linux-kernel - [PATCH] i386, entry_32: remove page

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Message-Id: <1242861486-7255-5-git-send-email-heukelum@fastmail.fm>
Date:	Thu, 21 May 2009 01:18:02 +0200
From:	Alexander van Heukelum <heukelum@...tmail.fm>
To:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Cc:	Jan Beulich <JBeulich@...ell.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>
Subject: [PATCH] i386, entry_32: remove page_fault microoptimization

A distinct pattern exists in the handler stubs for traps. The
pagefault handler has a microoptimization where the handler
falls through to the common handler code 'error_code'. This
adds a short jump to the pagefault handler and aligns the
error_code code.

No functional change intended.

impact: prepare for introduction of zeroentry/errorentry macros

Signed-off-by: Alexander van Heukelum <heukelum@...tmail.fm>
---
 arch/x86/kernel/entry_32.S |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 0e8ac16..3c04063 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1178,8 +1178,13 @@ ENTRY(page_fault)
 	RING0_EC_FRAME
 	pushl $do_page_fault
 	CFI_ADJUST_CFA_OFFSET 4
-	ALIGN
-error_code:
+	jmp error_code
+	CFI_ENDPROC
+END(page_fault)
+
+ENTRY(error_code)
+	RING0_EC_FRAME
+	CFI_ADJUST_CFA_OFFSET 4
 	/* the function address is in %gs's slot on the stack */
 	pushl %fs
 	CFI_ADJUST_CFA_OFFSET 4
@@ -1229,7 +1234,7 @@ error_code:
 	call *%edi
 	jmp ret_from_exception
 	CFI_ENDPROC
-END(page_fault)
+END(error_code)
 
 /*
  * Debug traps and NMI can happen at the one SYSENTER instruction
-- 
1.6.0.4

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