Re: [PATCH v2] kexec: Select ima_get/free_kexec_buffer() with CONFIG_HAVE_IMA_KEXEC(_OF)

[Jonathan McDowell <noodles@earth.li>]

On Tue, Oct 20, 2026 at 10:37:27AM +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> On x86, if CONFIG_OF_FLATTREE is enabled, the kernel uses the device tree
> implementation of ima_get/free_kexec_buffer(). However, x86 passes the IMA
> buffer location through setup_data, not through the device tree, so the
> buffer is never found and the IMA measurement list is not carried over
> across kexec.
> 
> Introduce CONFIG_HAVE_IMA_KEXEC_OF (which selects CONFIG_HAVE_IMA_KEXEC)
> and select it for the architectures that pass the IMA buffer location
> through the device tree, via of_kexec_alloc_and_setup_fdt() (arm64,
> powerpc and riscv). Build the device tree implementation of
> ima_get/free_kexec_buffer() only if the new option is enabled.
> 
> Select the new option also on LoongArch, to preserve the current behavior
> and avoid a link failure. LoongArch does not pass the buffer location to
> the next kernel yet; this will be addressed separately.
> 
> Finally, don't select it for x86, and use x86's own setup_data-based
> implementation regardless of CONFIG_OF_FLATTREE.
> 
> Fixes: b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on kexec")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

Reviewed-By: Jonathan McDowell <noodles@meta.com>

I think my original intent when adding the ACPI x86 passthrough was to 
ensure I didn't break anything for anyone who'd been trying to use OF 
with x86 and pass it through, but if it wasn't even wired up there then 
that's not a concern.

> ---
> 
> v2:
> - Reworded the commit message (no code changes), suggested by Mimi
> 
>  arch/arm64/Kconfig      | 2 +-
>  arch/loongarch/Kconfig  | 2 +-
>  arch/powerpc/Kconfig    | 2 +-
>  arch/riscv/Kconfig      | 2 +-
>  arch/x86/kernel/setup.c | 2 +-
>  drivers/of/kexec.c      | 4 ++--
>  kernel/Kconfig.kexec    | 4 ++++
>  7 files changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b5a51b0ef944..4b7e248b6c91 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1697,7 +1697,7 @@ config ARCH_SUPPORTS_KEXEC_FILE
>  config ARCH_SELECTS_KEXEC_FILE
>  	def_bool y
>  	depends on KEXEC_FILE
> -	select HAVE_IMA_KEXEC if IMA
> +	select HAVE_IMA_KEXEC_OF if IMA
>  
>  config ARCH_SUPPORTS_KEXEC_SIG
>  	def_bool y
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 2067d1f2ad7a..b5420d482da4 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -690,7 +690,7 @@ config ARCH_SELECTS_KEXEC_FILE
>  	depends on KEXEC_FILE
>  	select KEXEC_ELF
>  	select RELOCATABLE
> -	select HAVE_IMA_KEXEC if IMA
> +	select HAVE_IMA_KEXEC_OF if IMA
>  
>  config ARCH_SUPPORTS_CRASH_DUMP
>  	def_bool 64BIT
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 2580e27e4328..096c6061893b 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -643,7 +643,7 @@ config ARCH_SELECTS_KEXEC_FILE
>  	def_bool y
>  	depends on KEXEC_FILE
>  	select KEXEC_ELF
> -	select HAVE_IMA_KEXEC if IMA
> +	select HAVE_IMA_KEXEC_OF if IMA
>  
>  config PPC64_BIG_ENDIAN_ELF_ABI_V2
>  	# Option is available to BFD, but LLD does not support ELFv1 so this is
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index f8e26c4bed2b..161bf8a65beb 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -1118,7 +1118,7 @@ config ARCH_SUPPORTS_KEXEC_FILE
>  config ARCH_SELECTS_KEXEC_FILE
>  	def_bool y
>  	depends on KEXEC_FILE
> -	select HAVE_IMA_KEXEC if IMA
> +	select HAVE_IMA_KEXEC_OF if IMA
>  	select KEXEC_ELF
>  
>  config ARCH_SUPPORTS_KEXEC_PURGATORY
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index cda6adb9f69c..bc17e353c099 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -421,7 +421,7 @@ static void __init add_early_ima_buffer(u64 phys_addr)
>  #endif
>  }
>  
> -#if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE)
> +#ifdef CONFIG_HAVE_IMA_KEXEC
>  int __init ima_free_kexec_buffer(void)
>  {
>  	if (!ima_kexec_buffer_size)
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 029903b986cb..724f29fef0c0 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -116,7 +116,7 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
>  	return 0;
>  }
>  
> -#ifdef CONFIG_HAVE_IMA_KEXEC
> +#ifdef CONFIG_HAVE_IMA_KEXEC_OF
>  /**
>   * ima_get_kexec_buffer - get IMA buffer from the previous kernel
>   * @addr:	On successful return, set to point to the buffer contents.
> @@ -196,7 +196,7 @@ static void remove_ima_buffer(void *fdt, int chosen_node)
>  	size_t size;
>  	const void *prop;
>  
> -	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> +	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC_OF))
>  		return;
>  
>  	prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> index 15632358bcf7..c6ed60f04ea4 100644
> --- a/kernel/Kconfig.kexec
> +++ b/kernel/Kconfig.kexec
> @@ -17,6 +17,10 @@ config KEXEC_ELF
>  config HAVE_IMA_KEXEC
>  	bool
>  
> +config HAVE_IMA_KEXEC_OF
> +	bool
> +	select HAVE_IMA_KEXEC
> +
>  config KEXEC
>  	bool "Enable kexec system call"
>  	depends on ARCH_SUPPORTS_KEXEC
> -- 
> 2.43.0

J.

-- 
... "You are in a twisty little maze of lookup tables, all different." --
    Joe Zeff, The Scary Devil Monastery