linux-kernel - [PATCH 2/4] x86: syscall_get

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Message-Id: <20090923062015.D1A4214093@magilla.sf.frob.com>
Date:	Tue, 22 Sep 2009 23:20:15 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	jan.kratochvil@...hat.com, Oleg Nesterov <oleg@...hat.com>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 2/4] x86: syscall_get_nr returns int

Make syscall_get_nr() return int, so we always sign-extend
the low 32 bits of orig_ax in checks.

Signed-off-by: Roland McGrath <roland@...hat.com>
---
 arch/x86/include/asm/syscall.h |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d82f39b..8d33bc5 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -1,7 +1,7 @@
 /*
  * Access to user system call parameters and results
  *
- * Copyright (C) 2008 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
@@ -16,13 +16,13 @@
 #include <linux/sched.h>
 #include <linux/err.h>
 
-static inline long syscall_get_nr(struct task_struct *task,
-				  struct pt_regs *regs)
+/*
+ * Only the low 32 bits of orig_ax are meaningful, so we return int.
+ * This importantly ignores the high bits on 64-bit, so comparisons
+ * sign-extend the low 32 bits.
+ */
+static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 {
-	/*
-	 * We always sign-extend a -1 value being set here,
-	 * so this is always either -1L or a syscall number.
-	 */
 	return regs->orig_ax;
 }
 
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