diff options
Diffstat (limited to 'src/libstddjb/child_spawn.c')
| -rw-r--r-- | src/libstddjb/child_spawn.c | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/src/libstddjb/child_spawn.c b/src/libstddjb/child_spawn.c new file mode 100644 index 0000000..aa937fd --- /dev/null +++ b/src/libstddjb/child_spawn.c @@ -0,0 +1,228 @@ +/* ISC license. */ + +/* MT-unsafe */ + +#include <skalibs/sysdeps.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <sys/wait.h> +#include <unistd.h> +#include <errno.h> +#include <signal.h> +#include <skalibs/allreadwrite.h> +#include <skalibs/bytestr.h> +#include <skalibs/env.h> +#include <skalibs/djbunix.h> +#include <skalibs/uint.h> +#include <skalibs/webipc.h> + +#ifdef SKALIBS_HASPOSIXSPAWN + +#include <stdlib.h> +#include <spawn.h> +#include <skalibs/config.h> + +#else + +#include <skalibs/sig.h> +#include <skalibs/strerr2.h> + +#endif + +#define NOFDVAR "SKALIBS_CHILD_SPAWN_FDS" + + + /* + If n = 0 : child's stdin and stdout are the same as the parent's + If n = 1 : Unix socket between parent and child. + Additional canals, if needed, may be fd-passed through it. + If n >= 2 : pipes between parent and child. + Parent reads on even ones, writes on odd ones. + */ + +pid_t child_spawn (char const *prog, char const *const *argv, char const *const *envp, int *fds, unsigned int n) +{ +#ifdef SKALIBS_HASPOSIXSPAWN + posix_spawn_file_actions_t actions ; + posix_spawnattr_t attr ; +#endif + int p[n ? n : 1][2] ; + int syncpipe[2] ; + pid_t pid ; + int e ; + unsigned int m = sizeof(NOFDVAR) ; + unsigned int i ; + char modifs[m + 1 + n * UINT_FMT] ; + byte_copy(modifs, sizeof(NOFDVAR), NOFDVAR "=") ; + if (n == 1) + { + if (ipc_pair_b(p[0]) < 0) return 0 ; + } + else if (n >= 2) + { + for (i = 0 ; i < n ; i++) if (pipe(p[i]) < 0) { e = errno ; goto errp ; } + } + if (pipe(syncpipe) < 0) { e = errno ; goto errp ; } + if (coe(syncpipe[1]) < 0) { e = errno ; goto errsp ; } + for (i = 0 ; i < n ; i++) + if ((ndelay_on(p[i][i & 1]) < 0) || (coe(p[i][i & 1]) < 0)) + { + e = errno ; goto errsp ; + } + for (i = 2 ; i < n ; i++) + { + m += uint_fmt(modifs + m, p[i][!(i & 1)]) ; + if (i+1 < n) modifs[m++] = ',' ; + } + modifs[m++] = 0 ; + +#ifdef SKALIBS_HASPOSIXSPAWN + + e = posix_spawnattr_init(&attr) ; + if (e) goto errsp ; + { + sigset_t set ; + sigemptyset(&set) ; + e = posix_spawnattr_setsigmask(&attr, &set) ; + } + if (e) goto errattr ; + e = posix_spawn_file_actions_init(&actions) ; + if (e) goto errattr ; + e = posix_spawn_file_actions_addclose(&actions, syncpipe[0]) ; + if (e) goto erractions ; + switch (n) + { + case 0 : + break ; + case 1 : + e = posix_spawn_file_actions_adddup2(&actions, p[0][1], 1) ; + if (e) goto erractions ; + e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ; + if (e) goto erractions ; + e = posix_spawn_file_actions_adddup2(&actions, 1, 0) ; + if (e) goto erractions ; + break ; + default : + e = posix_spawn_file_actions_adddup2(&actions, p[1][0], 0) ; + if (e) goto erractions ; + e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ; + if (e) goto erractions ; + e = posix_spawn_file_actions_adddup2(&actions, p[0][1], 1) ; + if (e) goto erractions ; + e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ; + if (e) goto erractions ; + break ; + } + { + int haspath = !!env_get("PATH") ; + unsigned int envlen = env_len(envp) ; + char const *newenv[envlen + 2] ; + if (!env_merge(newenv, envlen+2, envp, envlen, modifs, m)) goto errsp ; + if (!haspath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0)) + { + e = errno ; goto erractions ; + } + e = posix_spawnp(&pid, prog, &actions, &attr, (char *const *)argv, (char *const *)newenv) ; + if (!haspath) unsetenv("PATH") ; + if (e) goto erractions ; + } + + posix_spawn_file_actions_destroy(&actions) ; + posix_spawnattr_destroy(&attr) ; + +#else + + pid = fork() ; + if (pid < 0) { e = errno ; goto errsp ; } + else if (!pid) + { + unsigned int len = str_len(PROG) ; + char name[len + 9] ; + byte_copy(name, len, PROG) ; + byte_copy(name + len, 9, " (child)") ; + PROG = name ; + fd_close(syncpipe[0]) ; + switch (n) + { + case 0 : + { + int fd = open2("/dev/null", O_RDONLY) ; + if (fd < 0) goto syncdie ; + if (fd_move(0, fd) < 0) goto syncdie ; + fd = open2("/dev/null", O_WRONLY) ; + if (fd < 0) goto syncdie ; + if (fd_move(1, fd) < 0) goto syncdie ; + break ; + } + case 1 : + if (fd_move(1, p[0][1]) < 0) goto syncdie ; + if (fd_copy(0, 1) < 0) goto syncdie ; + break ; + default : + if (fd_move2(0, p[1][0], 1, p[0][1]) < 0) goto syncdie ; + break ; + } + sig_blocknone() ; + pathexec_r_name(prog, argv, envp, env_len(envp), modifs, m) ; + + syncdie: + { + char c = errno ; + fd_write(syncpipe[1], &c, 1) ; + } + _exit(127) ; + } + +#endif + + fd_close(syncpipe[1]) ; + { + char c ; + syncpipe[1] = fd_read(syncpipe[0], &c, 1) ; + if (syncpipe[1]) + { + if (syncpipe[1] < 0) e = errno ; + else + { + kill(pid, SIGKILL) ; + e = c ; + } + wait_pid(pid, &syncpipe[1]) ; + goto errsp0 ; + } + } + if (waitpid_nointr(pid, &e, WNOHANG)) + { + e = WEXITSTATUS(e) == 127 ? EIO : 0 ; + goto errsp0 ; + } + + fd_close(syncpipe[0]) ; + for (i = n ; i ; i--) + { + fd_close(p[i-1][i & 1]) ; + fds[i-1] = p[i-1][!(i & 1)] ; + } + return pid ; + +#ifdef SKALIBS_HASPOSIXSPAWN + erractions: + posix_spawn_file_actions_destroy(&actions) ; + errattr: + posix_spawnattr_destroy(&attr) ; +#endif + errsp: + fd_close(syncpipe[1]) ; + errsp0: + fd_close(syncpipe[0]) ; + i = n ; + errp: + while (i--) + { + fd_close(p[i][1]) ; + fd_close(p[i][0]) ; + } + errno = e ; + return 0 ; +} |