On 02/01/2026 17:53, Breno Leitao wrote:
> Add CONFIG_KEXEC_HISTORY to store and display the kernel version from
> the previous kexec boot.
>
> When enabled, the current kernel's release string is saved to the
> "previous-release" property in the KHO device tree before kexec. On
> the next boot, if this property exists, the previous kernel version
> is retrieved and printed during early boot.
>
> This helps diagnose bugs that only manifest when kexecing from
> specific kernel versions, making it easier to correlate crashes with
> the kernel that initiated the kexec.
>
> Disabled by default to avoid overhead for users who don't need this
> information.
>
> Signed-off-by: Breno Leitao <[email protected]>
> ---
> kernel/Kconfig.kexec | 13 +++++++++++++
> kernel/liveupdate/kexec_handover.c | 29 +++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+)
>
> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> index 15632358bcf7..b770c68a3800 100644
> --- a/kernel/Kconfig.kexec
> +++ b/kernel/Kconfig.kexec
> @@ -94,6 +94,19 @@ config KEXEC_JUMP
> Jump between original kernel and kexeced kernel and invoke
> code in physical address mode via KEXEC
>
> +config KEXEC_HISTORY
> + bool "Track kexec kernel history"
> + depends on KEXEC_HANDOVER
> + help
> + When enabled, the kernel will store its release version in the
> + KHO FDT before kexec, and the newly booted kernel will read and
> + print this information during early boot.
> +
> + This is useful for debugging and auditing to know which kernel
> + version performed the kexec that booted the current kernel.
> +
> + If unsure, say N.
> +
I think we should make this default if KHO is enabled, i.e. not have a Kconfig
option for this. The cost of storing the char array is negligable.
> config CRASH_DUMP
> bool "kernel crash dumps"
> default ARCH_DEFAULT_CRASH_DUMP
> diff --git a/kernel/liveupdate/kexec_handover.c
> b/kernel/liveupdate/kexec_handover.c
> index 73da00aeaa99..06d99627bb3c 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -21,6 +21,7 @@
> #include <linux/page-isolation.h>
> #include <linux/unaligned.h>
> #include <linux/vmalloc.h>
> +#include <linux/utsname.h>
>
> #include <asm/early_ioremap.h>
>
> @@ -36,6 +37,7 @@
> #define KHO_FDT_COMPATIBLE "kho-v1"
> #define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
> #define PROP_SUB_FDT "fdt"
> +#define PROP_PREVIOUS_RELEASE "previous-release"
>
> #define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
>
> @@ -1253,6 +1255,9 @@ bool kho_finalized(void)
> struct kho_in {
> phys_addr_t fdt_phys;
> phys_addr_t scratch_phys;
> +#ifdef CONFIG_KEXEC_HISTORY
> + char previous_release[__NEW_UTS_LEN + 1];
> +#endif
> struct kho_debugfs dbg;
> };
>
> @@ -1332,6 +1337,10 @@ static __init int kho_out_fdt_setup(void)
> err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
> err |= fdt_property(root, PROP_PRESERVED_MEMORY_MAP, &empty_mem_map,
> sizeof(empty_mem_map));
> +#ifdef CONFIG_KEXEC_HISTORY
> + err |= fdt_property_string(root, PROP_PREVIOUS_RELEASE,
> + init_uts_ns.name.release);
> +#endif
> err |= fdt_end_node(root);
> err |= fdt_finish(root);
>
> @@ -1455,6 +1464,25 @@ void __init kho_memory_init(void)
> }
> }
>
> +#ifdef CONFIG_KEXEC_HISTORY
> +static void __init kho_print_previous_kernel(const void *fdt)
> +{
> + const char *prev_release;
> + int len;
> +
> + prev_release = fdt_getprop(fdt, 0, PROP_PREVIOUS_RELEASE, &len);
> + if (!prev_release || len <= 0)
> + return;
> +
> + strscpy(kho_in.previous_release, prev_release,
> + sizeof(kho_in.previous_release));
> + pr_info("This kernel was kexec'ed from kernel release: %s\n",
> + kho_in.previous_release);
Maybe s/release/version everywhere? It might not be a release, but no strong
opinion.
> +}
> +#else
> +static void __init kho_print_previous_kernel(const void *fdt) { }
> +#endif
> +
> void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
> phys_addr_t scratch_phys, u64 scratch_len)
> {
> @@ -1527,6 +1555,7 @@ void __init kho_populate(phys_addr_t fdt_phys, u64
> fdt_len,
> kho_in.scratch_phys = scratch_phys;
> kho_scratch_cnt = scratch_cnt;
> pr_info("found kexec handover data.\n");
> + kho_print_previous_kernel(fdt);
>
> out:
> if (fdt)
>
