1 files changed, 552 insertions, 135 deletions

diff --git a/src/xspawn.c b/src/xspawn.c
index 2cabdcc..3fa4e60 100644
--- a/src/xspawn.c
+++ b/src/xspawn.c
@@ -2,27 +2,36 @@
 // SPDX-License-Identifier: 0BSD
 
 #include "xspawn.h"
+
 #include "alloc.h"
+#include "bfs.h"
 #include "bfstd.h"
-#include "config.h"
+#include "diag.h"
 #include "list.h"
+#include "sighook.h"
+
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/resource.h>
 #include <sys/types.h>
-#include <sys/wait.h>
 #include <unistd.h>
 
-#if BFS_USE_PATHS_H
+#if __has_include(<paths.h>)
 #  include <paths.h>
 #endif
 
+#if BFS_POSIX_SPAWN >= 0
+#  include <spawn.h>
+#endif
+
 /**
  * Types of spawn actions.
  */
 enum bfs_spawn_op {
+	BFS_SPAWN_OPEN,
 	BFS_SPAWN_CLOSE,
 	BFS_SPAWN_DUP2,
 	BFS_SPAWN_FCHDIR,
@@ -33,115 +42,509 @@ enum bfs_spawn_op {
  * A spawn action.
  */
 struct bfs_spawn_action {
+	/** The next action in the list. */
 	struct bfs_spawn_action *next;
 
+	/** This action's operation. */
 	enum bfs_spawn_op op;
+	/** The input fd (or -1). */
 	int in_fd;
+	/** The output fd (or -1). */
 	int out_fd;
-	int resource;
-	struct rlimit rlimit;
+
+	/** Operation-specific args. */
+	union {
+		/** BFS_SPAWN_OPEN args. */
+		struct {
+			const char *path;
+			int flags;
+			mode_t mode;
+		};
+
+		/** BFS_SPAWN_SETRLIMIT args. */
+		struct {
+			int resource;
+			struct rlimit rlimit;
+		};
+	};
 };
 
 int bfs_spawn_init(struct bfs_spawn *ctx) {
 	ctx->flags = 0;
 	SLIST_INIT(ctx);
+
+#if BFS_POSIX_SPAWN >= 0
+	if (sysoption(SPAWN) > 0) {
+		ctx->flags |= BFS_SPAWN_USE_POSIX;
+
+		errno = posix_spawn_file_actions_init(&ctx->actions);
+		if (errno != 0) {
+			return -1;
+		}
+
+		errno = posix_spawnattr_init(&ctx->attr);
+		if (errno != 0) {
+			posix_spawn_file_actions_destroy(&ctx->actions);
+			return -1;
+		}
+	}
+#endif
+
 	return 0;
 }
 
+/**
+ * Clear the BFS_SPAWN_USE_POSIX flag and free the attributes.
+ */
+static void bfs_spawn_clear_posix(struct bfs_spawn *ctx) {
+	if (ctx->flags & BFS_SPAWN_USE_POSIX) {
+		ctx->flags &= ~BFS_SPAWN_USE_POSIX;
+
+#if BFS_POSIX_SPAWN >= 0
+		posix_spawnattr_destroy(&ctx->attr);
+		posix_spawn_file_actions_destroy(&ctx->actions);
+#endif
+	}
+}
+
 int bfs_spawn_destroy(struct bfs_spawn *ctx) {
-	while (ctx->head) {
-		free(SLIST_POP(ctx));
+	bfs_spawn_clear_posix(ctx);
+
+	for_slist (struct bfs_spawn_action, action, ctx) {
+		free(action);
 	}
 
 	return 0;
 }
 
-int bfs_spawn_setflags(struct bfs_spawn *ctx, enum bfs_spawn_flags flags) {
-	ctx->flags = flags;
+#if BFS_POSIX_SPAWN >= 0
+/** Set some posix_spawnattr flags. */
+_maybe_unused
+static int bfs_spawn_addflags(struct bfs_spawn *ctx, short flags) {
+	short prev;
+	errno = posix_spawnattr_getflags(&ctx->attr, &prev);
+	if (errno != 0) {
+		return -1;
+	}
+
+	short next = prev | flags;
+	if (next != prev) {
+		errno = posix_spawnattr_setflags(&ctx->attr, next);
+		if (errno != 0) {
+			return -1;
+		}
+	}
+
 	return 0;
 }
+#endif
 
