Calling bootm on an x86 kernel image that lacks an EFI stub will result
in a "no image handler found for image type MBR sector", which can be
very confusing.
Improve upon this by directly suggesting that the kernel's
CONFIG_EFI_STUB option needs to be enabled, so the image has the
expected PE magic (and the EFI stub code that comes with it).
Cc: cybin <info@xxxxxxxxxxxxxxx>
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
efi/payload/image.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/efi/payload/image.c b/efi/payload/image.c
index 0795010cd9d2..6a41338f2a2f 100644
--- a/efi/payload/image.c
+++ b/efi/payload/image.c
@@ -337,6 +337,26 @@ static struct binfmt_hook binfmt_efi_hook = {
.hook = efi_execute,
};
+static int do_bootm_mbr(struct image_data *data)
+{
+ /* On x86, Linux kernel images have a MBR magic at the end of
+ * the first 512 byte sector and a PE magic if they're EFI-stubbed.
+ * The PE magic has precedence over the MBR, so if we arrive in
+ * this boot handler, the kernel has no EFI stub.
+ *
+ * Print a descriptive error message instead of "no image handler
+ * found for image type MBR sector".
+ */
+ pr_err("Can't boot MBR sector: Is CONFIG_EFI_STUB disabled in your Linux kernel config?\n");
+ return -ENOSYS;
+}
+
+static struct image_handler non_efi_handle_linux_x86 = {
+ .name = "non-EFI x86 Linux Image",
+ .bootm = do_bootm_mbr,
+ .filetype = filetype_mbr,
+};
+
static struct binfmt_hook binfmt_arm64_efi_hook = {
.type = filetype_arm64_efi_linux_image,
.hook = efi_execute,
@@ -350,6 +370,9 @@ static int efi_register_image_handler(void)
if (IS_ENABLED(CONFIG_CPU_V8))
binfmt_register(&binfmt_arm64_efi_hook);
+ if (IS_ENABLED(CONFIG_X86))
+ register_image_handler(&non_efi_handle_linux_x86);
+
return 0;
}
late_efi_initcall(efi_register_image_handler);
--
2.39.2
