cspawn revamp, part 1. Prepare for 2.14.0.0.

Signed-off-by: Laurent Bercot <ska@appnovation.com>

1 files changed, 220 insertions, 0 deletions

diff --git a/src/libstddjb/cspawn.c b/src/libstddjb/cspawn.c
new file mode 100644
index 0000000..4db86e0
--- /dev/null
+++ b/src/libstddjb/cspawn.c
@@ -0,0 +1,220 @@
+/* ISC license. */
+
+#include <skalibs/sysdeps.h>
+
+#include <errno.h>
+
+#include <skalibs/cspawn.h>
+
+#ifdef SKALIBS_HASPOSIXSPAWN
+
+#include <signal.h>
+#include <stdlib.h>
+#include <spawn.h>
+
+#include <skalibs/config.h>
+#include <skalibs/djbunix.h>
+
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+
+#include <sys/wait.h>
+
+#include <skalibs/allreadwrite.h>
+
+static inline pid_t cspawn_workaround (pid_t pid, int const *p)
+{
+  siginfo_t si ;
+  int e ;
+  ssize_t r ;
+  char c ;
+
+  fd_close(p[1]) ;
+  r = fd_read(p[0], &c, 1) ;
+  fd_close(p[0]) ;
+  if (r == -1) return 0 ;
+  if (r) return (errno = EILSEQ, 0) ;  /* child wrote, wtf */
+
+  do e = waitid(P_PID, pid, &si, WEXITED | WNOHANG | WNOWAIT) ;
+  while (e == -1 && errno == EINTR) ;
+  if (e == -1) return pid ;  /* we're in trouble, but don't leak a child */
+  if (!si.si_pid) return pid ;  /* child is running */
+  if (si.si_code != CLD_EXITED || si.si_status != 127) return pid ; /* child died after execve(), let caller handle it */
+  /*
+    child exited 127, so either execve() failed, which is what we want to catch,
+    or it raced like a mofo, execve()d and then exited 127 on its own, in which
+    case, tough luck, it never existed.
+  */
+  wait_pid(pid, 0) ;
+  return (errno = 0, 0) ;
+}
+
+#endif
+
+pid_t cspawn (char const *prog, char const *const *argv, char const *const *envp, uint32_t flags, cspawn_fileaction const *fa, size_t n)
+{
+  pid_t pid ;
+  posix_spawnattr_t attr ;
+  posix_spawn_file_actions_t actions ;
+  int e ;
+  int nopath = !getenv("PATH") ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  int p[2] ;
+  if (pipecoe(p) == -1) return 0 ;
+#endif
+
+  if (flags)
+  {
+    e = posix_spawnattr_init(&attr) ;
+    if (e) goto err ;
+    if (flags & 3)
+    {
+      sigset_t set ;
+      sigemptyset(&set) ;
+      e = posix_spawnattr_setsigmask(&attr, &set) ;
+      if (e) goto errattr ;
+      e = posix_spawnattr_setflags(&attr, POSIX_SPAWN_SETSIGMASK) ;
+      if (e) goto errattr ;
+    }
+  }
+
+  if (n)
+  {
+    e = posix_spawn_file_actions_init(&actions) ;
+    if (e) goto errattr ;
+    for (size_t i = 0 ; i < n ; i++)
+    {
+      switch (fa[i].type)
+      {
+        case CSPAWN_FA_CLOSE :
+          e = posix_spawn_file_actions_addclose(&actions, fa[i].x.fd) ;
+          if (e) goto erractions ;
+          break ;
+        case CSPAWN_FA_COPY :
+          e = posix_spawn_file_actions_adddup2(&actions, fa[i].x.fd2[1], fa[i].x.fd2[0]) ;
+          if (e) goto erractions ;
+          break ;
+        case CSPAWN_FA_MOVE :
+          e = posix_spawn_file_actions_adddup2(&actions, fa[i].x.fd2[1], fa[i].x.fd2[0]) ;
+          if (e) goto erractions ;
+          if (fa[i].x.fd2[0] != fa[i].x.fd2[1])
