linux-hardening - [PATCH v5 22/27] x86/build: set type_of

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Date:   Tue, 14 Mar 2023 13:13:49 +0300
From:   Evgeniy Baskov <baskov@...ras.ru>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Evgeniy Baskov <baskov@...ras.ru>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Peter Jones <pjones@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        "Limonciello, Mario" <mario.limonciello@....com>,
        joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
        x86@...nel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v5 22/27] x86/build: set type_of_loader for EFISTUB

After switching to the local copy of boot_params, EFISTUB stopped
setting type_of_loader, using the default value of 0. Restore that
behavior by assigning the right value at the build time.

Signed-off-by: Evgeniy Baskov <baskov@...ras.ru>
---
 arch/x86/boot/tools/build.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 476ef05f16fb..5ac4f08ed923 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -588,6 +588,8 @@ int main(int argc, char **argv)
 	memcpy(output + setup_size + efi_boot_params + SETUP_HEADER_OFFSET,
 	       setup_header, 0x290 - SETUP_HEADER_OFFSET
 	       /* == max possible sizeof(struct setup_header) */);
+	/* Set type_of_loader to the one that EFISTUB uses for the local copy */
+	output[setup_size + efi_boot_params + SETUP_HEADER_OFFSET + 0x1F] = 0x21;
 #endif
 
 	/* Calculate and write kernel checksum. */
-- 
2.39.2