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[subprocs] use posix_spawn in place of fork+exec #2194

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nick black 2021-09-26 05:58:16 -04:00 committed by nick black
parent 9d7fb54535
commit 8585c0a8a9
1 changed files with 55 additions and 37 deletions
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92
src/lib/fd.c
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@ -8,6 +8,8 @@
#endif
#ifdef __MINGW64__
#include <winsock2.h>
#else
#include <spawn.h>
#endif
#if (defined(__linux__))
#include <linux/wait.h>
@ -142,6 +144,7 @@ int ncfdplane_destroy(ncfdplane* n){
return ret;
}
#ifndef __MINGW64__
// get 2 pipes, and ensure they're both set to close-on-exec
static int
lay_pipes(int pipes[static 2]){
@ -168,45 +171,67 @@ lay_pipes(int pipes[static 2]){
// ncfdplane around the read end, involving creation of a new thread. the
// parent then returns.
static pid_t
launch_pipe_process(int* pipefd, int* pidfd){
#ifndef __MINGW64__
launch_pipe_process(int* pipefd, int* pidfd, unsigned usepath,
const char* bin, char* const arg[], char* const env[]){
*pidfd = -1;
int pipes[2];
if(lay_pipes(pipes)){
return -1;
}
pid_t p = -1;
// on linux, we try to use the brand-new pidfd capability via clone3(). if
// that fails, fall through to fork(), which is all we try to use on freebsd.
// FIXME clone3 is not yet supported on debian sparc64/alpha as of 2020-07
#ifdef USING_PIDFD
// on linux, we try to use the brand-new pidfd capability via clone3(). if
// that fails, fall through to posix_spawn(), our only option on freebsd.
// FIXME clone3 is not yet supported on debian sparc64/alpha as of 2020-07
struct clone_args clargs;
memset(&clargs, 0, sizeof(clargs));
clargs.pidfd = (uintptr_t)pidfd;
clargs.flags = CLONE_CLEAR_SIGHAND | CLONE_FS | CLONE_PIDFD;
clargs.exit_signal = SIGCHLD;
p = syscall(__NR_clone3, &clargs, sizeof(clargs));
#endif
if(p < 0){
p = fork();
}
if(p == 0){ // child
if(dup2(pipes[1], STDOUT_FILENO) < 0 || dup2(pipes[1], STDERR_FILENO) < 0){
logerror("Couldn't dup() %d (%s)\n", pipes[1], strerror(errno));
exit(EXIT_FAILURE);
}
}else if(p > 0){ // parent
if(env){
execvpe(bin, arg, env);
}else if(usepath){
execvp(bin, arg);
}else{
execv(bin, arg);
}
exit(EXIT_FAILURE);
}else if(p < 0){
logwarn("clone3() failed (%s), using posix_spawn()\n", strerror(errno));
}
#endif
if(p < 0){
posix_spawn_file_actions_t factions;
if(posix_spawn_file_actions_init(&factions)){
logerror("couldn't initialize spawn file actions\n");
return -1;
}
posix_spawn_file_actions_adddup2(&factions, pipes[1], STDOUT_FILENO);
posix_spawn_file_actions_adddup2(&factions, pipes[1], STDERR_FILENO);
int r;
if(usepath){
r = posix_spawnp(&p, bin, &factions, NULL, arg, env);
}else{
r = posix_spawn(&p, bin, &factions, NULL, arg, env);
}
if(r){
logerror("posix_spawn %s failed (%s)\n", bin, strerror(errno));
}
posix_spawn_file_actions_destroy(&factions);
}
if(p > 0){ // parent
*pipefd = pipes[0];
set_fd_nonblocking(*pipefd, 1, NULL);
}
return p;
#else
// FIXME use CreateProcess()
(void)pipefd;
(void)pidfd;
return -1;
#endif
}
#endif
// nuke the just-spawned process, and reap it. called before the subprocess
// reader thread is launched (which otherwise reaps the subprocess).
@ -326,33 +351,15 @@ ncexecvpe(ncplane* n, const ncsubproc_options* opts, unsigned usepath,
if(opts->flags > 0){
logwarn("Provided unsupported flags %016jx\n", (uintmax_t)opts->flags);
}
#ifndef __MINGW64__
int fd = -1;
ncsubproc* ret = malloc(sizeof(*ret));
if(ret == NULL){
return NULL;
}
memset(ret, 0, sizeof(*ret));
ret->pid = launch_pipe_process(&fd, &ret->pidfd);
if(ret->pid == 0){
if(env){
#ifdef __linux__
execvpe(bin, arg, env);
#elif defined(__APPLE__) || defined(__gnu_hurd__)
(void)env;
execvp(bin, arg); // FIXME env? use posix_spawn()!
#elif defined(__MINGW64__) // use CreateProcess()!
(void)arg;
(void)env;
#else
exect(bin, arg, env);
#endif
}else if(usepath){
execvp(bin, arg);
}else{
execv(bin, arg);
}
exit(EXIT_FAILURE);
}else if(ret->pid < 0){
ret->pid = launch_pipe_process(&fd, &ret->pidfd, usepath, bin, arg, env);
if(ret->pid < 0){
free(ret);
return NULL;
}
@ -362,6 +369,17 @@ ncexecvpe(ncplane* n, const ncsubproc_options* opts, unsigned usepath,
return NULL;
}
return ret;
#else
// FIXME use CreateProcess()
(void)n;
(void)usepath;
(void)bin;
(void)arg;
(void)env;
(void)cbfxn;
(void)donecbfxn;
return NULL;
#endif
}
ncsubproc* ncsubproc_createv(ncplane* n, const ncsubproc_options* opts,