-/** Add a spawn action to the chain. */
-static struct bfs_spawn_action *bfs_spawn_add(struct bfs_spawn *ctx, enum bfs_spawn_op op) {
+/** Allocate a spawn action. */
+static struct bfs_spawn_action *bfs_spawn_action(enum bfs_spawn_op op) {
 	struct bfs_spawn_action *action = ALLOC(struct bfs_spawn_action);
 	if (!action) {
 		return NULL;
 	}
 
-	action->next = NULL;
+	SLIST_ITEM_INIT(action);
 	action->op = op;
 	action->in_fd = -1;
 	action->out_fd = -1;
+	return action;
+}
 
+int bfs_spawn_addopen(struct bfs_spawn *ctx, int fd, const char *path, int flags, mode_t mode) {
+	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_OPEN);
+	if (!action) {
+		return -1;
+	}
+
+#if BFS_POSIX_SPAWN >= 0
+	if (ctx->flags & BFS_SPAWN_USE_POSIX) {
+		errno = posix_spawn_file_actions_addopen(&ctx->actions, fd, path, flags, mode);
+		if (errno != 0) {
+			free(action);
+			return -1;
+		}
+	}
+#endif
+
+	action->out_fd = fd;
+	action->path = path;
+	action->flags = flags;
+	action->mode = mode;
 	SLIST_APPEND(ctx, action);
-	return action;
+	return 0;
 }
 
 int bfs_spawn_addclose(struct bfs_spawn *ctx, int fd) {
-	if (fd < 0) {
-		errno = EBADF;
+	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_CLOSE);
+	if (!action) {
 		return -1;
 	}
 
-	struct bfs_spawn_action *action = bfs_spawn_add(ctx, BFS_SPAWN_CLOSE);
-	if (action) {
-		action->out_fd = fd;
-		return 0;
-	} else {
-		return -1;
+#if BFS_POSIX_SPAWN >= 0
+	if (ctx->flags & BFS_SPAWN_USE_POSIX) {
+		errno = posix_spawn_file_actions_addclose(&ctx->actions, fd);
+		if (errno != 0) {
+			free(action);
+			return -1;
+		}
 	}
+#endif
+
+	action->out_fd = fd;
+	SLIST_APPEND(ctx, action);
+	return 0;
 }
 
 int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) {
-	if (oldfd < 0 || newfd < 0) {
-		errno = EBADF;
+	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_DUP2);
+	if (!action) {
 		return -1;
 	}
 
-	struct bfs_spawn_action *action = bfs_spawn_add(ctx, BFS_SPAWN_DUP2);
-	if (action) {
-		action->in_fd = oldfd;
-		action->out_fd = newfd;
-		return 0;
-	} else {
-		return -1;
+#if BFS_POSIX_SPAWN >= 0
+	if (ctx->flags & BFS_SPAWN_USE_POSIX) {
+		errno = posix_spawn_file_actions_adddup2(&ctx->actions, oldfd, newfd);
+		if (errno != 0) {
+			free(action);
+			return -1;
+		}
 	}
+#endif
+
+	action->in_fd = oldfd;
+	action->out_fd = newfd;
+	SLIST_APPEND(ctx, action);
+	return 0;
 }
 
+/**
+ * https://www.austingroupbugs.net/view.php?id=1208#c4830 says:
+ *
+ *     ... a search of the directories passed as the environment variable
+ *     PATH ..., using the working directory of the child process after all
+ *     file_actions have been performed.
+ *
+ * but macOS and NetBSD resolve the PATH *before* file_actions (because there
+ * posix_spawn() is its own syscall).
+ */
+#define BFS_POSIX_SPAWNP_AFTER_FCHDIR !(__APPLE__ || __NetBSD__)
+
 int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) {
-	if (fd < 0) {
-		errno = EBADF;
+	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_FCHDIR);
+	if (!action) {
 		return -1;
 	}
 
