[PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Coiby Xu]

Based on the CONFIG_CRASH_DM_CRYPT feature, this patch adds
LUKS-encrypted device dump target support to PowerPC 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.

1st kernel will build up the kernel command parameter dmcryptkeys 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/

Cc: Thomas Staudt <tstaudt@de.ibm.com>
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>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 arch/powerpc/include/asm/kexec.h |  3 ++-
 arch/powerpc/kexec/elf_64.c      | 26 +++++++++++++++++++++++++-
 arch/powerpc/kexec/file_load.c   | 19 +++++++++++--------
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index bd4a6c42a5f3..f3d098d543b4 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -80,7 +80,8 @@ struct kimage_arch {
 };
 
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
-			  unsigned long cmdline_len);
+			  unsigned long cmdline_len,
+			  char *name, unsigned long addr);
 int setup_purgatory(struct kimage *image, const void *slave_code,
 		    const void *fdt, unsigned long kernel_load_addr,
 		    unsigned long fdt_load_addr);
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 5d6d616404cf..57cb3361d91b 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -81,13 +81,37 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 
 		/* Setup cmdline for kdump kernel case */
 		modified_cmdline = setup_kdump_cmdline(image, cmdline,
-						       cmdline_len);
+						       cmdline_len,
+						       "elfcorehdr",
+						       image->elf_load_addr);
 		if (!modified_cmdline) {
 			pr_err("Setting up cmdline for kdump kernel failed\n");
 			ret = -EINVAL;
 			goto out;
 		}
 		cmdline = modified_cmdline;
+		cmdline_len = strlen(cmdline) + 1;
+
+		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");
+			return ERR_PTR(ret);
+		}
+
+		if (image->dm_crypt_keys_addr != 0) {
+			modified_cmdline = setup_kdump_cmdline(image, cmdline,
+							       cmdline_len,
+							       "dmcryptkeys",
+							       image->dm_crypt_keys_addr);
+			if (!modified_cmdline) {
+				pr_err("Setting up cmdline for kdump kernel failed\n");
+				ret = -EINVAL;
+				goto out;
+			}
+			cmdline = modified_cmdline;
+		}
 	}
 
 	if (initrd != NULL) {
diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
index 4284f76cbef5..e1c08050286d 100644
--- a/arch/powerpc/kexec/file_load.c
+++ b/arch/powerpc/kexec/file_load.c
@@ -23,38 +23,41 @@
 #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
 
 /**
- * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
+ * setup_kdump_cmdline - Prepend "<name>=<addr> " to command line
  *                       of kdump kernel for exporting the core.
  * @image:               Kexec image
  * @cmdline:             Command line parameters to update.
  * @cmdline_len:         Length of the cmdline parameters.
+ * @name:                Name e.g elfcorehdr.
+ * @addr:                Memory address.
  *
  * kdump segment must be setup before calling this function.
  *
  * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
  */
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
-			  unsigned long cmdline_len)
+			  unsigned long cmdline_len,
+			  char *name, unsigned long addr)
 {
-	int elfcorehdr_strlen;
+	unsigned long parameter_len;
 	char *cmdline_ptr;
 
 	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
 	if (!cmdline_ptr)
 		return NULL;
 
-	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
-				    image->elf_load_addr);
+	parameter_len = sprintf(cmdline_ptr, "%s=0x%lx ", name, addr);
 
-	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
-		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
+	if (parameter_len + cmdline_len > COMMAND_LINE_SIZE) {
+		pr_err("Appending %s=<addr> exceeds cmdline size\n", name);
 		kfree(cmdline_ptr);
 		return NULL;
 	}
 
-	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
+	memcpy(cmdline_ptr + parameter_len, cmdline, cmdline_len);
 	// Ensure it's nul terminated
 	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
+	kfree(cmdline);
 	return cmdline_ptr;
 }
 

base-commit: ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1
-- 
2.52.0

Re: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[kernel test robot]

Hi Coiby,

kernel test robot noticed the following build errors:

[auto build test ERROR on ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1]

url:    https://github.com/intel-lab-lkp/linux/commits/Coiby-Xu/powerpc-kdump-pass-dm-crypt-keys-to-kdump-kernel/20251226-220726
base:   ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1
patch link:    https://lore.kernel.org/r/20251226140636.1378505-1-coxu%40redhat.com
patch subject: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel
config: powerpc64-randconfig-001-20251227 (https://download.01.org/0day-ci/archive/20251227/202512272218.ghBaSjzO-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 4ef602d446057dabf5f61fb221669ecbeda49279)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251227/202512272218.ghBaSjzO-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512272218.ghBaSjzO-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/powerpc/kexec/elf_64.c:95:9: error: call to undeclared function 'crash_load_dm_crypt_keys'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      95 |                 ret = crash_load_dm_crypt_keys(image);
         |                       ^
   1 error generated.


