cgroups: flatten hierarchy

[mirror_lxc.git] / src / lxc / initutils.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
#include <sys/prctl.h>

#include "compiler.h"
#include "config.h"
#include "file_utils.h"
#include "initutils.h"
#include "log.h"
#include "macro.h"
#include "memory_utils.h"

#ifndef HAVE_STRLCPY
#include "include/strlcpy.h"
#endif

lxc_log_define(initutils, lxc);

static char *copy_global_config_value(char *p)
{
	int len = strlen(p);
	char *retbuf;

	if (len < 1)
		return NULL;

	if (p[len-1] == '\n') {
		p[len-1] = '\0';
		len--;
	}

	retbuf = malloc(len + 1);
	if (!retbuf)
		return NULL;

	(void)strlcpy(retbuf, p, len + 1);
	return retbuf;
}

const char *lxc_global_config_value(const char *option_name)
{
	static const char * const options[][2] = {
		{ "lxc.bdev.lvm.vg",        DEFAULT_VG      },
		{ "lxc.bdev.lvm.thin_pool", DEFAULT_THIN_POOL },
		{ "lxc.bdev.zfs.root",      DEFAULT_ZFSROOT },
		{ "lxc.bdev.rbd.rbdpool",   DEFAULT_RBDPOOL },
		{ "lxc.lxcpath",            NULL            },
		{ "lxc.default_config",     NULL            },
		{ "lxc.cgroup.pattern",     NULL            },
		{ "lxc.cgroup.use",         NULL            },
		{ NULL, NULL },
	};

	/* placed in the thread local storage pool for non-bionic targets */
#ifdef HAVE_TLS
	static thread_local const char *values[sizeof(options) / sizeof(options[0])] = {0};
#else
	static const char *values[sizeof(options) / sizeof(options[0])] = {0};
#endif

	/* user_config_path is freed as soon as it is used */
	char *user_config_path = NULL;

	/*
	 * The following variables are freed at bottom unconditionally.
	 * So NULL the value if it is to be returned to the caller
	 */
	char *user_default_config_path = NULL;
	char *user_lxc_path = NULL;
	char *user_cgroup_pattern = NULL;

	if (geteuid() > 0) {
		const char *user_home = getenv("HOME");
		if (!user_home)
			user_home = "/";

		user_config_path = malloc(sizeof(char) * (22 + strlen(user_home)));
		user_default_config_path = malloc(sizeof(char) * (26 + strlen(user_home)));
		user_lxc_path = malloc(sizeof(char) * (19 + strlen(user_home)));

		sprintf(user_config_path, "%s/.config/lxc/lxc.conf", user_home);
		sprintf(user_default_config_path, "%s/.config/lxc/default.conf", user_home);
		sprintf(user_lxc_path, "%s/.local/share/lxc/", user_home);
		user_cgroup_pattern = strdup("%n");
	}
	else {
		user_config_path = strdup(LXC_GLOBAL_CONF);
		user_default_config_path = strdup(LXC_DEFAULT_CONFIG);
		user_lxc_path = strdup(LXCPATH);
		user_cgroup_pattern = strdup(DEFAULT_CGROUP_PATTERN);
	}

	const char * const (*ptr)[2];
	size_t i;
	FILE *fin = NULL;

	for (i = 0, ptr = options; (*ptr)[0]; ptr++, i++) {
		if (!strcmp(option_name, (*ptr)[0]))
			break;
	}
	if (!(*ptr)[0]) {
		free(user_config_path);
		free(user_default_config_path);
		free(user_lxc_path);
		free(user_cgroup_pattern);
		errno = EINVAL;
		return NULL;
	}

	if (values[i]) {
		free(user_config_path);
		free(user_default_config_path);
		free(user_lxc_path);
		free(user_cgroup_pattern);
		return values[i];
	}

	fin = fopen_cloexec(user_config_path, "r");
	free(user_config_path);
	if (fin) {
		__do_free char *line = NULL;
		size_t len = 0;
		char *slider1, *slider2;

		while (getline(&line, &len, fin) > 0) {
			if (*line == '#')
				continue;

			slider1 = strstr(line, option_name);
			if (!slider1)
				continue;

