[PATCH] x86, vm86: fix VM86 syscalls: use asmlinkage calling convention

From: Alexander van Heukelum <heukelum@fastmail.fm>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"intel-gfx" <intel-gfx@lists.freedesktop.org>,
	Hans de Bruin <jmdebruin@xmsnet.nl>, Ingo Molnar <mingo@elte.hu>
Subject: [PATCH] x86, vm86: fix VM86 syscalls: use asmlinkage calling convention
Date: Wed, 27 Mar 2013 20:31:02 +0100	[thread overview]
Message-ID: <1364412662.12858.140661209988437.506AD50B@webmail.messagingengine.com> (raw)
In-Reply-To: <5152F321.7020604@xmsnet.nl>

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Hi Al,

Hans de Bruin found a regression due to one of your changes. I asked him to test a fix and he reported back that it worked. (Thanks!) Can you see if you agree with the fix? Patch is attached due to webmail...

Greetings,
    Alexander

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[-- Attachment #2: 0001-x86-vm86-fix-VM86-syscalls-use-asmlinkage-calling-co.patch --]
[-- Type: text/x-patch; name="0001-x86-vm86-fix-VM86-syscalls-use-asmlinkage-calling-co.patch", Size: 2903 bytes --]

From 961a1b130aa79acb54f556a0accfcc643d1d3ed1 Mon Sep 17 00:00:00 2001
From: Alexander van Heukelum <heukelum@fastmail.fm>
Date: Tue, 26 Mar 2013 21:57:43 +0100
Subject: [PATCH] x86, vm86: fix VM86 syscalls: use asmlinkage calling convention

Commit 49cb25e9290 x86: 'get rid of pt_regs argument in vm86/vm86old'
got rid of the pt_regs stub for sys_vm86old and sys_vm86. The functions
were, however, not changed to use the asmlinkage calling convention.

The regression was reported and pinpointed by Hans de Bruin:
> commit 49cb25e9290 x86: 'get rid of pt_regs argument in vm86/vm86old'
> somehow breaks the colors when I play 'civilization I' under xdosemu.
> During the intro of the game something the colors get messed up. When
> the game begins the grass of the earth is red. Reverting the commit
> fixes the problem.

And he tested the patch too:
> Yep, the grass is green again.

Reported-and-tested-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
---
 arch/x86/include/asm/syscalls.h | 4 ++--
 arch/x86/kernel/vm86_32.c       | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 6cf0a9c..a245b88 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -37,8 +37,8 @@ asmlinkage int sys_get_thread_area(struct user_desc __user *);
 unsigned long sys_sigreturn(void);
 
 /* kernel/vm86_32.c */
-int sys_vm86old(struct vm86_struct __user *);
-int sys_vm86(unsigned long, unsigned long);
+asmlinkage int sys_vm86old(struct vm86_struct __user *);
+asmlinkage int sys_vm86(unsigned long, unsigned long);
 
 #else /* CONFIG_X86_32 */
 
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index 1cf5766..7f72807 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -202,7 +202,7 @@ out:
 static int do_vm86_irq_handling(int subfunction, int irqnumber);
 static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);
 
-int sys_vm86old(struct vm86_struct __user *v86)
+asmlinkage int sys_vm86old(struct vm86_struct __user *v86)
 {
 	struct kernel_vm86_struct info; /* declare this _on top_,
 					 * this avoids wasting of stack space.
@@ -227,11 +227,12 @@ int sys_vm86old(struct vm86_struct __user *v86)
 	do_sys_vm86(&info, tsk);
 	ret = 0;	/* we never return here */
 out:
+	asmlinkage_protect(1, ret, v86);
 	return ret;
 }
 
 
-int sys_vm86(unsigned long cmd, unsigned long arg)
+asmlinkage int sys_vm86(unsigned long cmd, unsigned long arg)
 {
 	struct kernel_vm86_struct info; /* declare this _on top_,
 					 * this avoids wasting of stack space.
@@ -278,6 +279,7 @@ int sys_vm86(unsigned long cmd, unsigned long arg)
 	do_sys_vm86(&info, tsk);
 	ret = 0;	/* we never return here */
 out:
+	asmlinkage_protect(2, ret, cmd, arg);
 	return ret;
 }
 
-- 
1.8.1.2