vim +/crash_load_dm_crypt_keys +95 arch/powerpc/kexec/elf_64.c

    27	
    28	static void *elf64_load(struct kimage *image, char *kernel_buf,
    29				unsigned long kernel_len, char *initrd,
    30				unsigned long initrd_len, char *cmdline,
    31				unsigned long cmdline_len)
    32	{
    33		int ret;
    34		unsigned long kernel_load_addr;
    35		unsigned long initrd_load_addr = 0, fdt_load_addr;
    36		void *fdt;
    37		const void *slave_code;
    38		struct elfhdr ehdr;
    39		char *modified_cmdline = NULL;
    40		struct crash_mem *rmem = NULL;
    41		struct kexec_elf_info elf_info;
    42		struct kexec_buf kbuf = { .image = image, .buf_min = 0,
    43					  .buf_max = ppc64_rma_size };
    44		struct kexec_buf pbuf = { .image = image, .buf_min = 0,
    45					  .buf_max = ppc64_rma_size, .top_down = true,
    46					  .mem = KEXEC_BUF_MEM_UNKNOWN };
    47	
    48		ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info);
    49		if (ret)
    50			return ERR_PTR(ret);
    51	
    52		if (IS_ENABLED(CONFIG_CRASH_DUMP) && image->type == KEXEC_TYPE_CRASH) {
    53			/* min & max buffer values for kdump case */
    54			kbuf.buf_min = pbuf.buf_min = crashk_res.start;
    55			kbuf.buf_max = pbuf.buf_max =
    56					((crashk_res.end < ppc64_rma_size) ?
    57					 crashk_res.end : (ppc64_rma_size - 1));
    58		}
    59	
    60		ret = kexec_elf_load(image, &ehdr, &elf_info, &kbuf, &kernel_load_addr);
    61		if (ret)
    62			goto out;
    63	
    64		kexec_dprintk("Loaded the kernel at 0x%lx\n", kernel_load_addr);
    65	
    66		ret = kexec_load_purgatory(image, &pbuf);
    67		if (ret) {
    68			pr_err("Loading purgatory failed.\n");
    69			goto out;
    70		}
    71	
    72		kexec_dprintk("Loaded purgatory at 0x%lx\n", pbuf.mem);
    73	
    74		/* Load additional segments needed for panic kernel */
    75		if (IS_ENABLED(CONFIG_CRASH_DUMP) && image->type == KEXEC_TYPE_CRASH) {
    76			ret = load_crashdump_segments_ppc64(image, &kbuf);
    77			if (ret) {
    78				pr_err("Failed to load kdump kernel segments\n");
    79				goto out;
    80			}
    81	
    82			/* Setup cmdline for kdump kernel case */
    83			modified_cmdline = setup_kdump_cmdline(image, cmdline,
    84							       cmdline_len,
    85							       "elfcorehdr",
    86							       image->elf_load_addr);
    87			if (!modified_cmdline) {
    88				pr_err("Setting up cmdline for kdump kernel failed\n");
    89				ret = -EINVAL;
    90				goto out;
    91			}
    92			cmdline = modified_cmdline;
    93			cmdline_len = strlen(cmdline) + 1;
    94	
  > 95			ret = crash_load_dm_crypt_keys(image);
    96			if (ret == -ENOENT) {
    97				kexec_dprintk("No dm crypt key to load\n");
    98			} else if (ret) {
    99				pr_err("Failed to load dm crypt keys\n");
   100				return ERR_PTR(ret);
   101			}
   102	
   103			if (image->dm_crypt_keys_addr != 0) {
   104				modified_cmdline = setup_kdump_cmdline(image, cmdline,
   105								       cmdline_len,
   106								       "dmcryptkeys",
   107								       image->dm_crypt_keys_addr);
   108				if (!modified_cmdline) {
   109					pr_err("Setting up cmdline for kdump kernel failed\n");
   110					ret = -EINVAL;
   111					goto out;
   112				}
   113				cmdline = modified_cmdline;
   114			}
   115		}
   116	
   117		if (initrd != NULL) {
   118			kbuf.buffer = initrd;
   119			kbuf.bufsz = kbuf.memsz = initrd_len;
   120			kbuf.buf_align = PAGE_SIZE;
   121			kbuf.top_down = false;
   122			kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
   123			ret = kexec_add_buffer(&kbuf);
   124			if (ret)
   125				goto out;
   126			initrd_load_addr = kbuf.mem;
   127	
   128			kexec_dprintk("Loaded initrd at 0x%lx\n", initrd_load_addr);
   129		}
   130	
   131		ret = get_reserved_memory_ranges(&rmem);
   132		if (ret)
   133			goto out;
   134	
   135		fdt = of_kexec_alloc_and_setup_fdt(image, initrd_load_addr,
   136						   initrd_len, cmdline,
   137						   kexec_extra_fdt_size_ppc64(image, rmem));
   138		if (!fdt) {
   139			pr_err("Error setting up the new device tree.\n");
   140			ret = -EINVAL;
   141			goto out;
   142		}
   143	
   144		ret = setup_new_fdt_ppc64(image, fdt, rmem);
   145		if (ret)
   146			goto out_free_fdt;
   147	
   148		if (!IS_ENABLED(CONFIG_CRASH_HOTPLUG) || image->type != KEXEC_TYPE_CRASH)
   149			fdt_pack(fdt);
   150	
   151		kbuf.buffer = fdt;
   152		kbuf.bufsz = kbuf.memsz = fdt_totalsize(fdt);
   153		kbuf.buf_align = PAGE_SIZE;
   154		kbuf.top_down = true;
   155		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
   156		ret = kexec_add_buffer(&kbuf);
   157		if (ret)
   158			goto out_free_fdt;
   159	
   160		/* FDT will be freed in arch_kimage_file_post_load_cleanup */
   161		image->arch.fdt = fdt;
   162	
   163		fdt_load_addr = kbuf.mem;
   164	
   165		kexec_dprintk("Loaded device tree at 0x%lx\n", fdt_load_addr);
   166	
   167		slave_code = elf_info.buffer + elf_info.proghdrs[0].p_offset;
   168		ret = setup_purgatory_ppc64(image, slave_code, fdt, kernel_load_addr,
   169					    fdt_load_addr);
   170		if (ret)
   171			pr_err("Error setting up the purgatory.\n");
   172	
   173		goto out;
   174	
   175	out_free_fdt:
   176		kvfree(fdt);
   177	out:
   178		kfree(rmem);
   179		kfree(modified_cmdline);
   180		kexec_free_elf_info(&elf_info);
   181	
   182		return ret ? ERR_PTR(ret) : NULL;
   183	}
   184	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Sourabh Jain]

