linux-kernel - [PATCH] fix x86-32 early fixmap initialization.

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Message-ID: <m163zh5181.fsf@ebiederm.dsl.xmission.com>
Date:	Sat, 01 Dec 2007 18:34:06 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Cc:	<linux-kernel@...r.kernel.org>, pageexec@...email.hu,
	Yinghai Lu <yinghai.lu@....com>
Subject: [PATCH] fix x86-32 early fixmap initialization.


pageexec@...email.hu writes:

> hello,
>
> i've just noticed that the chunk in i386/kernel/head.S ended up in a
> weird place, namely, it's not going to be executed as it's just after
> a 'jmp 3f' and before startup_32_smp, probably not what you intended.
> on a sidenote, the whole thing can be done in a single insn, like:
>
> movl $(swapper_pg_pmd - __PAGE_OFFSET + 0x067), (swapper_pg_dir -
> __PAGE_OFFSET+ 4092)
>
> PS: your email address ebiderman@...sson.com in the commit seems to
> be wrong as well.

Yes.  YH refresh one of my old patches and apparently got my email
address wrong.

Thanks for the reminder I thought we had fixed this problem a while ago.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>

---

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 374b7ec..ac0637a 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -193,6 +193,12 @@ default_entry:
 	jb 10b
 	movl %edi,(init_pg_tables_end - __PAGE_OFFSET)
 
+	/* Do an early initialization of the fixmap area */
+	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
+	movl $(swapper_pg_pmd - __PAGE_OFFSET), %eax
+	addl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
+	movl %eax, 4092(%edx)
+
 	xorl %ebx,%ebx				/* This is the boot CPU (BSP) */
 	jmp 3f
 /*
@@ -208,12 +214,6 @@ default_entry:
 .section .init.text,"ax",@progbits
 #endif
 
-	/* Do an early initialization of the fixmap area */
-	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
-	movl $(swapper_pg_pmd - __PAGE_OFFSET), %eax
-	addl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
-	movl %eax, 4092(%edx)
-
 #ifdef CONFIG_SMP
 ENTRY(startup_32_smp)
 	cld
--
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