linux-kernel - Re: [PATCH v4 07/11] efi/libstub: Add generic support for parsing mem

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Date: Mon, 19 Feb 2024 11:00:24 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>,
 Kevin Loughlin <kevinloughlin@...gle.com>,
 Dionna Glaze <dionnaglaze@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski
 <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>,
 Justin Stitt <justinstitt@...gle.com>, Kees Cook <keescook@...omium.org>,
 Brian Gerst <brgerst@...il.com>, linux-arch@...r.kernel.org,
 llvm@...ts.linux.dev
Subject: Re: [PATCH v4 07/11] efi/libstub: Add generic support for parsing
 mem_encrypt=

On 2/13/24 06:41, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.org>
> 
> Parse the mem_encrypt= command line parameter from the EFI stub if
> CONFIG_ARCH_HAS_MEM_ENCRYPT=y, so that it can be passed to the early
> boot code by the arch code in the stub.
> 
> This avoids the need for the core kernel to do any string parsing very
> early in the boot.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>   drivers/firmware/efi/libstub/efi-stub-helper.c | 8 ++++++++
>   drivers/firmware/efi/libstub/efistub.h         | 2 +-
>   2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
> index bfa30625f5d0..3dc2f9aaf08d 100644
> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> @@ -24,6 +24,8 @@ static bool efi_noinitrd;
>   static bool efi_nosoftreserve;
>   static bool efi_disable_pci_dma = IS_ENABLED(CONFIG_EFI_DISABLE_PCI_DMA);
>   
> +int efi_mem_encrypt;
> +
>   bool __pure __efi_soft_reserve_enabled(void)
>   {
>   	return !efi_nosoftreserve;
> @@ -75,6 +77,12 @@ efi_status_t efi_parse_options(char const *cmdline)
>   			efi_noinitrd = true;
>   		} else if (IS_ENABLED(CONFIG_X86_64) && !strcmp(param, "no5lvl")) {
>   			efi_no5lvl = true;
> +		} else if (IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT) &&
> +			   !strcmp(param, "mem_encrypt") && val) {
> +			if (parse_option_str(val, "on"))
> +				efi_mem_encrypt = 1;
> +			else if (parse_option_str(val, "off"))
> +				efi_mem_encrypt = -1;

With CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT having recently been 
removed, I'm not sure what parsing for mem_encrypt=off does.

(Same thing in the next patch.)

Thanks,
Tom

>   		} else if (!strcmp(param, "efi") && val) {
>   			efi_nochunk = parse_option_str(val, "nochunk");
>   			efi_novamap |= parse_option_str(val, "novamap");
> diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
> index 212687c30d79..a1c6ab24cd99 100644
> --- a/drivers/firmware/efi/libstub/efistub.h
> +++ b/drivers/firmware/efi/libstub/efistub.h
> @@ -37,8 +37,8 @@ extern bool efi_no5lvl;
>   extern bool efi_nochunk;
>   extern bool efi_nokaslr;
>   extern int efi_loglevel;
> +extern int efi_mem_encrypt;
>   extern bool efi_novamap;
> -
>   extern const efi_system_table_t *efi_system_table;
>   
>   typedef union efi_dxe_services_table efi_dxe_services_table_t;