On 26/12/25 19:36, Coiby Xu wrote:
> Based on the CONFIG_CRASH_DM_CRYPT feature, this patch adds
> LUKS-encrypted device dump target support to PowerPC 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.
>
> 1st kernel will build up the kernel command parameter dmcryptkeys 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/
>
> Cc: Thomas Staudt <tstaudt@de.ibm.com>
> 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>
> Signed-off-by: Coiby Xu <coxu@redhat.com>
> ---
>   arch/powerpc/include/asm/kexec.h |  3 ++-
>   arch/powerpc/kexec/elf_64.c      | 26 +++++++++++++++++++++++++-
>   arch/powerpc/kexec/file_load.c   | 19 +++++++++++--------
>   3 files changed, 38 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index bd4a6c42a5f3..f3d098d543b4 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -80,7 +80,8 @@ struct kimage_arch {
>   };
>   
>   char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
> -			  unsigned long cmdline_len);
> +			  unsigned long cmdline_len,
> +			  char *name, unsigned long addr);
>   int setup_purgatory(struct kimage *image, const void *slave_code,
>   		    const void *fdt, unsigned long kernel_load_addr,
>   		    unsigned long fdt_load_addr);
> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> index 5d6d616404cf..57cb3361d91b 100644
> --- a/arch/powerpc/kexec/elf_64.c
> +++ b/arch/powerpc/kexec/elf_64.c
> @@ -81,13 +81,37 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   
>   		/* Setup cmdline for kdump kernel case */
>   		modified_cmdline = setup_kdump_cmdline(image, cmdline,
> -						       cmdline_len);
> +						       cmdline_len,
> +						       "elfcorehdr",
> +						       image->elf_load_addr);
>   		if (!modified_cmdline) {
>   			pr_err("Setting up cmdline for kdump kernel failed\n");
>   			ret = -EINVAL;
>   			goto out;
>   		}
>   		cmdline = modified_cmdline;
> +		cmdline_len = strlen(cmdline) + 1;
> +
> +		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");
> +			return ERR_PTR(ret);
> +		}
> +
> +		if (image->dm_crypt_keys_addr != 0) {
> +			modified_cmdline = setup_kdump_cmdline(image, cmdline,
> +							       cmdline_len,
> +							       "dmcryptkeys",
> +							       image->dm_crypt_keys_addr);
> +			if (!modified_cmdline) {
> +				pr_err("Setting up cmdline for kdump kernel failed\n");
> +				ret = -EINVAL;
> +				goto out;
> +			}
> +			cmdline = modified_cmdline;
> +		}
>   	}
>   
>   	if (initrd != NULL) {
> diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
> index 4284f76cbef5..e1c08050286d 100644
> --- a/arch/powerpc/kexec/file_load.c
> +++ b/arch/powerpc/kexec/file_load.c
> @@ -23,38 +23,41 @@
>   #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
>   
>   /**
> - * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
> + * setup_kdump_cmdline - Prepend "<name>=<addr> " to command line
>    *                       of kdump kernel for exporting the core.
>    * @image:               Kexec image
>    * @cmdline:             Command line parameters to update.
>    * @cmdline_len:         Length of the cmdline parameters.
> + * @name:                Name e.g elfcorehdr.
> + * @addr:                Memory address.
>    *
>    * kdump segment must be setup before calling this function.
>    *
>    * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
>    */
>   char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
> -			  unsigned long cmdline_len)
> +			  unsigned long cmdline_len,
> +			  char *name, unsigned long addr)
>   {
> -	int elfcorehdr_strlen;
> +	unsigned long parameter_len;
>   	char *cmdline_ptr;
>   
>   	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
>   	if (!cmdline_ptr)
>   		return NULL;
>   
> -	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
> -				    image->elf_load_addr);
> +	parameter_len = sprintf(cmdline_ptr, "%s=0x%lx ", name, addr);
>   
> -	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
> -		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
> +	if (parameter_len + cmdline_len > COMMAND_LINE_SIZE) {
> +		pr_err("Appending %s=<addr> exceeds cmdline size\n", name);
>   		kfree(cmdline_ptr);
>   		return NULL;
>   	}
>   
> -	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
> +	memcpy(cmdline_ptr + parameter_len, cmdline, cmdline_len);
>   	// Ensure it's nul terminated
>   	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
> +	kfree(cmdline);

