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Re: [Qemu-devel] /* XXX: suppress this hack */

From: Fabrice Bellard
Subject: Re: [Qemu-devel] /* XXX: suppress this hack */
Date: Wed, 13 Oct 2004 00:03:44 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624

I commited a patch to fix the problem. Tell me if you see regressions in the PowerPC host case. The x86 emulation on PowerPC should be faster now.


Johannes Schindelin wrote:

On Mon, 11 Oct 2004, Johannes Schindelin wrote:


On Sun, 10 Oct 2004, Magnus Damm wrote:

Yeah, registers "r3" to "r12" are "caller save", ie these registers must
be saved before a function is called. But what about "r16" to "r23",
these are currently only used when CONFIG_USER_ONLY is set - I thought
that they were supposed to be saved by the called function prior use,
"callee save". But how does that affect the softmmu code in a bad way
but the user code works? Any ideas?

*scratcheshishead* I cannot think of one way that code should work in user
mode... IMHO there is no protection to those registers when calling libc
or a syscall.

I think I know why: the only calls made from this code (CONFIG_USER_ONLY)
are syscalls. As these happen in the kernel, no registers of the normal
user space are touched except for the return register, which is intended
to be changed. Am I right?


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