On 2025-09-15 14:39, [email protected] wrote:
Message: 3
Date: Mon, 15 Sep 2025 17:08:41 +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 v2 2/9] util/grub-editenv: add fs_envblk open helper
Message-ID: <[email protected]>
This patch adds the logic to locate and open an environment block that
is stored in a reserved area on the device. It introduces the function
fs_envblk_open together with helper routines to read the block pointed
to by the env_block variable, and to create the block on disk when it
does not yet exist. When a block is created, the code records its
location inside the file based envblk by setting env_block in block
list
syntax of offset plus size in sectors.
The env_block variable acts as a link from the file envblk to the raw
disk region so that later runs of grub editenv can follow it and access
the external block. The helper is exposed through a small ops table
attached to fs_envblk so that later patches can call
fs_envblk->ops->open without touching core code again. At this stage
variables are still stored in the file envblk and no redirection has
been applied.
Signed-off-by: Michael Chang <[email protected]>
---
util/grub-editenv.c | 128 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 128 insertions(+)
diff --git a/util/grub-editenv.c b/util/grub-editenv.c
index 2302a6acf..4e5dffa86 100644
--- a/util/grub-editenv.c
+++ b/util/grub-editenv.c
@@ -130,12 +130,23 @@ struct fs_envblk_spec {
};
typedef struct fs_envblk_spec *fs_envblk_spec_t;
+static grub_envblk_t fs_envblk_open (grub_envblk_t envblk);
+
+struct fs_envblk_ops {
+ grub_envblk_t (*open) (grub_envblk_t);
+};
+
struct fs_envblk {
struct fs_envblk_spec *spec;
+ struct fs_envblk_ops *ops;
const char *dev;
};
typedef struct fs_envblk *fs_envblk_t;
+static struct fs_envblk_ops fs_envblk_ops = {
+ .open = fs_envblk_open
+};
+
static struct fs_envblk_spec fs_envblk_spec[] = {
{ "btrfs", ENV_BTRFS_OFFSET, GRUB_DISK_SECTOR_SIZE },
{ NULL, 0, 0 }
@@ -143,6 +154,122 @@ static struct fs_envblk_spec fs_envblk_spec[] = {
static fs_envblk_t fs_envblk = NULL;
+static int
+read_envblk_fs (const char *varname, const char *value, void
*hook_data)
+{
+ grub_envblk_t *p_envblk = (grub_envblk_t *)hook_data;
+ off_t off;
+ size_t sz;
+ char *p, *buf;
+ FILE *fp;
+
+ if (p_envblk == NULL || fs_envblk == NULL)
+ return 1;
+
+ if (strcmp (varname, "env_block") != 0)
+ return 0;
+
+ off = strtol (value, &p, 10);
+ if (*p == '+')
+ sz = strtol (p+1, &p, 10);
+ else
+ return 0;
+
+ if (*p != '\0' || sz == 0)
+ return 0;
+
+ off <<= GRUB_DISK_SECTOR_BITS;
+ sz <<= GRUB_DISK_SECTOR_BITS;
+
+ fp = grub_util_fopen (fs_envblk->dev, "rb");
+ if (! fp)
Hi Michael,
(fp == NULL) would be better here!
+ grub_util_error (_("cannot open `%s': %s"), fs_envblk->dev,
+ strerror (errno));
+
+ if (fseek (fp, off, SEEK_SET) < 0)
fclose (fp) seems missing here.
+ grub_util_error (_("cannot seek `%s': %s"), fs_envblk->dev,
+ strerror (errno));
+
+ buf = xmalloc (sz);
+ if ((fread (buf, 1, sz, fp)) != sz)
fclose (fp) seems missing as well as grub_free (buf).
+ grub_util_error (_("cannot read `%s': %s"), fs_envblk->dev,
+ strerror (errno));
+
+ fclose (fp);
+
+ *p_envblk = grub_envblk_open (buf, sz);
+
+ return 1;
+}
+
+static void
+create_envblk_fs (void)
+{
+ FILE *fp;
+ char *buf;
+ const char *device;
+ off_t offset;
+ size_t size;
+
+ if (fs_envblk == NULL)
+ return;
+
+ device = fs_envblk->dev;
+ offset = fs_envblk->spec->offset;
+ size = fs_envblk->spec->size;
+
+ fp = grub_util_fopen (device, "r+b");
+ if (fp == NULL)
+ grub_util_error (_("cannot open `%s': %s"), device, strerror
(errno));
+
+ buf = xmalloc (size);
+ memcpy (buf, GRUB_ENVBLK_SIGNATURE, sizeof (GRUB_ENVBLK_SIGNATURE) -
1);
+ memset (buf + sizeof (GRUB_ENVBLK_SIGNATURE) - 1, '#', size -
sizeof (GRUB_ENVBLK_SIGNATURE) + 1);
+
+ if (fseek (fp, offset, SEEK_SET) < 0)
fclose (fp) seems missing as well as grub_free (buf).
+ grub_util_error (_("cannot seek `%s': %s"), device, strerror
(errno));
+
+ if (fwrite (buf, 1, size, fp) != size)
fclose (fp) seems missing as well as grub_free (buf).
+ grub_util_error (_("cannot write to `%s': %s"), device, strerror
(errno));
+
+ grub_util_file_sync (fp);
+ free (buf);
+ fclose (fp);
+}
+
+static grub_envblk_t
+fs_envblk_open (grub_envblk_t envblk)
+{
+ grub_envblk_t envblk_fs = NULL;
+ char *val;
+ off_t offset;
+ size_t size;
+
+ if (envblk == NULL)
+ return NULL;
+
+ offset = fs_envblk->spec->offset;
+ size = fs_envblk->spec->size;
+
+ grub_envblk_iterate (envblk, &envblk_fs, read_envblk_fs);
+
+ if (envblk_fs && grub_envblk_size (envblk_fs) == size)
+ return envblk_fs;
+
+ create_envblk_fs ();
+
+ offset = offset >> GRUB_DISK_SECTOR_BITS;
+ size = (size + GRUB_DISK_SECTOR_SIZE - 1) >> GRUB_DISK_SECTOR_BITS;
+
+ val = xasprintf ("%ld+%lu", offset, size);
+ if (! grub_envblk_set (envblk, "env_block", val))
grub_free (val) missing here.
Thank you!
Regards,
Avnish Chouhan
+ grub_util_error ("%s", _("environment block too small"));
+ grub_envblk_iterate (envblk, &envblk_fs, read_envblk_fs);
+ free (val);
+
+ return envblk_fs;
+}
+
static grub_envblk_t
open_envblk_file (const char *name)
{
@@ -392,6 +519,7 @@ probe_fs_envblk (fs_envblk_spec_t spec)
fs_envblk = xmalloc (sizeof (fs_envblk_t));
fs_envblk->spec = p;
fs_envblk->dev = devname;
+ fs_envblk->ops = &fs_envblk_ops;
return fs_envblk;
}
}
--
2.51.0
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