This patch adds the function fs_envblk_write to update the reserved environment block on disk. The helper takes an in memory envblk buffer and writes it back to the device at the location defined by the fs_envblk specification. It performs size checks and uses file sync to ensure that the updated data is flushed.
The helper is also added into the fs_envblk ops table, together with the open helper from the previous patch. With this change the basic input and output path for an external environment block is complete. The choice of which variables should be written externally will be handled by later patches. Signed-off-by: Michael Chang <[email protected]> Reviewed-by: Neal Gompa <[email protected]> --- util/grub-editenv.c | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) diff --git a/util/grub-editenv.c b/util/grub-editenv.c index 829384392..450bb00a5 100644 --- a/util/grub-editenv.c +++ b/util/grub-editenv.c @@ -131,9 +131,11 @@ struct fs_envblk_spec { typedef struct fs_envblk_spec *fs_envblk_spec_t; static grub_envblk_t fs_envblk_open (grub_envblk_t envblk); +static void fs_envblk_write (grub_envblk_t envblk); struct fs_envblk_ops { grub_envblk_t (*open) (grub_envblk_t); + void (*write) (grub_envblk_t); }; struct fs_envblk { @@ -144,7 +146,8 @@ struct fs_envblk { typedef struct fs_envblk *fs_envblk_t; static struct fs_envblk_ops fs_envblk_ops = { - .open = fs_envblk_open + .open = fs_envblk_open, + .write = fs_envblk_write }; static struct fs_envblk_spec fs_envblk_spec[] = { @@ -358,6 +361,39 @@ write_envblk (const char *name, grub_envblk_t envblk) fclose (fp); } +static void +fs_envblk_write (grub_envblk_t envblk) +{ + FILE *fp; + const char *device; + off_t offset; + size_t size; + + if (envblk == NULL) + return; + + device = fs_envblk->dev; + offset = fs_envblk->spec->offset; + size = fs_envblk->spec->size; + + if (grub_envblk_size (envblk) > size) + grub_util_error ("%s", _("environment block too small")); + + fp = grub_util_fopen (device, "r+b"); + + if (fp == NULL) + grub_util_error (_("cannot open `%s': %s"), device, strerror (errno)); + + if (fseek (fp, offset, SEEK_SET) < 0) + grub_util_error (_("cannot seek `%s': %s"), device, strerror (errno)); + + if (fwrite (grub_envblk_buffer (envblk), 1, grub_envblk_size (envblk), fp) != grub_envblk_size (envblk)) + grub_util_error (_("cannot write to `%s': %s"), device, strerror (errno)); + + grub_util_file_sync (fp); + fclose (fp); +} + static void set_variables (const char *name, int argc, char *argv[]) { -- 2.51.0 _______________________________________________ Grub-devel mailing list [email protected] https://lists.gnu.org/mailman/listinfo/grub-devel