			/* see if there was just white space in front
			 * of the option name
			 */
			for (slider2 = line; slider2 < slider1; slider2++)
				if (*slider2 != ' ' && *slider2 != '\t')
					break;

			if (slider2 < slider1)
				continue;

			slider1 = strchr(slider1, '=');
			if (!slider1)
				continue;

			/* see if there was just white space after
			 * the option name
			 */
			for (slider2 += strlen(option_name); slider2 < slider1;
			     slider2++)
				if (*slider2 != ' ' && *slider2 != '\t')
					break;

			if (slider2 < slider1)
				continue;

			slider1++;
			while (*slider1 && (*slider1 == ' ' || *slider1 == '\t'))
				slider1++;

			if (!*slider1)
				continue;

			if (strcmp(option_name, "lxc.lxcpath") == 0) {
				free(user_lxc_path);
				user_lxc_path = copy_global_config_value(slider1);
				remove_trailing_slashes(user_lxc_path);
				values[i] = user_lxc_path;
				user_lxc_path = NULL;
				goto out;
			}

			values[i] = copy_global_config_value(slider1);
			goto out;
		}
	}

	/* could not find value, use default */
	if (strcmp(option_name, "lxc.lxcpath") == 0) {
		remove_trailing_slashes(user_lxc_path);
		values[i] = user_lxc_path;
		user_lxc_path = NULL;
	}
	else if (strcmp(option_name, "lxc.default_config") == 0) {
		values[i] = user_default_config_path;
		user_default_config_path = NULL;
	}
	else if (strcmp(option_name, "lxc.cgroup.pattern") == 0) {
		values[i] = user_cgroup_pattern;
		user_cgroup_pattern = NULL;
	}
	else
		values[i] = (*ptr)[1];

	/* special case: if default value is NULL,
	 * and there is no config, don't view that
	 * as an error... */
	if (!values[i])
		errno = 0;

out:
	if (fin)
		fclose(fin);

	free(user_cgroup_pattern);
	free(user_default_config_path);
	free(user_lxc_path);

	return values[i];
}

/*
 * 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)
{
	__do_fclose FILE *f = NULL;
	int i, fd, len;
	char *buf_ptr, *tmp_proctitle;
	char buf[LXC_LINELEN];
	int ret = 0;
	ssize_t bytes_read = 0;
	static char *proctitle = NULL;

	/*
	 * 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;

	fd = fileno(f);
	if (fd < 0)
		return -1;

	bytes_read = lxc_read_nointr(fd, buf, sizeof(buf) - 1);
	if (bytes_read <= 0)
		return -1;

	buf[bytes_read] = '\0';

	/* Skip the first 25 fields, column 26-28 are start_code, end_code,
	 * and start_stack */
	buf_ptr = strchr(buf, ' ');
	for (i = 0; i < 24; i++) {
		if (!buf_ptr)
			return -1;
		buf_ptr = strchr(buf_ptr + 1, ' ');
	}
	if (!buf_ptr)
		return -1;

	i = sscanf(buf_ptr, "%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 (!buf_ptr)
			return -1;
		buf_ptr = strchr(buf_ptr + 1, ' ');
	}

	if (!buf_ptr)
		return -1;

	i = sscanf(buf_ptr, "%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;

	tmp_proctitle = realloc(proctitle, len);
	if (!tmp_proctitle)
		return -1;

	proctitle = tmp_proctitle;

	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, prctl_arg(PR_SET_MM_MAP), prctl_arg(&prctl_map),
		    prctl_arg(sizeof(prctl_map)), prctl_arg(0));
	if (ret == 0)
		(void)strlcpy((char *)arg_start, title, len);
	else
		SYSWARN("Failed to set cmdline");

	return ret;
}