Re: [PATCH v1] partitions/efi: Add 'gpt_sector' kernel cmdline parameter
From: Ard Biesheuvel <hidden>
Date: 2020-02-19 16:27:13
Also in:
linux-doc, linux-efi, linux-tegra, lkml
On Wed, 19 Feb 2020 at 17:25, Dmitry Osipenko [off-list ref] wrote:
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 <redacted> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Which block device is this parameter applied to?
quoted hunk ↗ jump to hunk
--- 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 | 1diff --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