Re: [PATCH 1/2] kexec: fix KEXEC_FILE dependencies

[Conor Dooley <conor@kernel.org>]

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On Mon, Oct 23, 2023 at 01:01:54PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The cleanup for the CONFIG_KEXEC Kconfig logic accidentally changed the
> 'depends on CRYPTO=y' dependency to a plain 'depends on CRYPTO', which
> causes a link failure when all the crypto support is in a loadable module
> and kexec_file support is built-in:
> 
> x86_64-linux-ld: vmlinux.o: in function `__x64_sys_kexec_file_load':
> (.text+0x32e30a): undefined reference to `crypto_alloc_shash'
> x86_64-linux-ld: (.text+0x32e58e): undefined reference to `crypto_shash_update'
> x86_64-linux-ld: (.text+0x32e6ee): undefined reference to `crypto_shash_final'
> 
> Both s390 and x86 have this problem, while ppc64 and riscv have the
> correct dependency already. On riscv, the dependency is only used
> for the purgatory, not for the kexec_file code itself, which may
> be a bit surprising as it means that with CONFIG_CRYPTO=m, it is
> possible to enable KEXEC_FILE but then the purgatory code is silently
> left out.
> 
> Move this into the common Kconfig.kexec file in a way that is
> correct everywhere, using the dependency on CRYPTO_SHA256=y only
> when the purgatory code is available. This requires reversing the
> dependency between ARCH_SUPPORTS_KEXEC_PURGATORY and KEXEC_FILE,
> but the effect remains the same, other than making riscv behave
> like the other ones.
> 
> On s390, there is an additional dependency on CRYPTO_SHA256_S390, which
> should technically not be required but gives better performance. Remove
> this dependency here, noting that it was not present in the initial
> Kconfig code but was brought in without an explanation in commit
> 71406883fd357 ("s390/kexec_file: Add kexec_file_load system call").
> 
> Fixes: 6af5138083005 ("x86/kexec: refactor for kernel/Kconfig.kexec")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/powerpc/Kconfig | 4 ++--

>  arch/riscv/Kconfig   | 4 +---

This doesn't appear to work for rv32. The defconfig build in our
patchwork automation complains:
  /tmp/tmp.Aq21JVRQTx/arch/riscv/purgatory/entry.S:29:2: error: instruction requires the following: RV64I Base Instruction Set

>  arch/s390/Kconfig    | 4 ++--
>  arch/x86/Kconfig     | 4 ++--
>  kernel/Kconfig.kexec | 1 +
>  5 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index d5d5388973ac7..4640cee33f123 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -607,10 +607,10 @@ config ARCH_SUPPORTS_KEXEC
>  	def_bool PPC_BOOK3S || PPC_E500 || (44x && !SMP)
>  
>  config ARCH_SUPPORTS_KEXEC_FILE
> -	def_bool PPC64 && CRYPTO=y && CRYPTO_SHA256=y
> +	def_bool PPC64
>  
>  config ARCH_SUPPORTS_KEXEC_PURGATORY
> -	def_bool KEXEC_FILE
> +	def_bool y
>  
>  config ARCH_SELECTS_KEXEC_FILE
>  	def_bool y
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 25474f8c12b79..f571bad2d22d0 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -687,9 +687,7 @@ config ARCH_SELECTS_KEXEC_FILE
>  	select KEXEC_ELF
>  
>  config ARCH_SUPPORTS_KEXEC_PURGATORY
> -	def_bool KEXEC_FILE
> -	depends on CRYPTO=y
> -	depends on CRYPTO_SHA256=y
> +	def_bool y

This being the problem, KEXEC_FILE is 64-bit only.

IIRC I commented on this same thing during the original conversion
patches.

Cheers,
Conor.

>  
>  config ARCH_SUPPORTS_CRASH_DUMP
>  	def_bool y
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index b0d67ac8695f9..ec77106af4137 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -253,13 +253,13 @@ config ARCH_SUPPORTS_KEXEC
>  	def_bool y
>  
>  config ARCH_SUPPORTS_KEXEC_FILE
> -	def_bool CRYPTO && CRYPTO_SHA256 && CRYPTO_SHA256_S390
> +	def_bool y
>  
>  config ARCH_SUPPORTS_KEXEC_SIG
>  	def_bool MODULE_SIG_FORMAT
>  
>  config ARCH_SUPPORTS_KEXEC_PURGATORY
> -	def_bool KEXEC_FILE
> +	def_bool y
>  
>  config ARCH_SUPPORTS_CRASH_DUMP
>  	def_bool y
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 94efde80ebf35..f9975b15ccd57 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2073,7 +2073,7 @@ config ARCH_SUPPORTS_KEXEC
>  	def_bool y
>  
>  config ARCH_SUPPORTS_KEXEC_FILE
> -	def_bool X86_64 && CRYPTO && CRYPTO_SHA256
> +	def_bool X86_64
>  
>  config ARCH_SELECTS_KEXEC_FILE
>  	def_bool y
> @@ -2081,7 +2081,7 @@ config ARCH_SELECTS_KEXEC_FILE
>  	select HAVE_IMA_KEXEC if IMA
>  
>  config ARCH_SUPPORTS_KEXEC_PURGATORY
> -	def_bool KEXEC_FILE
> +	def_bool y
>  
>  config ARCH_SUPPORTS_KEXEC_SIG
>  	def_bool y
> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> index 7aff28ded2f48..bfc636d64ff2b 100644
> --- a/kernel/Kconfig.kexec
> +++ b/kernel/Kconfig.kexec
> @@ -36,6 +36,7 @@ config KEXEC
>  config KEXEC_FILE
>  	bool "Enable kexec file based system call"
>  	depends on ARCH_SUPPORTS_KEXEC_FILE
> +	depends on CRYPTO_SHA256=y || !ARCH_SUPPORTS_KEXEC_PURGATORY
>  	select KEXEC_CORE
>  	help
>  	  This is new version of kexec system call. This system call is
> -- 
> 2.39.2
> 
> 
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