From 56b221476d31310de485af26550c8651618832bb Mon Sep 17 00:00:00 2001 From: Michael Chang Date: Tue, 29 Oct 2024 11:54:28 +0800 Subject: [PATCH] kern/main: Fix cmdpath in root directory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The "cmdpath" environment variable is set at startup to the location from which the grub image is loaded. It includes a device part and, optionally, an absolute directory name if the grub image is booted as a file in a local file-system directory, or in a remote server directory, like TFTP. This entire process relies on firmware to provide the correct device path of the booted image. We encountered an issue when the image is booted from the root directory, where the absolute directory name "/" is discarded. This makes it unclear whether the root path was missing in the firmware provided device path or if it is simply the root directory. This ambiguity can cause confusion in custom scripts, potentially causing them to interpret firmware data incorrectly and trigger unintended fallback measures. This patch fixes the problem by properly assigning the "fwpath" returned by "grub_machine_get_bootlocation()" to "cmdpath". The fix is based on the fact that fwpath is NULL if the firmware didn’t provide a path part or an NUL character, "", if it represents the root directory. With this, it becomes possible to clearly distinguish: - cmdpath=(hd0,1) - Either the image is booted from the first (raw) partition, or the firmware failed to provide the path part. - cmdpath=(hd0,1)/ - The image is booted from the root directory in the first partition. As a side note, the fix is similar to [1], but without the renaming part. [1] https://mail.gnu.org/archive/html/grub-devel/2024-10/msg00155.html Signed-off-by: Michael Chang --- grub-core/kern/main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/grub-core/kern/main.c b/grub-core/kern/main.c index ef3b3756d..f9ab12c74 100644 --- a/grub-core/kern/main.c +++ b/grub-core/kern/main.c @@ -136,7 +136,11 @@ grub_set_prefix_and_root (void) { char *cmdpath; - cmdpath = grub_xasprintf ("(%s)%s", fwdevice, fwpath ? : ""); + if (fwpath && *fwpath == '\0') + cmdpath = grub_xasprintf ("(%s)/", fwdevice); + else + cmdpath = grub_xasprintf ("(%s)%s", fwdevice, fwpath ? : ""); + if (cmdpath) { grub_env_set ("cmdpath", cmdpath); -- 2.47.0