linux-kernel - Re: [GIT PULL] x86/paravirt for v2.6.33

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Date:	Wed, 9 Dec 2009 10:47:12 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/paravirt for v2.6.33



On Wed, 9 Dec 2009, Jeremy Fitzhardinge wrote:
> 
> How does this look?

I would actually prefer it if the calling convention was just made to 
match on both x86 and x86-64. Wouldn't it be nice if they both just had

> +/* kernel/ioport.c */
> +asmlinkage long sys_iopl(unsigned int, struct pt_regs *);

as the prototype, and looked the same?

I realize that right now the 32-bit PTREGSCALL() thing doesn't support 
that (very different macros for entry.S x86-32 and -64), but isn't that 
just another thing we should try to fix too?

IOW, maybe something like this would be good, and would change the x86-32 
calling convention to match the x86-64 one?

NOTE NOTE NOTE! Totally untested. Is the second argument even in %edx? I 
don't remember, I didn't check, I'm just throwing this out as a "hey, 
maybe something _like_ this can work" patch, and will be immediately 
removing it from my machine after sending this email.

		Linus

---
 arch/x86/kernel/entry_32.S |   24 ++++++++++++------------
 1 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 50b9c22..22b4431 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -725,22 +725,22 @@ END(syscall_badsys)
 /*
  * System calls that need a pt_regs pointer.
  */
-#define PTREGSCALL(name) \
+#define PTREGSCALL(name, reg) \
 	ALIGN; \
 ptregs_##name: \
-	leal 4(%esp),%eax; \
+	leal 4(%esp),reg; \
 	jmp sys_##name;
 
-PTREGSCALL(iopl)
-PTREGSCALL(fork)
-PTREGSCALL(clone)
-PTREGSCALL(vfork)
-PTREGSCALL(execve)
-PTREGSCALL(sigaltstack)
-PTREGSCALL(sigreturn)
-PTREGSCALL(rt_sigreturn)
-PTREGSCALL(vm86)
-PTREGSCALL(vm86old)
+PTREGSCALL(iopl,%edx)
+PTREGSCALL(fork,%eax)
+PTREGSCALL(clone,%eax)
+PTREGSCALL(vfork,%eax)
+PTREGSCALL(execve,%eax)
+PTREGSCALL(sigaltstack,%eax)
+PTREGSCALL(sigreturn,%eax)
+PTREGSCALL(rt_sigreturn,%eax)
+PTREGSCALL(vm86,%eax)
+PTREGSCALL(vm86old,%eax)
 
 .macro FIXUP_ESPFIX_STACK
 /*
--
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