arm64,ppc64le/kdump: pass dm-crypt keys to kdump kernel

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
userspace.

Link: https://lkml.kernel.org/r/20260225060347.718905-4-coxu@redhat.com
Link: https://lore.kernel.org/all/20250502011246.99238-1-coxu@redhat.com/
Link: https://github.com/devicetree-org/dt-schema/pull/181
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Sourabh Jain <sourabhjain@linux.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: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Thomas Staudt <tstaudt@de.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index fba260ad87a96730ec20c0c06a5f79ffb9bf7d04..e31fabed378a59adc7f84f105b1d554c107b26f3 100644 (file)
--- 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 5d6d616404cf936a3342d1b13f96b8cc11f8817b..ea50a072debf66c5d61dff852a207b2e49ef1c98 100644 (file)
--- 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 331646d667b9bee7d60aace26019e8139ac428db..2967e4aff80708c8ebd9d4cbc0a1f5410422a66c 100644 (file)
--- 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 c4cf3552c0183887583dff6ee04a85f89c424489..fbd253f0d3c5d12556c0becefa00ee90425f996f 100644 (file)
--- 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,