document the changes to spawnveg(3) in the corresponding man
  page. Currently, it will only use the new tcfd argument if
  posix_spawn_file_actions_addtcsetpgrp_np(3) is supported. This
  could also be implemented for the fork(2) fallback, but for now
  I've avoided changing that since actually using it in the fork
  code would likely require a lot of hackery to avoid attempting
  tcsetpgrp with vfork (the behavior of tcsetpgrp after vfork is
  not portable) and would only benefit systems that don't have
  posix_spawn and vfork (I can't recall any off the top of my head
  that would fall under that category).
- Updated the man page to account for spawnveg's change in
  behavior.

Co-authored-by: Martijn Dekker <martijn@inlv.org>
2022-02-05 13:31:31 +00:00

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/***********************************************************************
* *
* This software is part of the ast package *
* Copyright (c) 1985-2012 AT&T Intellectual Property *
* Copyright (c) 2020-2022 Contributors to ksh 93u+m *
* and is licensed under the *
* Eclipse Public License, Version 1.0 *
* by AT&T Intellectual Property *
* *
* A copy of the License is available at *
* http://www.eclipse.org/org/documents/epl-v10.html *
* (with md5 checksum b35adb5213ca9657e911e9befb180842) *
* *
* Information and Software Systems Research *
* AT&T Research *
* Florham Park NJ *
* *
* Glenn Fowler <gsf@research.att.com> *
* David Korn <dgk@research.att.com> *
* Phong Vo <kpv@research.att.com> *
* *
***********************************************************************/
/*
* spawnveg -- spawnve with process group or session control
*
* pgid <0 setsid() [session group leader]
* 0 nothing [retain session and process group]
* 1 setpgid(0,0) [process group leader]
* >1 setpgid(0,pgid) [join process group]
*/
#include <ast.h>
#if _lib_posix_spawn > 1 /* reports underlying exec() errors */
#include <spawn.h>
#include <error.h>
#include <wait.h>
pid_t
spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid, int tcfd)
{
int err, flags = 0;
pid_t pid;
posix_spawnattr_t attr;
#if _lib_posix_spawn_file_actions_addtcsetpgrp_np
posix_spawn_file_actions_t actions;
#endif
if (err = posix_spawnattr_init(&attr))
goto nope;
#if POSIX_SPAWN_SETSID
if (pgid == -1)
flags |= POSIX_SPAWN_SETSID;
#endif
if (pgid && pgid != -1)
flags |= POSIX_SPAWN_SETPGROUP;
if (flags && (err = posix_spawnattr_setflags(&attr, flags)))
goto bad;
if (pgid && pgid != -1)
{
if (pgid <= 1)
pgid = 0;
if (err = posix_spawnattr_setpgroup(&attr, pgid))
goto bad;
}
#if _lib_posix_spawn_file_actions_addtcsetpgrp_np
if (tcfd >= 0)
{
if (err = posix_spawn_file_actions_init(&actions))
goto bad;
if (err = posix_spawn_file_actions_addtcsetpgrp_np(&actions, tcfd))
goto fail;
}
if (err = posix_spawn(&pid, path, (tcfd >= 0) ? &actions : NiL, &attr, argv, envv ? envv : environ))
#else
if (err = posix_spawn(&pid, path, NiL, &attr, argv, envv ? envv : environ))
#endif
{
if ((err != EPERM) || (err = posix_spawn(&pid, path, NiL, NiL, argv, envv ? envv : environ)))
goto fail;
}
#if _lib_posix_spawn_file_actions_addtcsetpgrp_np
if (tcfd >= 0)
posix_spawn_file_actions_destroy(&actions);
#endif
posix_spawnattr_destroy(&attr);
return pid;
fail:
#if _lib_posix_spawn_file_actions_addtcsetpgrp_np
if (tcfd >= 0)
posix_spawn_file_actions_destroy(&actions);
