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Date:   Mon, 25 Jul 2022 20:56:19 +0800
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Subject: Fwd: [PATCH 2/4] kexec: add CONFING_KEXEC_PURGATORY_SKIP_SIG
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---------- Forwarded message ---------
=E5=8F=91=E4=BB=B6=E4=BA=BA=EF=BC=9A Albert Huang <huangjie.albert@bytedanc=
e.com>
Date: 2022=E5=B9=B47=E6=9C=8825=E6=97=A5=E5=91=A8=E4=B8=80 16:40
Subject: [PATCH 2/4] kexec: add CONFING_KEXEC_PURGATORY_SKIP_SIG
To:
Cc: huangjie.albert <huangjie.albert@bytedance.com>, Thomas Gleixner
<tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
<bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>,
<x86@kernel.org>, H. Peter Anvin <hpa@zytor.com>, Eric Biederman
<ebiederm@xmission.com>, Masahiro Yamada <masahiroy@kernel.org>,
Michal Marek <michal.lkml@markovi.net>, Nick Desaulniers
<ndesaulniers@google.com>, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com>, Brijesh Singh
<brijesh.singh@amd.com>, Michael Roth <michael.roth@amd.com>, Nathan
Chancellor <nathan@kernel.org>, Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>, Ard Biesheuvel
<ardb@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Sean
Christopherson <seanjc@google.com>, Joerg Roedel <jroedel@suse.de>,
Mark Rutland <mark.rutland@arm.com>, Kees Cook
<keescook@chromium.org>, <linux-kernel@vger.kernel.org>,
<kexec@lists.infradead.org>, <linux-kbuild@vger.kernel.org>


From: "huangjie.albert" <huangjie.albert@bytedance.com>

the verify_sha256_digest may cost 300+ ms in my test environment:
bzImage: 53M initramfs:28M

We can add a macro to control whether to enable this check. If we
can confirm that the data in this will not change, we can turn off
the check and get a faster startup.

Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
---
 arch/x86/Kconfig               | 9 +++++++++
 arch/x86/purgatory/purgatory.c | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 52a7f91527fe..adbd3a2bd60f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2052,6 +2052,15 @@ config KEXEC_BZIMAGE_VERIFY_SIG
        help
          Enable bzImage signature verification support.

+config KEXEC_PURGATORY_SKIP_SIG
+       bool "skip kexec purgatory signature verification"
+       depends on ARCH_HAS_KEXEC_PURGATORY
+       help
+         this options makes the kexec purgatory do  not signature verifica=
tion
+         which would get hundreds of milliseconds saved during kexec
boot. If we can
+         confirm that the data of each segment loaded by kexec will
not change we may
+         enable this option
+
 config CRASH_DUMP
        bool "kernel crash dumps"
        depends on X86_64 || (X86_32 && HIGHMEM)
diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.=
c
index 7558139920f8..b3f15774d86d 100644
--- a/arch/x86/purgatory/purgatory.c
+++ b/arch/x86/purgatory/purgatory.c
@@ -20,6 +20,12 @@ u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE]
__section(".kexec-purgatory");

 struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX]
__section(".kexec-purgatory");

+#ifdef CONFIG_KEXEC_PURGATORY_SKIP_SIG
+static int verify_sha256_digest(void)
+{
+       return 0;
+}
+#else
 static int verify_sha256_digest(void)
 {
        struct kexec_sha_region *ptr, *end;
@@ -39,6 +45,7 @@ static int verify_sha256_digest(void)

        return 0;
 }
+#endif

 void purgatory(void)
 {
--
2.31.1