On 2025-10-09 12:50, [email protected] wrote:
Reviewed-by: Avnish Chouhan <[email protected]>
Message: 3
Date: Thu, 9 Oct 2025 15:18:40 +0800
From: Michael Chang <[email protected]>
To: The development of GNU GRUB <[email protected]>
Cc: Neal Gompa <[email protected]>, Marta Lewandowska
<[email protected]>
Subject: [PATCH v4 07/12] util/grub-editenv: wire set_variables to
optional fs_envblk
Message-ID: <[email protected]>
This patch changes set_variables() so that it can use an external
environment block when one is present. The variable next_entry is
written into the external block, env_block is treated as read only, and
all other variables are written into the normal file based envblk.
A cleanup step is added to handle cases where GRUB at runtime writes
variables into the external block because file based updates are not
safe on a copy on write filesystem such as Btrfs. For example, the
savedefault command can update saved_entry, and on Btrfs GRUB will
place
that update in the external block instead of the file envblk. If an
older copy remains in the external block, it would override the newer
value from the file envblk when GRUB first loads the file and then
applies the external block on top of it. To avoid this, whenever a
variable is updated in the file envblk, any same named key in the
external block is deleted.
Signed-off-by: Michael Chang <[email protected]>
Reviewed-by: Neal Gompa <[email protected]>
---
util/grub-editenv.c | 58 +++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 2 deletions(-)
diff --git a/util/grub-editenv.c b/util/grub-editenv.c
index 42a0c63f8..beb2dd4fc 100644
--- a/util/grub-editenv.c
+++ b/util/grub-editenv.c
@@ -402,12 +402,35 @@ fs_envblk_write (grub_envblk_t envblk)
fclose (fp);
}
+struct var_lookup_ctx {
+ const char *varname;
+ bool found;
+};
+typedef struct var_lookup_ctx var_lookup_ctx_t;
+
+static int
+var_lookup_iter (const char *varname, const char *value __attribute__
((unused)), void *hook_data)
+{
+ var_lookup_ctx_t *ctx = (var_lookup_ctx_t *) hook_data;
+
+ if (grub_strcmp (ctx->varname, varname) == 0)
+ {
+ ctx->found = true;
+ return 1;
+ }
+ return 0;
+}
+
static void
set_variables (const char *name, int argc, char *argv[])
{
grub_envblk_t envblk;
+ grub_envblk_t envblk_on_block = NULL;
envblk = open_envblk_file (name);
+ if (fs_envblk != NULL)
+ envblk_on_block = fs_envblk->ops->open (envblk);
+
while (argc)
{
char *p;
@@ -418,15 +441,46 @@ set_variables (const char *name, int argc, char
*argv[])
*(p++) = 0;
- if (! grub_envblk_set (envblk, argv[0], p))
- grub_util_error ("%s", _("environment block too small"));
+ if ((strcmp (argv[0], "next_entry") == 0) && envblk_on_block !=
NULL)
+ {
+ if (grub_envblk_set (envblk_on_block, argv[0], p) == 0)
+ grub_util_error ("%s", _("environment block too small"));
+ goto next;
+ }
+
+ if (strcmp (argv[0], "env_block") == 0)
+ {
+ grub_util_warn (_("can't set env_block as it's read-only"));
+ goto next;
+ }
+
+ if (grub_envblk_set (envblk, argv[0], p) == 0)
+ grub_util_error ("%s", _("environment block too small"));
+ if (envblk_on_block != NULL)
+ {
+ var_lookup_ctx_t ctx = {
+ .varname = argv[0],
+ .found = false
+ };
+
+ grub_envblk_iterate (envblk_on_block, &ctx, var_lookup_iter);
+ if (ctx.found == true)
+ grub_envblk_delete (envblk_on_block, argv[0]);
+ }
+ next:
argc--;
argv++;
}
write_envblk (name, envblk);
grub_envblk_close (envblk);
+
+ if (envblk_on_block != NULL)
+ {
+ fs_envblk->ops->write (envblk_on_block);
+ grub_envblk_close (envblk_on_block);
+ }
}
static void
--
2.51.0
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