linux-kernel - [PATCH 0/3] avoid unnecessary recompilations in x86 boot code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Tue, 20 Feb 2024 20:21:41 +0100
From: Jann Horn <jannh@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org
Cc: "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	Jann Horn <jannh@...gle.com>
Subject: [PATCH 0/3] avoid unnecessary recompilations in x86 boot code

It's been bugging me that every time I rebuild the kernel, kaslr.o and
misc.o get rebuilt just because they pull in one or two things from some
headers that change on every build. So this series moves them into a
separate file that should be faster to build.

This doesn't seem to actually make a difference in terms of wall clock
time, I think because these compiler invocations run in parallel with
kernel compression; but when I tested with an earlier version of this
patch series, I saw something like a 500ms reduction in CPU time used.

Not exactly a major win, and I guess CPU time isn't really the metric
that matters here, but still, I think this makes sense as a cleanup?

Jann Horn (3):
  x86/boot: fix KASLR hashing to use full input
  x86/boot: avoid recompiling misc.c for incremental rebuilds
  x86/boot: avoid recompiling kaslr.c for incremental rebuilds

 arch/x86/boot/compressed/Makefile       |  4 ++--
 arch/x86/boot/compressed/dynamic_vars.c | 17 +++++++++++++++
 arch/x86/boot/compressed/dynamic_vars.h | 14 ++++++++++++
 arch/x86/boot/compressed/kaslr.c        | 29 +++++++++++++++----------
 arch/x86/boot/compressed/misc.c         |  6 ++---
 5 files changed, 53 insertions(+), 17 deletions(-)
 create mode 100644 arch/x86/boot/compressed/dynamic_vars.c
 create mode 100644 arch/x86/boot/compressed/dynamic_vars.h

-- 
2.44.0.rc0.258.g7320e95886-goog