[PATCH v4 4/7] crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging

Coiby Xu
2024-05-23T05:05:17Z

When there is CPU/memory hot-plugging, the kdump kernel image and initrd
will be reloaded. The user space can write the "reuse" command to
/sys/kernel/crash_dm_crypt_key so the stored keys can be re-saved again.

Note currently only x86 (commit ea53ad9cf73b ("x86/crash: add x86 crash
hotplug support")) and ppc (WIP) supports the new infrastructure
(commit 247262756121 ("crash: add generic infrastructure for crash
hotplug support")). If the new infrastructure get extended to all arches,
this patch can be dropped.

Signed-off-by: Coiby Xu <coxu@redhat.com>
---
kernel/crash_dump_dm_crypt.c | 30 ++++++++++++++++++++++++++----
1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
index 89fec768fba8..b4dc881cc867 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -10,12 +10,13 @@
// The key scription has the format: cryptsetup:UUID 11+36+1(NULL)=48
#define KEY_DESC_LEN 48

-static char *STATE_STR[] = {"fresh", "initialized", "recorded", "loaded"};
+static char *STATE_STR[] = {"fresh", "initialized", "recorded", "loaded", "reuse"};
static enum STATE_ENUM {
FRESH = 0,
INITIALIZED,
RECORDED,
LOADED,
+ REUSE,
} state;

static unsigned int key_count;
@@ -90,12 +91,31 @@ static int record_key_desc(const char *buf, struct dm_crypt_key *dm_key)
return 0;
}

+static void get_keys_from_kdump_reserved_memory(void)
+{
+ struct keys_header *keys_header_loaded;
+
+ arch_kexec_unprotect_crashkres();
+
+ keys_header_loaded = kmap_local_page(pfn_to_page(
+ kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT));
+
+ memcpy(keys_header, keys_header_loaded, keys_header_size);
+ kunmap_local(keys_header_loaded);
+ state = RECORDED;
+}
+
static int process_cmd(const char *buf, size_t count)
{
if (strncmp(buf, "init ", 5) == 0)
return init(buf);
else if (strncmp(buf, "record ", 7) == 0)
return record_key_desc(buf, &keys_header->keys[key_count]);
+ else if (!strcmp(buf, "reuse")) {
+ state = REUSE;
+ get_keys_from_kdump_reserved_memory();
+ return 0;
+ }

return -EINVAL;
}
@@ -175,9 +195,11 @@ int crash_load_dm_crypt_keys(struct kimage *image)
}

image->dm_crypt_keys_addr = 0;
- r = build_keys_header();
- if (r)
- return r;
+ if (state != REUSE) {
+ r = build_keys_header();
+ if (r)
+ return r;
+ }

kbuf.buffer = keys_header;
kbuf.bufsz = keys_header_size;
--
2.45.0