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Re: new syscall stub support for ia64 libc

From: Roland McGrath <roland at redhat dot com>
To: Jakub Jelinek <jakub at redhat dot com>
Cc: davidm at hpl dot hp dot com, libc-hacker at sources dot redhat dot com
Date: Thu, 30 Oct 2003 11:37:56 -0800
Subject: Re: new syscall stub support for ia64 libc

> Can you readelf -Wl arch/ia64/kernel/gate.so |grep LOAD (or grep -A1 LOAD
> instead), or better yet readelf -Wa arch/ia64/kernel/gate.so ? I'd like
> to understand why you need the second LOAD segment, what stuff has it in
> etc.

There are two LOAD segments for the same one page of file data mapped into
two consecutive pages with different permissions.  The first segment is
read-only and the second is execute-only.  The execute-only permission
(cannot be read by user mode) is required for the magic EPC instruction.
Hence we need two mappings to see the DSO info and to execute.

> IMHO NEED_DL_SYSINFO should be defined in both NPTL and
> