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]> Reviewed-by: Avnish Chouhan <[email protected]> Reviewed-by: Daniel Kiper <[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 c1a8a5117..7d4981d67 100644 --- a/util/grub-editenv.c +++ b/util/grub-editenv.c @@ -414,12 +414,35 @@ 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; @@ -430,15 +453,46 @@ 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 _______________________________________________ Grub-devel mailing list [email protected] https://lists.gnu.org/mailman/listinfo/grub-devel