-	struct bfs_spawn_action *action = bfs_spawn_add(ctx, BFS_SPAWN_FCHDIR);
-	if (action) {
-		action->in_fd = fd;
-		return 0;
+#if BFS_HAS_POSIX_SPAWN_ADDFCHDIR
+#  define BFS_POSIX_SPAWN_ADDFCHDIR posix_spawn_file_actions_addfchdir
+#elif BFS_HAS_POSIX_SPAWN_ADDFCHDIR_NP
+#  define BFS_POSIX_SPAWN_ADDFCHDIR posix_spawn_file_actions_addfchdir_np
+#endif
+
+#if BFS_POSIX_SPAWN >= 0 && defined(BFS_POSIX_SPAWN_ADDFCHDIR)
+	if (ctx->flags & BFS_SPAWN_USE_POSIX) {
+		errno = BFS_POSIX_SPAWN_ADDFCHDIR(&ctx->actions, fd);
+		if (errno != 0) {
+			free(action);
+			return -1;
+		}
+	}
+#else
+	bfs_spawn_clear_posix(ctx);
+#endif
+
+	action->in_fd = fd;
+	SLIST_APPEND(ctx, action);
+	return 0;
+}
+
+int bfs_spawn_setrlimit(struct bfs_spawn *ctx, int resource, const struct rlimit *rl) {
+	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_SETRLIMIT);
+	if (!action) {
+		goto fail;
+	}
+
+#ifdef POSIX_SPAWN_SETRLIMIT
+	if (bfs_spawn_addflags(ctx, POSIX_SPAWN_SETRLIMIT) != 0) {
+		goto fail;
+	}
+
+	errno = posix_spawnattr_setrlimit(&ctx->attr, resource, rl);
+	if (errno != 0) {
+		goto fail;
+	}
+#else
+	bfs_spawn_clear_posix(ctx);
+#endif
+
+	action->resource = resource;
+	action->rlimit = *rl;
+	SLIST_APPEND(ctx, action);
+	return 0;
+
+fail:
+	free(action);
+	return -1;
+}
+
+/**
+ * Context for resolving executables in the $PATH.
+ */
+struct bfs_resolver {
+	/** The executable to spawn. */
+	const char *exe;
+	/** The $PATH to resolve in. */
+	char *path;
+	/** A buffer to hold the resolved path. */
+	char *buf;
+	/** The size of the buffer. */
+	size_t len;
+	/** Whether the executable is already resolved. */
+	bool done;
+	/** Whether to free(path). */
+	bool free;
+};
+
+/** Free a $PATH resolution context. */
+static void bfs_resolve_free(struct bfs_resolver *res) {
+	if (res->free) {
+		free(res->path);
+	}
+	free(res->buf);
+}
+
+/** Get the next component in the $PATH. */
+static bool bfs_resolve_next(const char **path, const char **next, size_t *len) {
+	*path = *next;
+	if (!*path) {
+		return false;
+	}
+
+	*next = strchr(*path, ':');
+	if (*next) {
+		*len = *next - *path;
+		++*next;
 	} else {
-		return -1;
+		*len = strlen(*path);
 	}
+
+	if (*len == 0) {
+		// POSIX 8.3: "A zero-length prefix is a legacy feature that
+		// indicates the current working directory."
+		*path = ".";
+		*len = 1;
+	}
+
+	return true;
 }
 