When setup_kdump_cmdline() is called for elfcorehdr, cmdline holds the
same pointer as image->cmdline_buf. Freeing it here may therefore
cause issues, right?

Currently, image->cmdline_buf is not used after calling the
architecture-specific load function (elf64_load on powerpc).
However, kimage_file_post_load_cleanup() later calls kfree() on
the same address.

>   	return cmdline_ptr;
>   }
>   
>
> base-commit: ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1

Re: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Coiby Xu]

On Thu, Jan 01, 2026 at 08:36:09PM +0530, Sourabh Jain wrote:
>
>
>On 26/12/25 19:36, Coiby Xu wrote:
>>Based on the CONFIG_CRASH_DM_CRYPT feature, this patch adds
>>LUKS-encrypted device dump target support to PowerPC 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.
>>
>>1st kernel will build up the kernel command parameter dmcryptkeys 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/
>>
>>Cc: Thomas Staudt <tstaudt@de.ibm.com>
>>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>
>>Signed-off-by: Coiby Xu <coxu@redhat.com>
>>---
>>  arch/powerpc/include/asm/kexec.h |  3 ++-
>>  arch/powerpc/kexec/elf_64.c      | 26 +++++++++++++++++++++++++-
>>  arch/powerpc/kexec/file_load.c   | 19 +++++++++++--------
>>  3 files changed, 38 insertions(+), 10 deletions(-)
>>
>>diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
>>index bd4a6c42a5f3..f3d098d543b4 100644
>>--- a/arch/powerpc/include/asm/kexec.h
>>+++ b/arch/powerpc/include/asm/kexec.h
>>@@ -80,7 +80,8 @@ struct kimage_arch {
>>  };
>>  char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
>>-			  unsigned long cmdline_len);
>>+			  unsigned long cmdline_len,
>>+			  char *name, unsigned long addr);
>>  int setup_purgatory(struct kimage *image, const void *slave_code,
>>  		    const void *fdt, unsigned long kernel_load_addr,
>>  		    unsigned long fdt_load_addr);
>>diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
>>index 5d6d616404cf..57cb3361d91b 100644
>>--- a/arch/powerpc/kexec/elf_64.c
>>+++ b/arch/powerpc/kexec/elf_64.c
>>@@ -81,13 +81,37 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>>  		/* Setup cmdline for kdump kernel case */
>>  		modified_cmdline = setup_kdump_cmdline(image, cmdline,
>>-						       cmdline_len);
>>+						       cmdline_len,
>>+						       "elfcorehdr",
>>+						       image->elf_load_addr);
>>  		if (!modified_cmdline) {
>>  			pr_err("Setting up cmdline for kdump kernel failed\n");
>>  			ret = -EINVAL;
>>  			goto out;
>>  		}
>>  		cmdline = modified_cmdline;
>>+		cmdline_len = strlen(cmdline) + 1;
>>+
>>+		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");
>>+			return ERR_PTR(ret);
>>+		}
>>+
>>+		if (image->dm_crypt_keys_addr != 0) {
>>+			modified_cmdline = setup_kdump_cmdline(image, cmdline,
>>+							       cmdline_len,
>>+							       "dmcryptkeys",
>>+							       image->dm_crypt_keys_addr);
>>+			if (!modified_cmdline) {
>>+				pr_err("Setting up cmdline for kdump kernel failed\n");
>>+				ret = -EINVAL;
>>+				goto out;
>>+			}
>>+			cmdline = modified_cmdline;
>>+		}
>>  	}
>>  	if (initrd != NULL) {
>>diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
>>index 4284f76cbef5..e1c08050286d 100644
>>--- a/arch/powerpc/kexec/file_load.c
>>+++ b/arch/powerpc/kexec/file_load.c
>>@@ -23,38 +23,41 @@
>>  #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
>>  /**
>>- * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
