From: Brian Gerst <bgerst@didntduck.org>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Linux-Kernel <linux-kernel@vger.kernel.org>
Subject: [PATCH] i386 head.S cleanup
Date: Fri, 24 May 2002 01:39:20 -0400 [thread overview]
Message-ID: <3CEDD208.4060706@didntduck.org> (raw)
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Cleans up some redundant code in head.S:
- Combine checking of AC and ID eflags.
- Streamline the setting of %cr0.
--
Brian Gerst
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[-- Type: text/plain, Size: 1633 bytes --]
diff -urN linux-bk/arch/i386/kernel/head.S linux/arch/i386/kernel/head.S
--- linux-bk/arch/i386/kernel/head.S Wed May 15 10:27:23 2002
+++ linux/arch/i386/kernel/head.S Fri May 24 01:22:06 2002
@@ -182,26 +182,19 @@
pushfl # push EFLAGS
popl %eax # get EFLAGS
movl %eax,%ecx # save original EFLAGS
- xorl $0x40000,%eax # flip AC bit in EFLAGS
+ xorl $0x240000,%eax # flip AC and ID bits in EFLAGS
pushl %eax # copy to EFLAGS
popfl # set EFLAGS
pushfl # get new EFLAGS
popl %eax # put it in eax
xorl %ecx,%eax # change in flags
- andl $0x40000,%eax # check if AC bit changed
+ pushl %ecx # restore original EFLAGS
+ popfl
+ testl $0x40000,%eax # check if AC bit changed
je is386
movb $4,X86 # at least 486
- movl %ecx,%eax
- xorl $0x200000,%eax # check ID flag
- pushl %eax
- popfl # if we are on a straight 486DX, SX, or
- pushfl # 487SX we can't change it
- popl %eax
- xorl %ecx,%eax
- pushl %ecx # restore original EFLAGS
- popfl
- andl $0x200000,%eax
+ testl $0x200000,%eax # check if ID bit changed
je is486
/* get vendor info */
@@ -227,18 +220,15 @@
movb %cl,X86_MASK
movl %edx,X86_CAPABILITY
-is486:
- movl %cr0,%eax # 486 or better
- andl $0x80000011,%eax # Save PG,PE,ET
- orl $0x50022,%eax # set AM, WP, NE and MP
+is486: movl $0x50022,%ecx # set AM, WP, NE and MP
jmp 2f
-is386: pushl %ecx # restore original EFLAGS
- popfl
- movl %cr0,%eax # 386
+is386: movl $2,%ecx # set MP
+2: movl %cr0,%eax
andl $0x80000011,%eax # Save PG,PE,ET
- orl $2,%eax # set MP
-2: movl %eax,%cr0
+ orl %ecx,%eax
+ movl %eax,%cr0
+
call check_x87
incb ready
lgdt gdt_descr
reply other threads:[~2002-05-24 5:43 UTC|newest]
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