+          {
+            e = posix_spawn_file_actions_addclose(&actions, fa[i].x.fd2[1]) ;
+            if (e) goto erractions ;
+          }
+          break ;
+        case CSPAWN_FA_OPEN :
+          e = posix_spawn_file_actions_addopen(&actions, fa[i].x.openinfo.fd, fa[i].x.openinfo.file, fa[i].x.openinfo.oflag, fa[i].x.openinfo.mode) ;
+          if (e) goto erractions ;
+          break ;
+        default :
+          e = EINVAL ;
+          goto erractions ;
+      }
+    }
+  }
+
+  if (nopath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) == -1)) { e = errno ; goto erractions ; }
+  e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)envp) ;
+  if (nopath) unsetenv("PATH") ;
+  if (e) goto errattr ;
+
+  if (n) posix_spawn_file_actions_destroy(&actions) ;
+  if (flags) posix_spawnattr_destroy(&attr) ;
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  return cspawn_workaround(pid, p) ;
+#else
+  return pid ;
+#endif
+
+ erractions:
+  if (n) posix_spawn_file_actions_destroy(&actions) ;
+ errattr:
+  if (flags) posix_spawnattr_destroy(&attr) ;
+ err:
+#ifdef SKALIBS_HASPOSIXSPAWNEARLYRETURN
+  fd_close(p[1]) ;
+  fd_close(p[0]) ;
+#endif
+  errno = e ;
+  return 0 ;
+}
+
+#else
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/sig.h>
+#include <skalibs/selfpipe.h>
+#include <skalibs/exec.h>
+
+static inline void cspawn_child_exec (char const *prog, char const *const *argv, char const *const *envp, uint32_t flags, cspawn_fileaction const *fa, size_t n)
+{
+  for (size_t i = 0 ; i < n ; i++)
+  {
+    switch (fa[i].type)
+    {
+      case CSPAWN_FA_CLOSE : fd_close(fa[i].x.fd) ; break ;
+      case CSPAWN_FA_COPY :
+        if (fd_copy(fa[i].x.fd2[0], fa[i].x.fd2[1]) == -1) return ;
+        break ;
+      case CSPAWN_FA_MOVE :
+        if (fd_move(fa[i].x.fd2[0], fa[i].x.fd2[1]) == -1) return ;
+        break ;
+      case CSPAWN_FA_OPEN :
+      {
+        int fd = open(fa[i].x.openinfo.file, fa[i].x.openinfo.oflag, fa[i].x.openinfo.mode) ;
+        if (fd == -1) return ;
+        if (fd_move(fa[i].x.openinfo.fd, fd) == -1) return ;
+        break ;
+      }
+      default :
+        errno = EINVAL ; return ;
+    }
+  }
+
+  if (flags & CSPAWN_FLAGS_SELFPIPE_FINISH) selfpipe_finish() ;
+  if (flags & CSPAWN_FLAGS_SIGBLOCKNONE) sig_blocknone() ;
+}
+
+pid_t cspawn (char const *prog, char const *const *argv, char const *const *envp, uint32_t flags, cspawn_fileaction const *fa, size_t n)
+{
+  pid_t pid ;
+  int p[2] ;
+  char c ;
+
+  if (pipecoe(p) == -1) return 0 ;
+  pid = fork() ;
+  if (pid == -1)
+  {
+    fd_close(p[1]) ;
+    fd_close(p[0]) ;
+    return 0 ;
+  }
+  if (!pid)
+  {
+    cspawn_child_exec(prog, argv, envp, flags, fa, n) ;
+    c = errno ;
+    fd_write(p[1], &c, 1) ;
+    _exit(127) ;
+  }
+
+  fd_close(p[1]) ;
+  p[1] = fd_read(p[0], &c, 1) ;
+  if (p[1] < 0)
+  {
+    fd_close(p[0]) ;
+    return 0 ;
+  }
+  fd_close(p[0]) ;
+  if (p[1])
+  {
+    wait_pid(pid, &p[0]) ;
+    errno = (unsigned char)c ;
+    return 0 ;
+  }
+  return pid ;
+}
+
+#endif