>>+ * setup_kdump_cmdline - Prepend "<name>=<addr> " to command line
>>   *                       of kdump kernel for exporting the core.
>>   * @image:               Kexec image
>>   * @cmdline:             Command line parameters to update.
>>   * @cmdline_len:         Length of the cmdline parameters.
>>+ * @name:                Name e.g elfcorehdr.
>>+ * @addr:                Memory address.
>>   *
>>   * kdump segment must be setup before calling this function.
>>   *
>>   * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
>>   */
>>  char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
>>-			  unsigned long cmdline_len)
>>+			  unsigned long cmdline_len,
>>+			  char *name, unsigned long addr)
>>  {
>>-	int elfcorehdr_strlen;
>>+	unsigned long parameter_len;
>>  	char *cmdline_ptr;
>>  	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
>>  	if (!cmdline_ptr)
>>  		return NULL;
>>-	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
>>-				    image->elf_load_addr);
>>+	parameter_len = sprintf(cmdline_ptr, "%s=0x%lx ", name, addr);
>>-	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
>>-		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
>>+	if (parameter_len + cmdline_len > COMMAND_LINE_SIZE) {
>>+		pr_err("Appending %s=<addr> exceeds cmdline size\n", name);
>>  		kfree(cmdline_ptr);
>>  		return NULL;
>>  	}
>>-	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
>>+	memcpy(cmdline_ptr + parameter_len, cmdline, cmdline_len);
>>  	// Ensure it's nul terminated
>>  	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
>>+	kfree(cmdline);
>
>When setup_kdump_cmdline() is called for elfcorehdr, cmdline holds the
>same pointer as image->cmdline_buf. Freeing it here may therefore
>cause issues, right?

Yes, you are right, I'll drop the above kfree in next version.

>
>Currently, image->cmdline_buf is not used after calling the
>architecture-specific load function (elf64_load on powerpc).
>However, kimage_file_post_load_cleanup() later calls kfree() on
>the same address.

I missed kimage_file_post_load_cleanup. Thanks for pointing it out!


-- 
Best regards,
Coiby

[PATCH v2] powerpc/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 PowerPC, we only need to let 1st kernel
build up the kernel command parameter dmcryptkeys as similar to
elfcorehdr to pass the memory address of the stored info of dm-crypt
keys to the kdump kernel.

Note to avoid a building failure [2] caused by undeclared function
crash_load_dm_crypt_keys when CONFIG_CRASH_DUMP is not enabled,
realign the function declaration with CONFIG_CRASH_DM_CRYPT.

[1] https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/
[2] https://lore.kernel.org/oe-kbuild-all/202512272218.ghBaSjzO-lkp@intel.com/

Cc: Thomas Staudt <tstaudt@de.ibm.com>
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: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
v2:
- fix double kfree issue [Sourabh]
- corretly kfree old modified_cmdline
- use imperative mood for commit message
- fix a compiling error caught by kernel test robot

 arch/powerpc/include/asm/kexec.h |  3 ++-
 arch/powerpc/kexec/elf_64.c      | 27 ++++++++++++++++++++++++++-
 arch/powerpc/kexec/file_load.c   | 18 ++++++++++--------
 include/linux/crash_core.h       | 14 +++++++-------
 4 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index bd4a6c42a5f3..f3d098d543b4 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -80,7 +80,8 @@ struct kimage_arch {
 };
 
