linux-kernel - [tip:x86/boot] x86/boot: Comment what finalize_identity

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Message-ID: <tip-36a39ac967a548154a0fe44d71cb0063fa05010f@git.kernel.org>
Date:	Tue, 10 May 2016 01:40:28 -0700
From:	tip-bot for Borislav Petkov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, keescook@...omium.org, brgerst@...il.com,
	luto@...capital.net, tglx@...utronix.de, bp@...en8.de,
	mingo@...nel.org, dvlasenk@...hat.com,
	linux-kernel@...r.kernel.org, bp@...e.de,
	torvalds@...ux-foundation.org, peterz@...radead.org
Subject: [tip:x86/boot] x86/boot: Comment what finalize_identity_maps() does

Commit-ID:  36a39ac967a548154a0fe44d71cb0063fa05010f
Gitweb:     http://git.kernel.org/tip/36a39ac967a548154a0fe44d71cb0063fa05010f
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Sat, 7 May 2016 11:59:40 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 10 May 2016 10:12:02 +0200

x86/boot: Comment what finalize_identity_maps() does

So it is not really obvious that finalize_identity_maps() doesn't do any
finalization but it *actually* writes CR3 with the ident PGD. Comment
that at the call site.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akpm@...ux-foundation.org
Cc: bhe@...hat.com
Cc: dyoung@...hat.com
Cc: jkosina@...e.cz
Cc: linux-tip-commits@...r.kernel.org
Cc: luto@...nel.org
Cc: vgoyal@...hat.com
Cc: yinghai@...nel.org
Link: http://lkml.kernel.org/r/20160507100541.GA24613@pd.tnic
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/boot/compressed/kaslr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index f82975b..f5a138c 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -437,6 +437,8 @@ unsigned char *choose_random_location(unsigned long input,
 	choice = random_addr;
 
 	add_identity_map(choice, output_size);
+
+	/* This actually loads the identity pagetable on x86_64. */
 	finalize_identity_maps();
 out:
 	return (unsigned char *)choice;