process-util: Move Xwayland fork helpers to shared

We'll want to reuse these inside desktop-shell as well as the Weston
frontend.

Signed-off-by: Daniel Stone <daniels@collabora.com>

3 files changed, 235 insertions, 0 deletions

diff --git a/shared/meson.build b/shared/meson.build
index d7936fe5..8b71fb87 100644
--- a/shared/meson.build
+++ b/shared/meson.build
@@ -4,6 +4,7 @@ srcs_libshared = [
 	'signal.c',
 	'file-util.c',
 	'os-compatibility.c',
+        'process-util.c',
 ]
 deps_libshared = [dep_wayland_client, dep_wayland_server]
 
diff --git a/shared/process-util.c b/shared/process-util.c
new file mode 100644
index 00000000..9b9ed00e
--- /dev/null
+++ b/shared/process-util.c
@@ -0,0 +1,151 @@
+/*
+ * Copyright 2022 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <wayland-util.h>
+
+#include "helpers.h"
+#include "os-compatibility.h"
+#include "process-util.h"
+#include "string-helpers.h"
+
+extern char **environ; /* defined by libc */
+
+void
+fdstr_update_str1(struct fdstr *s)
+{
+	snprintf(s->str1, sizeof(s->str1), "%d", s->fds[1]);
+}
+
+void
+fdstr_set_fd1(struct fdstr *s, int fd)
+{
+	s->fds[0] = -1;
+	s->fds[1] = fd;
+	fdstr_update_str1(s);
+}
+
+bool
+fdstr_clear_cloexec_fd1(struct fdstr *s)
+{
+	return os_fd_clear_cloexec(s->fds[1]) >= 0;
+}
+
+void
+fdstr_close_all(struct fdstr *s)
+{
+	unsigned i;
+
+	for (i = 0; i < ARRAY_LENGTH(s->fds); i++) {
+		close(s->fds[i]);
+		s->fds[i] = -1;
+	}
+}
+
+void
+custom_env_init_from_environ(struct custom_env *env)
+{
+	char **it;
+	char **ep;
+
+	wl_array_init(&env->p);
+	env->finalized = false;
+
+	for (it = environ; *it; it++) {
+		ep = wl_array_add(&env->p, sizeof *ep);
+		assert(ep);
+		*ep = strdup(*it);
+		assert(*ep);
+	}
+}
+
+void
+custom_env_fini(struct custom_env *env)
+{
+	char **ep;
+
+	wl_array_for_each(ep, &env->p)
+		free(*ep);
+
+	wl_array_release(&env->p);
+}
+
+static char **
+custom_env_find_element(struct custom_env *env, const char *name)
+{
+	char **ep;
+	size_t name_len = strlen(name);
+
+	wl_array_for_each(ep, &env->p) {
+		char *entry = *ep;
+
+		if (strncmp(entry, name, name_len) == 0 &&
+		    entry[name_len] == '=') {
+			return ep;
+		}
+	}
+
+	return NULL;
+}
+
+void
+custom_env_set(struct custom_env *env, const char *name, const char *value)
+{
+	char **ep;
+
+	assert(strchr(name, '=') == NULL);
+	assert(!env->finalized);
+
+	ep = custom_env_find_element(env, name);
+	if (ep)
+		free(*ep);
+	else
+		ep = wl_array_add(&env->p, sizeof *ep);
+	assert(ep);
+
+	str_printf(ep, "%s=%s", name, value);
+	assert(*ep);
+}
+
+char *const *
+custom_env_get_envp(struct custom_env *env)
+{
+	char **ep;
+
+	/* add terminating NULL */
+	ep = wl_array_add(&env->p, sizeof *ep);
+	assert(ep);
+	*ep = NULL;
+
+	env->finalized = true;
+
+	return env->p.data;
+}
diff --git a/shared/process-util.h b/shared/process-util.h
new file mode 100644
index 00000000..56c1b46d
--- /dev/null
+++ b/shared/process-util.h
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2022 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <wayland-util.h>
+
+#include "os-compatibility.h"
+#include "string-helpers.h"
+
+/**
+ * A container for file descriptors and their string representations, designed
+ * to be used when forking child processes.
+ *
+ * fds[0] is generally used as the file descriptor held within the parent
+ * process to communicate with the child, and fds[1] as the child's counterpart.
+ *
+ * str1[] is used as a string representation of fds[1].
+ */
+struct fdstr {
+	char str1[12];
+	int fds[2];
+};
+
+void
+fdstr_update_str1(struct fdstr *s);
+
+void
+fdstr_set_fd1(struct fdstr *s, int fd);
+
+bool
+fdstr_clear_cloexec_fd1(struct fdstr *s);
+
+void
+fdstr_close_all(struct fdstr *s);
+
+
+/**
+ * A container for environment variables, designed to be used when forking child
+ * processes, as setenv() and anything which allocates memory cannot be used
+ * between fork() and exec().
+ */
+struct custom_env {
+	struct wl_array p;
+	bool finalized;
+};
+
+void
+custom_env_init_from_environ(struct custom_env *env);
+
+void
+custom_env_fini(struct custom_env *env);
+
+void
+custom_env_set(struct custom_env *env, const char *name, const char *value);
+
+char *const *
+custom_env_get_envp(struct custom_env *env);