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
-			  unsigned long cmdline_len);
+			  unsigned long cmdline_len,
+			  char *name, unsigned long addr);
 int setup_purgatory(struct kimage *image, const void *slave_code,
 		    const void *fdt, unsigned long kernel_load_addr,
 		    unsigned long fdt_load_addr);
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 5d6d616404cf..995d7e8e98e1 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -81,13 +81,38 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 
 		/* Setup cmdline for kdump kernel case */
 		modified_cmdline = setup_kdump_cmdline(image, cmdline,
-						       cmdline_len);
+						       cmdline_len,
+						       "elfcorehdr",
+						       image->elf_load_addr);
 		if (!modified_cmdline) {
 			pr_err("Setting up cmdline for kdump kernel failed\n");
 			ret = -EINVAL;
 			goto out;
 		}
 		cmdline = modified_cmdline;
+		cmdline_len = strlen(cmdline) + 1;
+
+		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");
+			return ERR_PTR(ret);
+		}
+
+		if (image->dm_crypt_keys_addr != 0) {
+			modified_cmdline = setup_kdump_cmdline(image, cmdline,
+							       cmdline_len,
+							       "dmcryptkeys",
+							       image->dm_crypt_keys_addr);
+			kfree(cmdline);
+			if (!modified_cmdline) {
+				pr_err("Setting up cmdline for kdump kernel failed\n");
+				ret = -EINVAL;
+				goto out;
+			}
+			cmdline = modified_cmdline;
+		}
 	}
 
 	if (initrd != NULL) {
diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
index 4284f76cbef5..9964c57785f5 100644
--- a/arch/powerpc/kexec/file_load.c
+++ b/arch/powerpc/kexec/file_load.c
@@ -23,36 +23,38 @@
 #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
 
 /**
- * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
+ * setup_kdump_cmdline - Prepend "<name>=<addr> " to command line
  *                       of kdump kernel for exporting the core.
  * @image:               Kexec image
  * @cmdline:             Command line parameters to update.
  * @cmdline_len:         Length of the cmdline parameters.
+ * @name:                Name e.g elfcorehdr.
+ * @addr:                Memory address.
  *
  * kdump segment must be setup before calling this function.
  *
  * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
  */
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
-			  unsigned long cmdline_len)
+			  unsigned long cmdline_len,
+			  char *name, unsigned long addr)
 {
-	int elfcorehdr_strlen;
+	unsigned long parameter_len;
 	char *cmdline_ptr;
 
 	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
 	if (!cmdline_ptr)
 		return NULL;
 
-	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
-				    image->elf_load_addr);
+	parameter_len = sprintf(cmdline_ptr, "%s=0x%lx ", name, addr);
 
-	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
-		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
+	if (parameter_len + cmdline_len > COMMAND_LINE_SIZE) {
+		pr_err("Appending %s=<addr> exceeds cmdline size\n", name);
 		kfree(cmdline_ptr);
 		return NULL;
 	}
 
-	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
+	memcpy(cmdline_ptr + parameter_len, cmdline, cmdline_len);
 	// Ensure it's nul terminated
 	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
 	return cmdline_ptr;
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d35726d6a415..e128270c703f 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 */

base-commit: 7f98ab9da046865d57c102fd3ca9669a29845f67
-- 
2.52.0

Re: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Coiby Xu]

On Sat, Dec 27, 2025 at 10:35:11PM +0800, kernel test robot wrote:
>Hi Coiby,
>
>kernel test robot noticed the following build errors:
>
>[auto build test ERROR on ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1]
>
>url:    https://github.com/intel-lab-lkp/linux/commits/Coiby-Xu/powerpc-kdump-pass-dm-crypt-keys-to-kdump-kernel/20251226-220726
>base:   ccd1cdca5cd433c8a5dff78b69a79b31d9b77ee1
>patch link:    https://lore.kernel.org/r/20251226140636.1378505-1-coxu%40redhat.com
>patch subject: [PATCH] powerpc/kdump: pass dm-crypt keys to kdump kernel
>config: powerpc64-randconfig-001-20251227 (https://download.01.org/0day-ci/archive/20251227/202512272218.ghBaSjzO-lkp@intel.com/config)
>compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 4ef602d446057dabf5f61fb221669ecbeda49279)
>reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251227/202512272218.ghBaSjzO-lkp@intel.com/reproduce)
>
>If you fix the issue in a separate patch/commit (i.e. not just a new version of
>the same patch/commit), kindly add following tags
>| Reported-by: kernel test robot <lkp@intel.com>
>| Closes: https://lore.kernel.org/oe-kbuild-all/202512272218.ghBaSjzO-lkp@intel.com/
>
>All errors (new ones prefixed by >>):
>
>>> arch/powerpc/kexec/elf_64.c:95:9: error: call to undeclared function 'crash_load_dm_crypt_keys'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
>      95 |                 ret = crash_load_dm_crypt_keys(image);
>         |                       ^
>   1 error generated.

