zipl: Add BootLoaderSpec support

The BootLoaderSpec (BLS) defines a file format for boot configurations,
so bootloaders can parse these files and create their boot menu entries
by using the information provided by them [0].

This allow to configure the boot items as drop-in files in a directory
instead of having to parse and modify a bootloader configuration file.

If the /boot/loader/entries exists and there are BLS files there, then
these are parsed and configuration sections are added without the need
to have these in a zipl.conf file.

A different BLS directory can be specified from the command line using
the --blsdir option.

[0]: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/

GitHub-ID: #28
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zipl/include/scan.h

@@ -119,6 +119,7 @@ extern enum scan_key_state scan_key_table[SCAN_SECTION_NUM][SCAN_KEYWORD_NUM];
 
 
 int scan_file(const char* filename, struct scan_token** array);
+int scan_bls(const char* blsdir, struct scan_token** token, int scan_size);
 void scan_free(struct scan_token* array);
 char* scan_keyword_name(enum scan_keyword_id id);
 int scan_check_defaultboot(struct scan_token* scan);

zipl/include/zipl.h

@@ -43,6 +43,7 @@
 
 #define ZIPL_CONF_VAR			"ZIPLCONF"
 #define ZIPL_DEFAULT_CONF		"/etc/zipl.conf"
+#define ZIPL_DEFAULT_BLSDIR		"/boot/loader/entries"
 
 #define MENU_DEFAULT_PROMPT		0
 #define MENU_DEFAULT_TIMEOUT		0

zipl/man/zipl.8

@@ -25,7 +25,7 @@ loading a data file to initialize named saved segments (NSS)
 Each of these operations is characterized by a boot configuration, i.e. a
 set of required parameters.
 .B zipl
-supports two ways of specifying a boot configuration:
+supports three ways of specifying a boot configuration:
 .IP "     -"
 .B command line:
 all parameters are provided through the command line switches described below.
@@ -37,6 +37,11 @@ parameters are provided by sections defined in a configuration file (see
 Using a configuration file, you can either specify a single boot configuration
 or a menu, i.e. a list of configurations from which users can choose at boot
 time.
+.IP "     -"
+.B BLS config files:
+boot configurations are specified using BootLoaderSpec (BLS) configuration files. The
+.BR zipl.conf (5)
+configuration file is still used to specify parameters or aditional boot configurations.
 .PP
 
 To use a single boot configuration section, provide its name as parameter to
@@ -117,6 +122,11 @@ Print version information, then exit.
 Use the specified <CONFIG FILE>. If none is supplied, the environment
 variable ZIPLCONF is evaluated if set, otherwise /etc/zipl.conf is used.
 
+.TP
+.BR "\-b <BLS DIRECTORY>" " or " "\-\-blsdir=<BLS DIRECTORY>"
+Use the specified <BLS DIRECTORY> to parse BootLoaderSpec config files.
+If none is supplied, the /boot/loader/entries directory is used.
+
 .TP
 .BR "\-t <TARGET DIRECTORY>" " or " "\-\-target=<TARGET DIRECTORY>"
 Use the specified <TARGET DIRECTORY>. 

zipl/man/zipl.conf.5

@@ -117,6 +117,27 @@ timeout     = 0
 .br
 .PP
 
+.B BootLoaderSpec configuration files
+
+Another way to specify IPL sections is to use BLS config files. These are
+configuration files located by default at /boot/loader/entries, but another
+location can be specified using the '\-\-blsdir' option of zipl.
+
+.IP
+# An example for a BLS configuration file
+.br
+
+version 4.15.9
+.br
+linux /vmlinuz-4.15.9
+.br
+initrd /initramfs-4.15.9
+.br
+options root=/dev/dasda1 console=ttyS0
+.PP
+
+The location of the linux and initrd has to be specified relative to the boot partition. The BLS config files are only used to specify the IPL sections, a zipl.conf configuration files is still needed for global parameters.
+
 .B Boot menu
 
 The

zipl/src/job.c

@@ -27,6 +27,7 @@
 /* Command line options */
 static struct option options[] = {
 	{ "config",		required_argument,	NULL, 'c'},
+	{ "blsdir",		required_argument,	NULL, 'b'},
 	{ "target",		required_argument,	NULL, 't'},
 	{ "targetbase",         required_argument,      NULL, 0xaa},
 	{ "targettype",         required_argument,      NULL, 0xab},
@@ -55,11 +56,12 @@ static struct option options[] = {
 };
 
