sysenter on x86

sysenter on x86

[Felix von Leitner]

I just added sysenter support for linux-2.5 on x86 to the diet libc, but
I noted that the original patch said user space should jump to
0xfffff000, which segfaults.  Jumping to 0xffffe000 works.

I suggest adding a comment somewhere in the kernel about the proper
calling convention, because the glibc code is frankly not readable in
this regard.

Also, I suggest adding this interface to kernel 2.4 to easy binary
compatibility.

Felix

Re: sysenter on x86

[Arjan van de Ven]

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On Sat, 2003-04-12 at 15:54, Felix von Leitner wrote:
> I just added sysenter support for linux-2.5 on x86 to the diet libc, but
> I noted that the original patch said user space should jump to
> 0xfffff000, which segfaults.  Jumping to 0xffffe000 works.
> 
> I suggest adding a comment somewhere in the kernel about the proper
> calling convention, because the glibc code is frankly not readable in
> this regard.

you HAVE to use the location as specified with the AT_SYSINFO elf flag.
The kernel is free to move this address around between builds, as long
as AT_SYSINFO gives the address for the location.

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Re: sysenter on x86

[H. Peter Anvin]

Followup to:  <1050156926.1449.2.camel@laptop.fenrus.com>
By author:    Arjan van de Ven <arjanv@redhat.com>
In newsgroup: linux.dev.kernel
>
> 
> --=-EFK+Hzuvs0Z6BUNjBVGk
> Content-Type: text/plain
> Content-Transfer-Encoding: quoted-printable
> 
> On Sat, 2003-04-12 at 15:54, Felix von Leitner wrote:
> > I just added sysenter support for linux-2.5 on x86 to the diet libc, but
> > I noted that the original patch said user space should jump to
> > 0xfffff000, which segfaults.  Jumping to 0xffffe000 works.
> >=20
> > I suggest adding a comment somewhere in the kernel about the proper
> > calling convention, because the glibc code is frankly not readable in
> > this regard.
> 
> you HAVE to use the location as specified with the AT_SYSINFO elf flag.
> The kernel is free to move this address around between builds, as long
> as AT_SYSINFO gives the address for the location.
> 

... which quite frankly kind of bites :(

	-hpa
-- 
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