-int bfs_spawn_addsetrlimit(struct bfs_spawn *ctx, int resource, const struct rlimit *rl) {
-	struct bfs_spawn_action *action = bfs_spawn_add(ctx, BFS_SPAWN_SETRLIMIT);
-	if (action) {
-		action->resource = resource;
-		action->rlimit = *rl;
+/** Finish resolving an executable, potentially from the child process. */
+static int bfs_resolve_late(struct bfs_resolver *res) {
+	if (res->done) {
 		return 0;
+	}
+
+	char *buf = res->buf;
+	char *end = buf + res->len;
+
+	const char *path;
+	const char *next = res->path;
+	size_t len;
+	while (bfs_resolve_next(&path, &next, &len)) {
+		char *cur = xstpencpy(buf, end, path, len);
+		cur = xstpecpy(cur, end, "/");
+		cur = xstpecpy(cur, end, res->exe);
+		if (cur == end) {
+			bfs_bug("PATH resolution buffer too small");
+			errno = ENOMEM;
+			return -1;
+		}
+
+		if (xfaccessat(AT_FDCWD, buf, X_OK) == 0) {
+			res->exe = buf;
+			res->done = true;
+			return 0;
+		}
+	}
+
+	errno = ENOENT;
+	return -1;
+}
+
+/** Check if we can skip path resolution entirely. */
+static bool bfs_can_skip_resolve(const struct bfs_resolver *res, const struct bfs_spawn *ctx) {
+	if (ctx && !(ctx->flags & BFS_SPAWN_USE_PATH)) {
+		return true;
+	}
+
+	if (strchr(res->exe, '/')) {
+		return true;
+	}
+
+	return false;
+}
+
+/** Check if any $PATH components are relative. */
+static bool bfs_resolve_relative(const struct bfs_resolver *res) {
+	const char *path;
+	const char *next = res->path;
+	size_t len;
+	while (bfs_resolve_next(&path, &next, &len)) {
+		if (path[0] != '/') {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/** Check if we can resolve the executable before file actions. */
+static bool bfs_can_resolve_early(const struct bfs_resolver *res, const struct bfs_spawn *ctx) {
+	if (!bfs_resolve_relative(res)) {
+		return true;
+	}
+
+	if (ctx) {
+		for_slist (const struct bfs_spawn_action, action, ctx) {
+			if (action->op == BFS_SPAWN_FCHDIR) {
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+/** Get the required path resolution buffer size. */
+static size_t bfs_resolve_capacity(const struct bfs_resolver *res) {
+	size_t max = 0;
+
+	const char *path;
+	const char *next = res->path;
+	size_t len;
+	while (bfs_resolve_next(&path, &next, &len)) {
+		if (len > max) {
+			max = len;
+		}
+	}
+
+	// path + "/" + exe + '\0'
+	return max + 1 + strlen(res->exe) + 1;
+}
+
+/** Begin resolving an executable, from the parent process. */
+static int bfs_resolve_early(struct bfs_resolver *res, const char *exe, const struct bfs_spawn *ctx) {
+	*res = (struct bfs_resolver) {
+		.exe = exe,
+	};
+
+	if (bfs_can_skip_resolve(res, ctx)) {
+		// Do this check eagerly, even though posix_spawn()/execv() also
+		// would, because:
+		//
+		//     - faccessat() is faster than fork()/clone() + execv()
+		//     - posix_spawn() is not guaranteed to report ENOENT
+		if (xfaccessat(AT_FDCWD, exe, X_OK) == 0) {
+			res->done = true;
+			return 0;
+		} else {
+			return -1;
+		}
+	}
+
+	res->path = getenv("PATH");
+	if (!res->path) {
+#if defined(_CS_PATH)
+		res->path = xconfstr(_CS_PATH);
+		res->free = true;
+#elif defined(_PATH_DEFPATH)
+		res->path = _PATH_DEFPATH;
+#else
+		errno = ENOENT;
+#endif
+	}
+	if (!res->path) {
+		goto fail;
+	}
+
+	bool can_finish = bfs_can_resolve_early(res, ctx);
+
+#if BFS_POSIX_SPAWNP_AFTER_FCHDIR
+	bool use_posix = ctx && (ctx->flags & BFS_SPAWN_USE_POSIX);
+	if (!can_finish && use_posix) {
+		// posix_spawnp() will do the resolution, so don't bother
+		// allocating a buffer
+		return 0;
+	}
+#endif
+
+	res->len = bfs_resolve_capacity(res);
+	res->buf = malloc(res->len);
+	if (!res->buf) {
+		goto fail;
+	}
+
+	if (can_finish && bfs_resolve_late(res) != 0) {
+		goto fail;
+	}
+
+	return 0;
+
+fail:
+	bfs_resolve_free(res);
+	return -1;
+}
+
+#if BFS_POSIX_SPAWN >= 0
+
+/** bfs_spawn() implementation using posix_spawn(). */
+static pid_t bfs_posix_spawn(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) {
+	pid_t ret;
+
+	if (res->done) {
+		errno = posix_spawn(&ret, res->exe, &ctx->actions, &ctx->attr, argv, envp);
 	} else {
+		errno = posix_spawnp(&ret, res->exe, &ctx->actions, &ctx->attr, argv, envp);
+	}
+
+	if (errno != 0) {
 		return -1;
 	}
+
+	return ret;
 }
 
