The gpt_sector=<sector> causes the GPT partition search to look at the
specified sector for a valid GPT header if the GPT is not found at the
beginning or the end of block device.
In particular this is needed for NVIDIA Tegra consumer-grade Android
devices in order to make them usable with the upstream kernel because
these devices use a proprietary / closed-source partition table format
for the EMMC and it's impossible to change the partition's format. Luckily
there is a GPT table in addition to the proprietary table, which is placed
in uncommon location of the EMMC storage and bootloader passes the
location to kernel using "gpt gpt_sector=<sector>" cmdline parameters.
This patch is based on the original work done by Colin Cross for the
downstream Android kernel.
Cc: Colin Cross <ccross@xxxxxxxxxxx>
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 5 +++++
block/partitions/efi.c | 15 +++++++++++++++
2 files changed, 20 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 50138e6826a1..ee4781daa379 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1382,6 +1382,11 @@
primary GPT is corrupted, it enables the backup/alternate
GPT to be used instead.
+ gpt_sector [EFI] Forces GPT partition search to look at the
+ specified sector for a valid GPT header if the GPT is
+ not found at the beginning or the end of the block
+ device.
+
grcan.enable0= [HW] Configuration of physical interface 0. Determines
the "Enable 0" bit of the configuration register.
Format: 0 | 1
diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index db2fef7dfc47..0c8926d76d7a 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -103,6 +103,17 @@ force_gpt_fn(char *str)
}
__setup("gpt", force_gpt_fn);
+/* This allows a kernel command line option 'gpt_sector=<sector>' to
+ * enable GPT header lookup at a non-standard location.
+ */
+static u64 force_gpt_sector;
+static int __init
+force_gpt_sector_fn(char *str)
+{
+ WARN_ON(kstrtoull(str, 10, &force_gpt_sector) < 0);
+ return 1;
+}
+__setup("gpt_sector=", force_gpt_sector_fn);
/**
* efi_crc32() - EFI version of crc32 function
@@ -621,6 +632,10 @@ static int find_valid_gpt(struct parsed_partitions *state, gpt_header **gpt,
if (!good_agpt && force_gpt)
good_agpt = is_gpt_valid(state, lastlba, &agpt, &aptes);
+ if (!good_agpt && force_gpt && force_gpt_sector)
+ good_agpt = is_gpt_valid(state, force_gpt_sector,
+ &agpt, &aptes);
+
/* The obviously unsuccessful case */
if (!good_pgpt && !good_agpt)
goto fail;
--
2.24.0