#endif
bad:
posix_spawnattr_destroy(&attr);
nope:
errno = err;
return -1;
}
#else
#if _lib_spawn_mode
#include <process.h>
#ifndef P_NOWAIT
#define P_NOWAIT _P_NOWAIT
#endif
#if !defined(P_DETACH) && defined(_P_DETACH)
#define P_DETACH _P_DETACH
#endif
pid_t
spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid, int tcfd)
{
NOT_USED(tcfd);
#if defined(P_DETACH)
return spawnve(pgid ? P_DETACH : P_NOWAIT, path, argv, envv ? envv : environ);
#else
return spawnve(P_NOWAIT, path, argv, envv ? envv : environ);
#endif
}
#else
#if _lib_spawn && _hdr_spawn && _mem_pgroup_inheritance
#include <spawn.h>
/*
* MVS OpenEdition / z/OS fork+exec+(setpgid)
*/
pid_t
spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid, int tcfd)
{
struct inheritance inherit;
NOT_USED(tcfd);
inherit.flags = 0;
if (pgid)
{
inherit.flags |= SPAWN_SETGROUP;
inherit.pgroup = (pgid > 1) ? pgid : SPAWN_NEWPGROUP;
}
return spawn(path, 0, (int*)0, &inherit, (const char**)argv, (const char**)envv);
}
#else
#include <error.h>
#include <wait.h>
#include <sig.h>
#include <ast_tty.h>
#include <ast_vfork.h>
#if _lib_spawnve && _hdr_process
#include <process.h>
#if defined(P_NOWAIT) || defined(_P_NOWAIT)
#undef _lib_spawnve
#endif
#endif
#if !_lib_vfork
#undef _real_vfork
#endif
/*
* fork+exec+(setsid|setpgid)
*/
pid_t
spawnveg(const char* path, char* const argv[], char* const envv[], pid_t pgid, int tcfd)
{
#if _lib_fork || _lib_vfork
int n;
int m;
pid_t pid;
pid_t rid;
#if _real_vfork
volatile int exec_errno;
volatile int* volatile exec_errno_ptr;
#else
int err[2];
#endif
#endif
NOT_USED(tcfd);
if (!envv)
envv = environ;
#if _lib_spawnve
#if _lib_fork || _lib_vfork
if (!pgid)
#endif
return spawnve(path, argv, envv);
#endif
#if _lib_fork || _lib_vfork
n = errno;
#if _real_vfork
exec_errno = 0;
exec_errno_ptr = &exec_errno;
#else
if (pipe(err) < 0)
err[0] = -1;
else
{
fcntl(err[0], F_SETFD, FD_CLOEXEC);
fcntl(err[1], F_SETFD, FD_CLOEXEC);
}
#endif
sigcritical(SIG_REG_EXEC|SIG_REG_PROC);
#if _lib_vfork
pid = vfork();
#else
pid = fork();
#endif
if (pid == -1)
n = errno;
else if (!pid)
{
sigcritical(0);
if (pgid == -1)
setsid();
else if (pgid)
{
m = 0;
if (pgid == 1 || pgid == -2 && (m = 1))
pgid = getpid();
if (setpgid(0, pgid) < 0 && errno == EPERM)
setpgid(pgid, 0);
#if _lib_tcgetpgrp
if (m)
tcsetpgrp(2, pgid);
#elif defined(TIOCSPGRP)
if (m)
ioctl(2, TIOCSPGRP, &pgid);
#endif
}
execve(path, argv, envv);
#if _real_vfork
*exec_errno_ptr = errno;
#else
if (err[0] != -1)
{
m = errno;
write(err[1], &m, sizeof(m));
}
#endif
_exit(errno == ENOENT ? EXIT_NOTFOUND : EXIT_NOEXEC);
}
rid = pid;
#if _real_vfork
if (pid != -1 && (m = *exec_errno_ptr))
{
while (waitpid(pid, NiL, 0) == -1 && errno == EINTR);
rid = pid = -1;
n = m;
}
#else
if (err[0] != -1)
{
close(err[1]);
if (pid != -1)
{
m = 0;
while (read(err[0], &m, sizeof(m)) == -1)
if (errno != EINTR)
{
m = errno;
break;
}
if (m)
{
while (waitpid(pid, &n, 0) && errno == EINTR);
rid = pid = -1;
n = m;
}
}
close(err[0]);
}
#endif
sigcritical(0);
if (pid != -1 && pgid > 0)
{
/*
* parent and child are in a race here
*/
if (pgid == 1)
pgid = pid;
if (setpgid(pid, pgid) < 0 && pid != pgid && errno == EPERM)
setpgid(pid, pid);
}
errno = n;
return rid;
#else
errno = ENOSYS;
return -1;
#endif
}
#endif
#endif
#endif
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