 /* Command line option abbreviations */
-static const char option_string[] = "-c:t:i:r:p:P:d:D:M:s:m:hHnVvaT:fk:";
+static const char option_string[] = "-c:b:t:i:r:p:P:d:D:M:s:m:hHnVvaT:fk:";
 
 struct command_line {
 	char* data[SCAN_KEYWORD_NUM];
 	char* config;
+	char *blsdir;
 	char* menu;
 	char* section;
 	int help;
@@ -197,6 +199,14 @@ get_command_line(int argc, char* argv[], struct command_line* line)
 			} else
 				cmdline.config = optarg;
 			break;
+		case 'b':
+			if (cmdline.blsdir != NULL) {
+				error_reason("Option 'blsdir' specified more "
+					     "than once");
+				rc = -1;
+			} else
+				cmdline.blsdir = optarg;
+			break;
 		case 'm':
 			if (cmdline.menu != NULL) {
 				error_reason("Option 'menu' specified more "
@@ -1731,6 +1741,7 @@ get_job_from_config_file(struct command_line* cmdline, struct job_data* job)
 	struct scan_token* scan;
 	struct scan_token* new_scan;
 	char* filename;
+	char *blsdir;
 	char* source;
 	int rc, scan_size;
 
@@ -1755,6 +1766,17 @@ get_job_from_config_file(struct command_line* cmdline, struct job_data* job)
 		error_text("Config file '%s'", filename);
 		return scan_size;
 	}
+	/* Check if a BLS directory was provided on command line */
+	if (cmdline->blsdir != NULL) {
+		blsdir = cmdline->blsdir;
+	} else {
+		blsdir = ZIPL_DEFAULT_BLSDIR;
+	}
+	rc = scan_bls(blsdir, &scan, scan_size);
+	if (rc) {
+		error_text("BLS parsing '%s'", blsdir);
+		return rc;
+	}
 	if ((cmdline->menu == NULL) && (cmdline->section == NULL)) {
 		rc = scan_check_defaultboot(scan);
 		if (rc < 0) {

zipl/src/scan.c

@@ -16,13 +16,21 @@
 #define __USE_ISOC99
 #endif
 
+/* Need GNU function strverscmp() in dirent.h */
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include <ctype.h>
+#include <dirent.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include <sys/stat.h>
+
 #include "lib/util_base.h"
 
 #include "boot.h"
@@ -633,6 +641,177 @@ scan_file(const char* filename, struct scan_token** token)
 }
 
