lxc_init: add custom argument parser

lxc_init.c should not depend on tools/arguments.{c,h}, thus it needs its own custom argument parser

Signed-off-by: RicardoSanchezA <ricardo.sanchez@utexas.edu>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/Makefile.am

@@ -275,7 +275,7 @@ lxc_device_SOURCES = tools/lxc_device.c tools/arguments.c
 lxc_execute_SOURCES = tools/lxc_execute.c tools/arguments.c
 lxc_freeze_SOURCES = tools/lxc_freeze.c tools/arguments.c
 lxc_info_SOURCES = tools/lxc_info.c tools/arguments.c
-init_lxc_SOURCES = lxc_init.c tools/arguments.c
+init_lxc_SOURCES = lxc_init.c
 lxc_monitor_SOURCES = tools/lxc_monitor.c tools/arguments.c
 lxc_ls_SOURCES = tools/lxc_ls.c tools/arguments.c
 lxc_copy_SOURCES = tools/lxc_copy.c tools/arguments.c
@@ -303,8 +303,7 @@ endif
 if HAVE_STATIC_LIBCAP
 sbin_PROGRAMS += init.lxc.static
 
-init_lxc_static_SOURCES = lxc_init.c error.c log.c initutils.c caps.c \
-			  tools/arguments.c
+init_lxc_static_SOURCES = lxc_init.c error.c log.c initutils.c caps.c
 
 if !HAVE_GETLINE
 if HAVE_FGETLN

src/lxc/initutils.c

@@ -21,6 +21,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include <sys/prctl.h>
+
 #include "initutils.h"
 #include "log.h"
 
@@ -296,3 +298,107 @@ FILE *fopen_cloexec(const char *path, const char *mode)
 	errno = saved_errno;
 	return ret;
 }
+
+/*
+ * Sets the process title to the specified title. Note that this may fail if
+ * the kernel doesn't support PR_SET_MM_MAP (kernels <3.18).
+ */
+int setproctitle(char *title)
+{
+	static char *proctitle = NULL;
+	char buf[2048], *tmp;
+	FILE *f;
+	int i, len, ret = 0;
+
+	/* We don't really need to know all of this stuff, but unfortunately
+	 * PR_SET_MM_MAP requires us to set it all at once, so we have to
+	 * figure it out anyway.
+	 */
+	unsigned long start_data, end_data, start_brk, start_code, end_code,
+			start_stack, arg_start, arg_end, env_start, env_end,
+			brk_val;
+	struct prctl_mm_map prctl_map;
+
+	f = fopen_cloexec("/proc/self/stat", "r");
+	if (!f) {
+		return -1;
+	}
+
+	tmp = fgets(buf, sizeof(buf), f);
+	fclose(f);
+	if (!tmp) {
+		return -1;
+	}
+
+	/* Skip the first 25 fields, column 26-28 are start_code, end_code,
+	 * and start_stack */
+	tmp = strchr(buf, ' ');
+	for (i = 0; i < 24; i++) {
+		if (!tmp)
+			return -1;
+		tmp = strchr(tmp+1, ' ');
+	}
+	if (!tmp)
+		return -1;
+
+	i = sscanf(tmp, "%lu %lu %lu", &start_code, &end_code, &start_stack);
+	if (i != 3)
+		return -1;
+
+	/* Skip the next 19 fields, column 45-51 are start_data to arg_end */
+	for (i = 0; i < 19; i++) {
+		if (!tmp)
+			return -1;
+		tmp = strchr(tmp+1, ' ');
+	}
+
+	if (!tmp)
+		return -1;
+
+	i = sscanf(tmp, "%lu %lu %lu %*u %*u %lu %lu",
+		&start_data,
+		&end_data,
+		&start_brk,
+		&env_start,
+		&env_end);
+	if (i != 5)
+		return -1;
+
+	/* Include the null byte here, because in the calculations below we
+	 * want to have room for it. */
+	len = strlen(title) + 1;
+
+	proctitle = realloc(proctitle, len);
+	if (!proctitle)
+		return -1;
+
+	arg_start = (unsigned long) proctitle;
+	arg_end = arg_start + len;
+
+	brk_val = syscall(__NR_brk, 0);
+
+	prctl_map = (struct prctl_mm_map) {
+		.start_code = start_code,
+		.end_code = end_code,
+		.start_stack = start_stack,
+		.start_data = start_data,
+		.end_data = end_data,
+		.start_brk = start_brk,
+		.brk = brk_val,
+		.arg_start = arg_start,
+		.arg_end = arg_end,
+		.env_start = env_start,
+		.env_end = env_end,
+		.auxv = NULL,
+		.auxv_size = 0,
+		.exe_fd = -1,
+	};
+
+	ret = prctl(PR_SET_MM, PR_SET_MM_MAP, (long) &prctl_map, sizeof(prctl_map), 0);
+	if (ret == 0)
+		strcpy((char*)arg_start, title);
+	else
+		INFO("setting cmdline failed - %s", strerror(errno));
+
+	return ret;
+}

src/lxc/initutils.h

@@ -25,17 +25,16 @@
 #define __LXC_INITUTILS_H
 
 #include <errno.h>
-#include <stdio.h>
+#include <fcntl.h>
+#include <inttypes.h>
 #include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/mount.h>
-#include <unistd.h>
-#include <string.h>
-#include <stdlib.h>
-#include <fcntl.h>
-
 
 #include "config.h"
 
@@ -44,11 +43,37 @@
 #define DEFAULT_ZFSROOT "lxc"
 #define DEFAULT_RBDPOOL "lxc"
 
+#ifndef PR_SET_MM
+#define PR_SET_MM 35
+#endif
+
+#ifndef PR_SET_MM_MAP
+#define PR_SET_MM_MAP 14
+
+struct prctl_mm_map {
+	uint64_t start_code;
+	uint64_t end_code;
+	uint64_t start_data;
+	uint64_t end_data;
+	uint64_t start_brk;
+	uint64_t brk;
+	uint64_t start_stack;
+	uint64_t arg_start;
+	uint64_t arg_end;
+	uint64_t env_start;
+	uint64_t env_end;
+	uint64_t *auxv;
+	uint32_t auxv_size;
+	uint32_t exe_fd;
+};
+#endif
+
 extern void lxc_setup_fs(void);
 extern const char *lxc_global_config_value(const char *option_name);
 
 /* open a file with O_CLOEXEC */
 extern void remove_trailing_slashes(char *p);
-FILE *fopen_cloexec(const char *path, const char *mode);
+extern FILE *fopen_cloexec(const char *path, const char *mode);
+extern int setproctitle(char *title);
 
 #endif /* __LXC_INITUTILS_H */