[PATCH v5 0/3] kdump: Enable LUKS-encrypted dump target support in ARM64 and PowerPC

[PATCH v5 0/3] kdump: Enable LUKS-encrypted dump target support in ARM64 and PowerPC

[Coiby Xu]

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 and PowerPC, we need to add a
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.

[1] https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/
[2] https://github.com/devicetree-org/dt-schema/pull/181


v5
- Improve commit msg [Christophe]
- Fix a compiling error found by kernel test robot

v4
- Make arch-specific code more succinct by printing more logs in
  arch-independent code [Will Deacon]  

- Also use device tree for PowerPC to pass memory address of dm-crypt
  keys info
  - powerpc v2 patch that passes the dmcryptkeys kernel cmdline
    parameter:
    https://lore.kernel.org/all/20260106074039.564707-1-coxu@redhat.com/

v3
- Delete the property after reading it [Rob Herring]

v2
- Krzysztof
  - Use imperative mood for commit message
  - Add dt-schema ABI Documentation 
    https://github.com/devicetree-org/dt-schema/pull/181
- Don't print dm-crypt keys address via pr_debug

Coiby Xu (3):
  crash_dump/dm-crypt: Don't print in arch-specific code
  crash: Align the declaration of crash_load_dm_crypt_keys with
    CONFIG_CRASH_DM_CRYPT
  arm64,ppc64le/kdump: pass dm-crypt keys to kdump kernel

 arch/arm64/kernel/machine_kexec_file.c |  4 ++++
 arch/powerpc/kexec/elf_64.c            |  4 ++++
 arch/x86/kernel/kexec-bzimage64.c      |  6 +-----
 drivers/of/fdt.c                       | 21 +++++++++++++++++++++
 drivers/of/kexec.c                     | 19 +++++++++++++++++++
 include/linux/crash_core.h             | 14 +++++++-------
 kernel/crash_dump_dm_crypt.c           |  7 +++++--
 7 files changed, 61 insertions(+), 14 deletions(-)


base-commit: 7dff99b354601dd01829e1511711846e04340a69
-- 
2.53.0

[PATCH v5 1/3] crash_dump/dm-crypt: Don't print in arch-specific code

[Coiby Xu]

When the vmcore dumping target is not a LUKS-encrypted target, it's
expected that there is no dm-crypt key thus no need to return -ENOENT.
Also print more logs in crash_load_dm_crypt_keys. The benefit is
arch-specific code can be more succinct.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 6 +-----
 kernel/crash_dump_dm_crypt.c      | 7 +++++--
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 5630c7dca1f3..7e980ea49d8d 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -525,12 +525,8 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 		if (ret)
 			return ERR_PTR(ret);
 		ret = crash_load_dm_crypt_keys(image);
-		if (ret == -ENOENT) {
-			kexec_dprintk("No dm crypt key to load\n");
-		} else if (ret) {
-			pr_err("Failed to load dm crypt keys\n");
+		if (ret)
 			return ERR_PTR(ret);
-		}
 		if (image->dm_crypt_keys_addr &&
 		    cmdline_len + MAX_ELFCOREHDR_STR_LEN + MAX_DMCRYPTKEYS_STR_LEN >
 			    header->cmdline_size) {
diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
index 1f4067fbdb94..2f7b42b09673 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -414,14 +414,16 @@ int crash_load_dm_crypt_keys(struct kimage *image)
 
 	if (key_count <= 0) {
 		kexec_dprintk("No dm-crypt keys\n");
-		return -ENOENT;
+		return 0;
 	}
 
 	if (!is_dm_key_reused) {
 		image->dm_crypt_keys_addr = 0;
 		r = build_keys_header();
-		if (r)
+		if (r) {
+			pr_err("Failed to build dm-crypt keys header, ret=%d\n", r);
 			return r;
+		}
 	}
 
 	kbuf.buffer = keys_header;
@@ -432,6 +434,7 @@ int crash_load_dm_crypt_keys(struct kimage *image)
 	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 	r = kexec_add_buffer(&kbuf);
 	if (r) {
+		pr_err("Failed to call kexec_add_buffer, ret=%d\n", r);
 		kvfree((void *)kbuf.buffer);
 		return r;
 	}
-- 
2.53.0

[PATCH v5 2/3] crash: Align the declaration of crash_load_dm_crypt_keys with CONFIG_CRASH_DM_CRYPT

[Coiby Xu]

This will prevent a compiling failure when CONFIG_CRASH_DUMP is enabled
but CONFIG_CRASH_DM_CRYPT is disabled,

       arch/powerpc/kexec/elf_64.c: In function 'elf64_load':
    >> arch/powerpc/kexec/elf_64.c:82:23: error: implicit declaration of function 'crash_load_dm_crypt_keys' [-Werror=implicit-function-declaration]
          82 |                 ret = crash_load_dm_crypt_keys(image);
             |                       ^~~~~~~~~~~~~~~~~~~~~~~~
       cc1: some warnings being treated as errors