 
+static int
+bls_filter(const struct dirent *ent)
+{
+	int offset = strlen(ent->d_name) - strlen(".conf");
+
+	if (offset < 0)
+		return 0;
+
+	return strncmp(ent->d_name + offset, ".conf", strlen(".conf")) == 0;
+}
+
+
+static int
+bls_sort(const struct dirent **ent_a, const struct dirent **ent_b)
+{
+	return strverscmp((*ent_a)->d_name, (*ent_b)->d_name);
+}
+
+
+static int
+scan_append_section_heading(struct scan_token* scan, int* index, char* name);
+static int
+scan_append_keyword_assignment(struct scan_token* scan, int* index,
+			       enum scan_keyword_id id, char* value);
+
+
+static int
+scan_bls_field(struct misc_file_buffer *file, struct scan_token* scan,
+	       int* index)
+{
+	int current;
+	int key_start, key_end;
+	int val_start, val_end;
+	char *val;
+
+	for (key_start = file->pos; ; file->pos++) {
+		current = misc_get_char(file, 0);
+
+		if (isblank(current)) {
+			key_end = file->pos;
+			skip_blanks(file);
+			val_start = file->pos;
+			break;
+		}
+
+		if (!isalnum(current) && current != '_' && current != '-')
+			return -1;
+	}
+
+	for (; ; file->pos++) {
+		current = misc_get_char(file, 0);
+
+		if (current == '\n' || current == EOF)
+			break;
+	}
+
+	val_end = file->pos;
+	file->buffer[key_end] = '\0';
+	file->buffer[val_end] = '\0';
+
+	if (strncmp("version", &file->buffer[key_start], key_end - key_start) == 0) {
+		scan_append_section_heading(scan, index, &file->buffer[val_start]);
+	}
+
+	if (strncmp("linux", &file->buffer[key_start], key_end - key_start) == 0) {
+		misc_asprintf(&val, "%s", &file->buffer[val_start]);
+		scan_append_keyword_assignment(scan, index, scan_keyword_image, val);
+		free(val);
+	}
+
+	if (strncmp("options", &file->buffer[key_start], key_end - key_start) == 0) {
+		scan_append_keyword_assignment(scan, index, scan_keyword_parameters,
+					       &file->buffer[val_start]);
+	}
+
+	if (strncmp("initrd", &file->buffer[key_start], key_end - key_start) == 0) {
+		misc_asprintf(&val, "%s", &file->buffer[val_start]);
+		scan_append_keyword_assignment(scan, index, scan_keyword_ramdisk, val);
+		free(val);
+	}
+
+	return 0;
+}
+
+
+int
+scan_bls(const char* blsdir, struct scan_token** token, int scan_size)
+{
+	int count = 0;
+	int size, remaining = 0, n, current, rc = -1;
+	struct scan_token* buffer;
+	struct scan_token* array = *token;
+	struct dirent** bls_entries;
+	struct misc_file_buffer file;
+	struct stat sb;
+	char filename[PATH_MAX];
+
+	if (!(stat(blsdir, &sb) == 0 && S_ISDIR(sb.st_mode)))
+		return 0;
+
+	n = scandir(blsdir, &bls_entries, bls_filter, bls_sort);
+	if (n <= 0)
+		return n;
+
+	while (array[count].id != 0)
+		count++;
+
+	remaining = scan_size - count;
+
+	if (remaining < n) {
+		size = scan_size - remaining + n;
+		buffer = (struct scan_token *)misc_malloc(size * sizeof(struct scan_token));
+		if (!buffer)
+			goto err;
+		memset(buffer, 0, size * sizeof(struct scan_token));
+		memcpy(buffer, array, count * sizeof(struct scan_token));
+	} else {
+		buffer = array;
+	}
+
+	while (n--) {
+		sprintf(filename, "%s/%s", blsdir, bls_entries[n]->d_name);
+		printf("Using BLS config file '%s'\n", filename);
+
+		rc = misc_get_file_buffer(filename, &file);
+		if (rc)
+			goto err;
+
+		while ((size_t)file.pos < file.length) {
+			current = misc_get_char(&file, 0);
+			switch (current) {
+			case '#':
+				file.pos++;
+				skip_line(&file);
+				break;
+			case EOF:
+				break;
+			case '\t':
+			case '\0':
+			case ' ':
+				file.pos++;
+				break;
+			default:
+				rc = scan_bls_field(&file, buffer, &count);
+				if (rc) {
+					error_reason("Incorrect BLS field in "
+						"config file %s\n", filename);
+					goto err;
+				}
+				break;
+			}
+		}
+
+		misc_free_file_buffer(&file);
+		free(bls_entries[n]);
+	}
+
+	*token = buffer;
+	rc = 0;
+err:
+	if (n > 0) {
+		do {
+			free(bls_entries[n]);
+		} while (n-- > 0);
+	}
+
+	free(bls_entries);
+	return rc;
+}
+
+
 /* Search scanned tokens SCAN for a section/menu heading (according to
  * TYPE) of the given NAME, beginning at token OFFSET. Return the index of
  * the section/menu heading on success, a negative value on error. */

zipl/src/zipl.c

@@ -54,6 +54,7 @@ static const char* usage_text[] = {
 "-h, --help                      Print this help, then exit",
 "-v, --version                   Print version information, then exit",
 "-c, --config CONFIGFILE         Read configuration from CONFIGFILE",
+"-b, --blsdir BLSDIR             Parse BootLoaderSpec files from BLSDIR",
 "-t, --target TARGETDIR          Write bootmap file to TARGETDIR and install",
 "                                bootloader on device containing TARGETDIR",
 "    --targetbase BASEDEVICE     Install bootloader on BASEDEVICE",