discover/grub: Add blscfg command support to parse BootLoaderSpec files

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.

The GRUB 2 bootloader provides a blscfg command that parses these files
and creates menu entries using this information. Add support for it.

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

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>

1 files changed, 241 insertions, 0 deletions

diff --git a/discover/grub2/blscfg.c b/discover/grub2/blscfg.c
new file mode 100644
index 0000000..0f69f7e
--- /dev/null
+++ b/discover/grub2/blscfg.c
@@ -0,0 +1,241 @@
+
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dirent.h>
+
+#include <log/log.h>
+#include <file/file.h>
+#include <talloc/talloc.h>
+#include <i18n/i18n.h>
+
+#include "grub2.h"
+#include "discover/parser-conf.h"
+#include "discover/parser.h"
+
+#define BLS_DIR "/loader/entries"
+
+struct bls_state {
+	struct discover_boot_option *opt;
+	struct grub2_script *script;
+	const char *filename;
+	const char *title;
+	const char *version;
+	const char *machine_id;
+	const char *image;
+	const char *initrd;
+	const char *dtb;
+};
+
+static void bls_process_pair(struct conf_context *conf, const char *name,
+			     char *value)
+{
+	struct bls_state *state = conf->parser_info;
+	struct discover_boot_option *opt = state->opt;
+	struct boot_option *option = opt->option;
+	const char *boot_args;
+
+	if (streq(name, "title")) {
+		state->title = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "version")) {
+		state->version = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "machine-id")) {
+		state->machine_id = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "linux")) {
+		state->image = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "initrd")) {
+		state->initrd = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "devicetree")) {
+		state->dtb = talloc_strdup(state, value);
+		return;
+	}
+
+	if (streq(name, "options")) {
+		if (value[0] == '$') {
+			boot_args = script_env_get(state->script, value + 1);
+			if (!boot_args)
+				return;
+
+			option->boot_args = talloc_strdup(opt, boot_args);
+		} else {
+			option->boot_args = talloc_strdup(opt, value);
+		}
+		return;
+	}
+}
+
+static bool option_is_default(struct grub2_script *script,
+			      struct boot_option *option)
+{
+	const char *var;
+
+	var = script_env_get(script, "default");
+	if (!var)
+		return false;
+
+	if (!strcmp(var, option->id))
+		return true;
+
+	return !strcmp(var, option->name);
+}
+
+static void bls_finish(struct conf_context *conf)
+{
+	struct bls_state *state = conf->parser_info;
+	struct discover_context *dc = conf->dc;
+	struct discover_boot_option *opt = state->opt;
+	struct boot_option *option = opt->option;
+	const char *root;
+	char *filename;
+
+	if (!state->image) {
+		device_handler_status_dev_info(dc->handler, dc->device,
+					       _("linux field not found in %s"),
+					       state->filename);
+		return;
+	}
+
+	filename = basename(state->filename);
+	filename[strlen(filename) - strlen(".conf")] = '\0';
+
+	option->id = talloc_strdup(option, filename);
+
+	if (state->title)
+		option->name = talloc_strdup(option, state->title);
+	else if (state->machine_id && state->version)
+		option->name = talloc_asprintf(option, "%s %s",
+					       state->machine_id,
+					       state->version);
+	else if (state->version)
+		option->name = talloc_strdup(option, state->version);
+	else
+		option->name = talloc_strdup(option, state->image);
+
+	root = script_env_get(state->script, "root");
+
+	opt->boot_image = create_grub2_resource(opt, conf->dc->device,
+						root, state->image);
+
+	if (state->initrd)
+		opt->initrd = create_grub2_resource(opt, conf->dc->device,
+						    root, state->initrd);
+
+	if (state->dtb)
+		opt->dtb = create_grub2_resource(opt, conf->dc->device,
+						 root, state->dtb);
+
+	option->is_default = option_is_default(state->script, option);
+
+	discover_context_add_boot_option(dc, opt);
+
+	device_handler_status_dev_info(dc->handler, dc->device,
+				       _("Created menu entry from BLS file %s"),
+				       state->filename);
+}
+
+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_b)->d_name, (*ent_a)->d_name);
+}
+
+int builtin_blscfg(struct grub2_script *script,
+		void *data __attribute__((unused)),
+		int argc __attribute__((unused)),
+		char *argv[] __attribute__((unused)));
+
+int builtin_blscfg(struct grub2_script *script,
+		void *data __attribute__((unused)),
+		int argc __attribute__((unused)),
+		char *argv[] __attribute__((unused)))
+{
+	struct discover_context *dc = script->ctx;
+	struct dirent **bls_entries;
+	struct conf_context *conf;
+	struct bls_state *state;
+	char *buf, *filename;
+	int n, len, rc = -1;
+
+	conf = talloc_zero(dc, struct conf_context);
+	if (!conf)
+		return rc;
+
+	conf->dc = dc;
+	conf->get_pair = conf_get_pair_space;
+	conf->process_pair = bls_process_pair;
+	conf->finish = bls_finish;
+
+	n = parser_scandir(dc, BLS_DIR, &bls_entries, bls_filter, bls_sort);
+	if (n <= 0)
+		goto err;
+
+	while (n--) {
+		filename = talloc_asprintf(dc, BLS_DIR"/%s",
+					   bls_entries[n]->d_name);
+		if (!filename)
+			break;
+
+		state = talloc_zero(conf, struct bls_state);
+		if (!state)
+			break;
+
+		state->opt = discover_boot_option_create(dc, dc->device);
+		if (!state->opt)
+			break;
+
+		state->script = script;
+		state->filename = filename;
+		conf->parser_info = state;
+
+		rc = parser_request_file(dc, dc->device, filename, &buf, &len);
+		if (rc)
+			break;
+
+		conf_parse_buf(conf, buf, len);
+
+		talloc_free(buf);
+		talloc_free(state);
+		talloc_free(filename);
+		free(bls_entries[n]);
+	}
+
+	if (n > 0) {
+		device_handler_status_dev_info(dc->handler, dc->device,
+					       _("Scanning %s failed"),
+					       BLS_DIR);
+		do {
+			free(bls_entries[n]);
+		} while (n-- > 0);
+	}
+
+	free(bls_entries);
+err:
+	talloc_free(conf);
+	return rc;
+}