discover/grub: Improve BLS grub environment variables expansion

The fields from a BootLoaderSpec file can contain environment variables,
in GRUB 2 these are show verbatim and are evaluated later when an entry
is selected. But on Petitboot these have to be expanded before creating
the GRUB 2 resources and show in the UI the values after the evaluation.

The current blscfg handler had a very limited support for variables, it
only had support for the options field and also didn't take into account
that variables could be mixed with literal values.

So for example the following fields were not expanded correctly:

  linux   $bootprefix/vmlinuz

  options $kernelopts foo=bar

  options foo=bar $kernelopts

  options $kernelopts $debugopts

Also change some of the tests to cover mixing variables and literals.

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

diff --git a/discover/grub2/blscfg.c b/discover/grub2/blscfg.c
index a3813064a0a3daa30d47c168e4a54081e5b2c902..d4754aa363dfa0812d2feb9b7ced5be6e03b7aa9 100644 (file)
--- a/discover/grub2/blscfg.c
+++ b/discover/grub2/blscfg.c
@@ -2,6 +2,7 @@
 #define _GNU_SOURCE
 
 #include <assert.h>
+#include <ctype.h>
 #include <stdlib.h>
 #include <string.h>
 #include <dirent.h>
@@ -34,54 +35,106 @@ struct bls_state {
        const char *dtb;
 };
 
+static char *field_append(struct bls_state *state, int type, char *buffer,
+                         char *start, char *end)
+{
+       char *temp = talloc_strndup(state, start, end - start + 1);
+       const char *field = temp;
+
+       if (type == GRUB2_WORD_VAR) {
+               field = script_env_get(state->script, temp);
+               if (!field)
+                       return buffer;
+       }
+
+       if (!buffer)
+               buffer = talloc_strdup(state->opt, field);
+       else
+               buffer = talloc_asprintf_append(buffer, "%s", field);
+
+       return buffer;
+}
+
+static char *expand_field(struct bls_state *state, char *value)
+{
+       char *buffer = NULL;
+       char *start = value;
+       char *end = value;
+       int type = GRUB2_WORD_TEXT;
+
+       while (*value) {
+               if (*value == '$') {
+                       if (start != end) {
+                               buffer = field_append(state, type, buffer,
+                                                     start, end);
+                               if (!buffer)
+                                       return NULL;
+                       }
+
+                       type = GRUB2_WORD_VAR;
+                       start = value + 1;
+               } else if (type == GRUB2_WORD_VAR) {
+                       if (!isalnum(*value) && *value != '_') {
+                               buffer = field_append(state, type, buffer,
+                                                     start, end);
+                               type = GRUB2_WORD_TEXT;
+                               start = value;
+                       }
+               }
+
+               end = value;
+               value++;
+       }
+
+       if (start != end) {
+               buffer = field_append(state, type, buffer,
+                                     start, end);
+               if (!buffer)
+                       return NULL;
+       }
+
+       return buffer;
+}
+
 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);
+               state->title = expand_field(state, value);
                return;
        }
 
        if (streq(name, "version")) {
-               state->version = talloc_strdup(state, value);
+               state->version = expand_field(state, value);
                return;
        }
 
        if (streq(name, "machine-id")) {
-               state->machine_id = talloc_strdup(state, value);
+               state->machine_id = expand_field(state, value);
                return;
        }
 
        if (streq(name, "linux")) {
-               state->image = talloc_strdup(state, value);
+               state->image = expand_field(state, value);
                return;
        }
 
        if (streq(name, "initrd")) {
-               state->initrd = talloc_strdup(state, value);
+               state->initrd = expand_field(state, value);
                return;
        }
 
        if (streq(name, "devicetree")) {
-               state->dtb = talloc_strdup(state, value);
+               state->dtb = expand_field(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);
-               }
+               option->boot_args = expand_field(state, value);
                return;
        }
 }

diff --git a/test/parser/test-grub2-blscfg-multiple-bls.c b/test/parser/test-grub2-blscfg-multiple-bls.c
index 94f40d191fa7251eccd7c044e9f162a1aa0aa5f1..d15fb24fd7ef3f84cfdbd0252e1db5bed2fd1655 100644 (file)
--- a/test/parser/test-grub2-blscfg-multiple-bls.c
+++ b/test/parser/test-grub2-blscfg-multiple-bls.c
@@ -1,6 +1,7 @@
 #include "parser-test.h"
 
 #if 0 /* PARSER_EMBEDDED_CONFIG */
+set os_name=Fedora
 blscfg
 #endif
 
@@ -13,14 +14,14 @@ void run_test(struct parser_test *test)
 
        test_add_file_string(test, test->ctx->device,
                             "/loader/entries/6c063c8e48904f2684abde8eea303f41-4.15.2-302.fc28.x86_64.conf",
-                            "title Fedora (4.15.2-302.fc28.x86_64) 28 (Twenty Eight)\n"
+                            "title $os_name (4.15.2-302.fc28.x86_64) 28 (Twenty Eight)\n"
                             "linux /vmlinuz-4.15.2-302.fc28.x86_64\n"
                             "initrd /initramfs-4.15.2-302.fc28.x86_64.img\n"
                             "options root=/dev/mapper/fedora-root ro rd.lvm.lv=fedora/root\n\n");
 
        test_add_file_string(test, test->ctx->device,
                             "/loader/entries/6c063c8e48904f2684abde8eea303f41-4.14.18-300.fc28.x86_64.conf",
-                            "title Fedora (4.14.18-300.fc28.x86_64) 28 (Twenty Eight)\n"
+                            "title $os_name (4.14.18-300.fc28.x86_64) 28 (Twenty Eight)\n"
                             "linux /vmlinuz-4.14.18-300.fc28.x86_64\n"
                             "initrd /initramfs-4.14.18-300.fc28.x86_64.img\n"
                             "options root=/dev/mapper/fedora-root ro rd.lvm.lv=fedora/root\n");

diff --git a/test/parser/test-grub2-blscfg-opts-grubenv.c b/test/parser/test-grub2-blscfg-opts-grubenv.c
index 544a5de4d23abcad407a33dbf844806e5a81e351..2dffd1b730c938c6c1b5fc6c3f6d004156153d0a 100644 (file)
--- a/test/parser/test-grub2-blscfg-opts-grubenv.c
+++ b/test/parser/test-grub2-blscfg-opts-grubenv.c
@@ -22,7 +22,7 @@ void run_test(struct parser_test *test)
                             "title Fedora (4.15.2-302.fc28.x86_64) 28 (Twenty Eight)\n"
                             "linux /vmlinuz-4.15.2-302.fc28.x86_64\n"
                             "initrd /initramfs-4.15.2-302.fc28.x86_64.img\n"
-                            "options $kernelopts\n");
+                            "options $kernelopts debug\n");
 
        test_read_conf_embedded(test, "/boot/grub2/grub.cfg");
 
@@ -32,5 +32,5 @@ void run_test(struct parser_test *test)
 
        opt = get_boot_option(ctx, 0);
 
-       check_args(opt, "root=/dev/mapper/fedora-root ro rd.lvm.lv=fedora/root");
+       check_args(opt, "root=/dev/mapper/fedora-root ro rd.lvm.lv=fedora/root debug");
 }