This issue has been addressed in v2
https://lore.kernel.org/all/20260106074039.564707-1-coxu@redhat.com/

Thanks!

-- 
Best regards,
Coiby

Re: [PATCH v2] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Sourabh Jain]

On 06/01/26 13:10, Coiby Xu 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 PowerPC, we only need to let 1st kernel
> build up the kernel command parameter dmcryptkeys as similar to
> elfcorehdr to pass the memory address of the stored info of dm-crypt
> keys to the kdump kernel.
>
> Note to avoid a building failure [2] caused by undeclared function
> crash_load_dm_crypt_keys when CONFIG_CRASH_DUMP is not enabled,
> realign the function declaration with CONFIG_CRASH_DM_CRYPT.
>
> [1] https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/
> [2] https://lore.kernel.org/oe-kbuild-all/202512272218.ghBaSjzO-lkp@intel.com/
>
> Cc: Thomas Staudt <tstaudt@de.ibm.com>
> 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: Sourabh Jain <sourabhjain@linux.ibm.com>
> Signed-off-by: Coiby Xu <coxu@redhat.com>
> ---
> v2:
> - fix double kfree issue [Sourabh]
> - corretly kfree old modified_cmdline
> - use imperative mood for commit message
> - fix a compiling error caught by kernel test robot
>
>   arch/powerpc/include/asm/kexec.h |  3 ++-
>   arch/powerpc/kexec/elf_64.c      | 27 ++++++++++++++++++++++++++-
>   arch/powerpc/kexec/file_load.c   | 18 ++++++++++--------
>   include/linux/crash_core.h       | 14 +++++++-------
>   4 files changed, 45 insertions(+), 17 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index bd4a6c42a5f3..f3d098d543b4 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -80,7 +80,8 @@ struct kimage_arch {
>   };
>   
>   char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
> -			  unsigned long cmdline_len);
> +			  unsigned long cmdline_len,
> +			  char *name, unsigned long addr);
>   int setup_purgatory(struct kimage *image, const void *slave_code,
>   		    const void *fdt, unsigned long kernel_load_addr,
>   		    unsigned long fdt_load_addr);
> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> index 5d6d616404cf..995d7e8e98e1 100644
> --- a/arch/powerpc/kexec/elf_64.c
> +++ b/arch/powerpc/kexec/elf_64.c
> @@ -81,13 +81,38 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   
>   		/* Setup cmdline for kdump kernel case */
>   		modified_cmdline = setup_kdump_cmdline(image, cmdline,
> -						       cmdline_len);
> +						       cmdline_len,
> +						       "elfcorehdr",
> +						       image->elf_load_addr);
>   		if (!modified_cmdline) {
>   			pr_err("Setting up cmdline for kdump kernel failed\n");
>   			ret = -EINVAL;
>   			goto out;
>   		}
>   		cmdline = modified_cmdline;
> +		cmdline_len = strlen(cmdline) + 1;

I have a limited understanding of the new dm-crypt keys, but the way they
are loaded and the additional command-line options added for the kdump
kernel look good to me.

Feel free to add:
Acked-by: Sourabh Jain <sourabhjain@linux.ibm.com>


> +
> +		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");
> +			return ERR_PTR(ret);
> +		}
> +
> +		if (image->dm_crypt_keys_addr != 0) {
> +			modified_cmdline = setup_kdump_cmdline(image, cmdline,
> +							       cmdline_len,
> +							       "dmcryptkeys",
> +							       image->dm_crypt_keys_addr);
> +			kfree(cmdline);
> +			if (!modified_cmdline) {
> +				pr_err("Setting up cmdline for kdump kernel failed\n");
> +				ret = -EINVAL;
> +				goto out;
> +			}
> +			cmdline = modified_cmdline;
> +		}
>   	}
>   
>   	if (initrd != NULL) {
> diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
> index 4284f76cbef5..9964c57785f5 100644
> --- a/arch/powerpc/kexec/file_load.c
> +++ b/arch/powerpc/kexec/file_load.c
> @@ -23,36 +23,38 @@
>   #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
>   
>   /**
> - * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
> + * setup_kdump_cmdline - Prepend "<name>=<addr> " to command line
>    *                       of kdump kernel for exporting the core.
>    * @image:               Kexec image
>    * @cmdline:             Command line parameters to update.
>    * @cmdline_len:         Length of the cmdline parameters.
> + * @name:                Name e.g elfcorehdr.
> + * @addr:                Memory address.
>    *
>    * kdump segment must be setup before calling this function.
>    *
>    * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
>    */
>   char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
> -			  unsigned long cmdline_len)
> +			  unsigned long cmdline_len,
> +			  char *name, unsigned long addr)
>   {
> -	int elfcorehdr_strlen;
> +	unsigned long parameter_len;
>   	char *cmdline_ptr;
>   
>   	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
>   	if (!cmdline_ptr)
>   		return NULL;
>   
> -	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
> -				    image->elf_load_addr);
> +	parameter_len = sprintf(cmdline_ptr, "%s=0x%lx ", name, addr);
>   
> -	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
> -		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
> +	if (parameter_len + cmdline_len > COMMAND_LINE_SIZE) {
> +		pr_err("Appending %s=<addr> exceeds cmdline size\n", name);
>   		kfree(cmdline_ptr);
>   		return NULL;
>   	}
>   
> -	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
> +	memcpy(cmdline_ptr + parameter_len, cmdline, cmdline_len);
>   	// Ensure it's nul terminated
>   	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
>   	return cmdline_ptr;
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index d35726d6a415..e128270c703f 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 */
>
> base-commit: 7f98ab9da046865d57c102fd3ca9669a29845f67

