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Fri, 23 Jan 2026 00:13:29 -0800 (PST) From: Coiby Xu To: kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org Cc: Arnaud Lefebvre , Baoquan he , Dave Young , Kairui Song , Pingfan Liu , Andrew Morton , Krzysztof Kozlowski , Rob Herring , Catalin Marinas , Will Deacon , Saravana Kannan , linux-kernel@vger.kernel.org (open list), devicetree@vger.kernel.org (open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE) Subject: [PATCH v3] arm64/kdump: pass dm-crypt keys to kdump kernel Date: Fri, 23 Jan 2026 16:13:25 +0800 Message-ID: <20260123081326.1362666-1-coxu@redhat.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" CONFIG_CRASH_DM_CRYPT has been introduced to support LUKS-encrypted device dump target by addressing two challenges [1], - Kdump kernel may not be able to decrypt the LUKS partition. For some machines, a system administrator may not have a chance to enter the password to decrypt the device in kdump initramfs after the 1st kernel crashes - LUKS2 by default use the memory-hard Argon2 key derivation function which is quite memory-consuming compared to the limited memory reserved for kdump. To also enable this feature for ARM64, we only need to add device tree property dmcryptkeys [2] as similar to elfcorehdr to pass the memory address of the stored info of dm-crypt keys to the kdump kernel. Since this property is only needed by the kdump kenrel, it won't be exposed to user space. [1] https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/ [2] https://github.com/devicetree-org/dt-schema/pull/181 Cc: Arnaud Lefebvre Cc: Baoquan he Cc: Dave Young Cc: Kairui Song Cc: Pingfan Liu Cc: Andrew Morton Cc: Krzysztof Kozlowski Cc: Rob Herring Signed-off-by: Coiby Xu --- v3 - Delete the property after reading it [Rob Herring] v2 - Krzysztof - Use imperative mood for commit message - Add dt-schema ABI Documentation=20 https://github.com/devicetree-org/dt-schema/pull/181 - Don't print dm-crypt keys address via pr_debug arch/arm64/kernel/machine_kexec_file.c | 9 +++++++++ drivers/of/fdt.c | 21 +++++++++++++++++++++ drivers/of/kexec.c | 19 +++++++++++++++++++ 3 files changed, 49 insertions(+) diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/mac= hine_kexec_file.c index 410060ebd86d..5f3bad8ca96d 100644 --- a/arch/arm64/kernel/machine_kexec_file.c +++ b/arch/arm64/kernel/machine_kexec_file.c @@ -134,6 +134,15 @@ int load_other_segments(struct kimage *image, =20 kexec_dprintk("Loaded elf core header at 0x%lx bufsz=3D0x%lx memsz=3D0x%= lx\n", image->elf_load_addr, kbuf.bufsz, kbuf.memsz); + + ret =3D crash_load_dm_crypt_keys(image); + + if (ret =3D=3D -ENOENT) { + kexec_dprintk("No dm crypt key to load\n"); + } else if (ret) { + pr_err("Failed to load dm crypt keys\n"); + goto out_err; + } } #endif =20 diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 331646d667b9..2967e4aff807 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -866,6 +866,26 @@ static void __init early_init_dt_check_for_elfcorehdr(= unsigned long node) elfcorehdr_addr, elfcorehdr_size); } =20 +static void __init early_init_dt_check_for_dmcryptkeys(unsigned long node) +{ + const char *prop_name =3D "linux,dmcryptkeys"; + const __be32 *prop; + + if (!IS_ENABLED(CONFIG_CRASH_DM_CRYPT)) + return; + + pr_debug("Looking for dmcryptkeys property... "); + + prop =3D of_get_flat_dt_prop(node, prop_name, NULL); + if (!prop) + return; + + dm_crypt_keys_addr =3D dt_mem_next_cell(dt_root_addr_cells, &prop); + + /* Property only accessible to crash dump kernel */ + fdt_delprop(initial_boot_params, node, prop_name); +} + static unsigned long chosen_node_offset =3D -FDT_ERR_NOTFOUND; =20 /* @@ -1097,6 +1117,7 @@ int __init early_init_dt_scan_chosen(char *cmdline) =20 early_init_dt_check_for_initrd(node); early_init_dt_check_for_elfcorehdr(node); + early_init_dt_check_for_dmcryptkeys(node); =20 rng_seed =3D of_get_flat_dt_prop(node, "rng-seed", &l); if (rng_seed && l > 0) { diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c index 1ee2d31816ae..4bfb1ea5744e 100644 --- a/drivers/of/kexec.c +++ b/drivers/of/kexec.c @@ -432,6 +432,25 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage= *image, if (ret) goto out; =20 + if (image->dm_crypt_keys_addr !=3D 0) { + ret =3D fdt_appendprop_addrrange(fdt, 0, chosen_node, + "linux,dmcryptkeys", + image->dm_crypt_keys_addr, + image->dm_crypt_keys_sz); + + if (ret) + goto out; + + /* + * Avoid dmcryptkeys from being stomped on in kdump kernel by + * setting up memory reserve map. + */ + ret =3D fdt_add_mem_rsv(fdt, image->dm_crypt_keys_addr, + image->dm_crypt_keys_sz); + if (ret) + goto out; + } + #ifdef CONFIG_CRASH_DUMP /* add linux,usable-memory-range */ ret =3D fdt_appendprop_addrrange(fdt, 0, chosen_node, base-commit: c072629f05d7bca1148ab17690d7922a31423984 --=20 2.52.0