+/** Check if we can use posix_spawn(). */
+static bool bfs_use_posix_spawn(const struct bfs_resolver *res, const struct bfs_spawn *ctx) {
+	if (!(ctx->flags & BFS_SPAWN_USE_POSIX)) {
+		return false;
+	}
+
+#if !BFS_POSIX_SPAWNP_AFTER_FCHDIR
+	if (!res->done) {
+		return false;
+	}
+#endif
+
+	return true;
+}
+
+#endif // BFS_POSIX_SPAWN >= 0
+
 /** Actually exec() the new process. */
-static void bfs_spawn_exec(const char *exe, const struct bfs_spawn *ctx, char **argv, char **envp, int pipefd[2]) {
+_noreturn
+static void bfs_spawn_exec(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp, const sigset_t *mask, int pipefd[2]) {
 	xclose(pipefd[0]);
 
-	for (const struct bfs_spawn_action *action = ctx ? ctx->head : NULL; action; action = action->next) {
+	for_slist (const struct bfs_spawn_action, action, ctx) {
+		int fd;
+
 		// Move the error-reporting pipe out of the way if necessary...
 		if (action->out_fd == pipefd[1]) {
-			int fd = dup_cloexec(pipefd[1]);
+			fd = dup_cloexec(pipefd[1]);
 			if (fd < 0) {
 				goto fail;
 			}
@@ -156,6 +559,17 @@ static void bfs_spawn_exec(const char *exe, const struct bfs_spawn *ctx, char **
 		}
 
 		switch (action->op) {
+		case BFS_SPAWN_OPEN:
+			fd = open(action->path, action->flags, action->mode);
+			if (fd < 0) {
+				goto fail;
+			}
+			if (fd != action->out_fd) {
+				if (dup2(fd, action->out_fd) < 0) {
+					goto fail;
+				}
+			}
+			break;
 		case BFS_SPAWN_CLOSE:
 			if (close(action->out_fd) != 0) {
 				goto fail;
@@ -179,137 +593,140 @@ static void bfs_spawn_exec(const char *exe, const struct bfs_spawn *ctx, char **
 		}
 	}
 
-	execve(exe, argv, envp);
+	if (bfs_resolve_late(res) != 0) {
+		goto fail;
+	}
 
-	int error;
-fail:
-	error = errno;
+	// Reset signal handlers to their original values before we unblock
+	// signals, so that handlers don't run in both the parent and the child
+	if (sigreset() != 0) {
+		goto fail;
+	}
+
+	// Restore the original signal mask for the child process
+	errno = pthread_sigmask(SIG_SETMASK, mask, NULL);
+	if (errno != 0) {
+		goto fail;
+	}
+
+	execve(res->exe, argv, envp);
+
+fail:;
+	int error = errno;
 
 	// In case of a write error, the parent will still see that we exited
 	// unsuccessfully, but won't know why
-	(void) xwrite(pipefd[1], &error, sizeof(error));
+	(void)xwrite(pipefd[1], &error, sizeof(error));
 
 	xclose(pipefd[1]);
 	_Exit(127);
 }
 
-pid_t bfs_spawn(const char *exe, const struct bfs_spawn *ctx, char **argv, char **envp) {
-	extern char **environ;
-	if (!envp) {
-		envp = environ;
-	}
-
-	enum bfs_spawn_flags flags = ctx ? ctx->flags : 0;
-	char *resolved = NULL;
-	if (flags & BFS_SPAWN_USEPATH) {
-		exe = resolved = bfs_spawn_resolve(exe);
-		if (!resolved) {
-			return -1;
-		}
-	}
-
+/** bfs_spawn() implementation using fork()/exec(). */
+static pid_t bfs_fork_spawn(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) {
 	// Use a pipe to report errors from the child
 	int pipefd[2];
 	if (pipe_cloexec(pipefd) != 0) {
-		free(resolved);
 		return -1;
 	}
 
+	// Block signals before fork() so handlers don't run in the child
+	sigset_t new_mask;
+	if (sigfillset(&new_mask) != 0) {
+		goto fail;
+	}
+	sigset_t old_mask;
+	errno = pthread_sigmask(SIG_BLOCK, &new_mask, &old_mask);
+	if (errno != 0) {
+		goto fail;
+	}
+
+#if BFS_HAS__FORK
+	pid_t pid = _Fork();
+#else
 	pid_t pid = fork();
-	if (pid < 0) {
-		close_quietly(pipefd[1]);
-		close_quietly(pipefd[0]);
-		free(resolved);
-		return -1;
-	} else if (pid == 0) {
+#endif
+	if (pid == 0) {
 		// Child
-		bfs_spawn_exec(exe, ctx, argv, envp, pipefd);
+		bfs_spawn_exec(res, ctx, argv, envp, &old_mask, pipefd);
+	}
+
+	// Restore the original signal mask
+	errno = pthread_sigmask(SIG_SETMASK, &old_mask, NULL);
+	bfs_everify(errno == 0, "pthread_sigmask()");
+
+	if (pid < 0) {
+		// fork() failed
+		goto fail;
 	}
 