Re: [PATCH v2] powerpc/kdump: pass dm-crypt keys to kdump kernel

[Coiby Xu]

On Wed, Jan 07, 2026 at 02:32:41PM +0530, Sourabh Jain wrote:
>
>
>On 06/01/26 13:10, Coiby Xu 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 PowerPC, we only need to let 1st kernel
>>build up the kernel command parameter dmcryptkeys as similar to
>>elfcorehdr to pass the memory address of the stored info of dm-crypt
>>keys to the kdump kernel.
>>
>>Note to avoid a building failure [2] caused by undeclared function
>>crash_load_dm_crypt_keys when CONFIG_CRASH_DUMP is not enabled,
>>realign the function declaration with CONFIG_CRASH_DM_CRYPT.
>>
>>[1] https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/
>>[2] https://lore.kernel.org/oe-kbuild-all/202512272218.ghBaSjzO-lkp@intel.com/
>>
>>Cc: Thomas Staudt <tstaudt@de.ibm.com>
>>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: Sourabh Jain <sourabhjain@linux.ibm.com>
>>Signed-off-by: Coiby Xu <coxu@redhat.com>
>>---
>>v2:
>>- fix double kfree issue [Sourabh]
>>- corretly kfree old modified_cmdline
>>- use imperative mood for commit message
>>- fix a compiling error caught by kernel test robot
>>
>>  arch/powerpc/include/asm/kexec.h |  3 ++-
>>  arch/powerpc/kexec/elf_64.c      | 27 ++++++++++++++++++++++++++-
>>  arch/powerpc/kexec/file_load.c   | 18 ++++++++++--------
>>  include/linux/crash_core.h       | 14 +++++++-------
>>  4 files changed, 45 insertions(+), 17 deletions(-)
>>
>>diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
>>index bd4a6c42a5f3..f3d098d543b4 100644
>>--- a/arch/powerpc/include/asm/kexec.h
>>+++ b/arch/powerpc/include/asm/kexec.h
>>@@ -80,7 +80,8 @@ struct kimage_arch {
>>  };
>>  char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
>>-			  unsigned long cmdline_len);
>>+			  unsigned long cmdline_len,
>>+			  char *name, unsigned long addr);
>>  int setup_purgatory(struct kimage *image, const void *slave_code,
>>  		    const void *fdt, unsigned long kernel_load_addr,
>>  		    unsigned long fdt_load_addr);
>>diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
>>index 5d6d616404cf..995d7e8e98e1 100644
>>--- a/arch/powerpc/kexec/elf_64.c
>>+++ b/arch/powerpc/kexec/elf_64.c
>>@@ -81,13 +81,38 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>>  		/* Setup cmdline for kdump kernel case */
>>  		modified_cmdline = setup_kdump_cmdline(image, cmdline,
>>-						       cmdline_len);
>>+						       cmdline_len,
>>+						       "elfcorehdr",
>>+						       image->elf_load_addr);
>>  		if (!modified_cmdline) {
>>  			pr_err("Setting up cmdline for kdump kernel failed\n");
>>  			ret = -EINVAL;
>>  			goto out;
>>  		}
>>  		cmdline = modified_cmdline;
>>+		cmdline_len = strlen(cmdline) + 1;
>
>I have a limited understanding of the new dm-crypt keys, but the way they
>are loaded and the additional command-line options added for the kdump
>kernel look good to me.
>
>Feel free to add:
>Acked-by: Sourabh Jain <sourabhjain@linux.ibm.com>

Thanks for reviewing and acknowledging the patch!

-- 
Best regards,
Coiby