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602120648.RgQALnnI-lkp@intel.com/
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 include/linux/crash_core.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d35726d6a415..c1dee3f971a9 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -34,13 +34,6 @@ static inline void arch_kexec_protect_crashkres(void) { }
 static inline void arch_kexec_unprotect_crashkres(void) { }
 #endif
 
-#ifdef CONFIG_CRASH_DM_CRYPT
-int crash_load_dm_crypt_keys(struct kimage *image);
-ssize_t dm_crypt_keys_read(char *buf, size_t count, u64 *ppos);
-#else
-static inline int crash_load_dm_crypt_keys(struct kimage *image) {return 0; }
-#endif
-
 #ifndef arch_crash_handle_hotplug_event
 static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }
 #endif
@@ -96,4 +89,11 @@ static inline void crash_save_cpu(struct pt_regs *regs, int cpu) {};
 static inline int kimage_crash_copy_vmcoreinfo(struct kimage *image) { return 0; };
 #endif /* CONFIG_CRASH_DUMP*/
 
+#ifdef CONFIG_CRASH_DM_CRYPT
+int crash_load_dm_crypt_keys(struct kimage *image);
+ssize_t dm_crypt_keys_read(char *buf, size_t count, u64 *ppos);
+#else
+static inline int crash_load_dm_crypt_keys(struct kimage *image) {return 0; }
+#endif
+
 #endif /* LINUX_CRASH_CORE_H */
-- 
2.53.0

[PATCH v5 3/3] arm64,ppc64le/kdump: pass dm-crypt keys to kdump kernel

[Coiby Xu]

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 and PowerPC, the missing piece is
to let the kdump kernel know where to find the dm-crypt keys which are
randomly stored in memory reserved for kdump. Introduce a new 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 kernel, 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 <arnaud.lefebvre@clever-cloud.com>
Cc: Baoquan he <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Thomas Staudt <tstaudt@de.ibm.com>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 arch/arm64/kernel/machine_kexec_file.c |  4 ++++
 arch/powerpc/kexec/elf_64.c            |  4 ++++
 drivers/of/fdt.c                       | 21 +++++++++++++++++++++
 drivers/of/kexec.c                     | 19 +++++++++++++++++++
 4 files changed, 48 insertions(+)

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index fba260ad87a9..e31fabed378a 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -134,6 +134,10 @@ int load_other_segments(struct kimage *image,
 
 		kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 			      image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
+
+		ret = crash_load_dm_crypt_keys(image);
+		if (ret)
+			goto out_err;
 	}
 #endif
 
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 5d6d616404cf..ea50a072debf 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -79,6 +79,10 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 			goto out;
 		}
 
+		ret = crash_load_dm_crypt_keys(image);
+		if (ret)
+			goto out;
+
 		/* Setup cmdline for kdump kernel case */
 		modified_cmdline = setup_kdump_cmdline(image, cmdline,
 						       cmdline_len);
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);
 }
 
+static void __init early_init_dt_check_for_dmcryptkeys(unsigned long node)
+{
+	const char *prop_name = "linux,dmcryptkeys";
+	const __be32 *prop;
+
+	if (!IS_ENABLED(CONFIG_CRASH_DM_CRYPT))
+		return;
+
+	pr_debug("Looking for dmcryptkeys property... ");
+
+	prop = of_get_flat_dt_prop(node, prop_name, NULL);
+	if (!prop)
+		return;
+
+	dm_crypt_keys_addr = 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 = -FDT_ERR_NOTFOUND;
 
 /*
@@ -1097,6 +1117,7 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 
 	early_init_dt_check_for_initrd(node);
 	early_init_dt_check_for_elfcorehdr(node);
+	early_init_dt_check_for_dmcryptkeys(node);
 
 	rng_seed = 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 c4cf3552c018..fbd253f0d3c5 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -423,6 +423,25 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
 		if (ret)
 			goto out;
 
+		if (image->dm_crypt_keys_addr != 0) {
+			ret = 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 = 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 = fdt_appendprop_addrrange(fdt, 0, chosen_node,
-- 
2.53.0

Re: [PATCH v5 0/3] kdump: Enable LUKS-encrypted dump target support in ARM64 and PowerPC

[Andrew Morton]

On Wed, 25 Feb 2026 14:03:43 +0800 Coiby Xu <coxu@redhat.com> wrote:

> 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 and PowerPC, we need to add a
> 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.

We don't have any ack/review tags for this series.  Could someone
please help out?