-	// Parent
 	xclose(pipefd[1]);
-	free(resolved);
 
 	int error;
 	ssize_t nbytes = xread(pipefd[0], &error, sizeof(error));
 	xclose(pipefd[0]);
 	if (nbytes == sizeof(error)) {
-		int wstatus;
-		waitpid(pid, &wstatus, 0);
+		xwaitpid(pid, NULL, 0);
 		errno = error;
 		return -1;
 	}
 
 	return pid;
+
+fail:
+	close_quietly(pipefd[1]);
+	close_quietly(pipefd[0]);
+	return -1;
 }
 
-char *bfs_spawn_resolve(const char *exe) {
-	if (strchr(exe, '/')) {
-		return strdup(exe);
+/** Call the right bfs_spawn() implementation. */
+static pid_t bfs_spawn_impl(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) {
+#if BFS_POSIX_SPAWN >= 0
+	if (bfs_use_posix_spawn(res, ctx)) {
+		return bfs_posix_spawn(res, ctx, argv, envp);
 	}
-
-	const char *path = getenv("PATH");
-
-	char *confpath = NULL;
-	if (!path) {
-#if defined(_CS_PATH)
-		path = confpath = xconfstr(_CS_PATH);
-#elif defined(_PATH_DEFPATH)
-		path = _PATH_DEFPATH;
-#else
-		errno = ENOENT;
 #endif
-	}
-	if (!path) {
-		return NULL;
-	}
 
-	size_t cap = 0;
-	char *ret = NULL;
-	while (true) {
-		const char *end = strchr(path, ':');
-		size_t len = end ? (size_t)(end - path) : strlen(path);
-
-		// POSIX 8.3: "A zero-length prefix is a legacy feature that
-		// indicates the current working directory."
-		if (len == 0) {
-			path = ".";
-			len = 1;
-		}
+	return bfs_fork_spawn(res, ctx, argv, envp);
+}
 
-		size_t total = len + 1 + strlen(exe) + 1;
-		if (cap < total) {
-			char *grown = realloc(ret, total);
-			if (!grown) {
-				goto fail;
-			}
-			ret = grown;
-			cap = total;
-		}
+pid_t bfs_spawn(const char *exe, const struct bfs_spawn *ctx, char **argv, char **envp) {
+	// execvp()/posix_spawnp() are typically implemented with repeated
+	// execv() calls for each $PATH component until one succeeds.  It's
+	// faster to resolve the full path ahead of time.
+	struct bfs_resolver res;
+	if (bfs_resolve_early(&res, exe, ctx) != 0) {
+		return -1;
+	}
 
-		memcpy(ret, path, len);
-		if (ret[len - 1] != '/') {
-			ret[len++] = '/';
-		}
-		strcpy(ret + len, exe);
+	extern char **environ;
+	if (!envp) {
+		envp = environ;
+	}
 
-		if (xfaccessat(AT_FDCWD, ret, X_OK) == 0) {
-			break;
-		}
+	pid_t ret = bfs_spawn_impl(&res, ctx, argv, envp);
+	bfs_resolve_free(&res);
+	return ret;
+}
 
-		if (!end) {
-			errno = ENOENT;
-			goto fail;
-		}
+char *bfs_spawn_resolve(const char *exe) {
+	struct bfs_resolver res;
+	if (bfs_resolve_early(&res, exe, NULL) != 0) {
+		return NULL;
+	}
+	if (bfs_resolve_late(&res) != 0) {
+		bfs_resolve_free(&res);
+		return NULL;
+	}
 
-		path = end + 1;
+	char *ret;
+	if (res.exe == res.buf) {
+		ret = res.buf;
+		res.buf = NULL;
+	} else {
+		ret = strdup(res.exe);
 	}
 
-	free(confpath);
+	bfs_resolve_free(&res);
 	return ret;
-
-fail:
-	free(confpath);
-	free(ret);
-	return NULL;
 }