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

From: Johannes Schindelin
Subject: Re: [Qemu-devel] /* XXX: suppress this hack */
Date: Tue, 12 Oct 2004 18:25:11 +0200 (CEST)


On Mon, 11 Oct 2004, Johannes Schindelin wrote:

> Hi,
> 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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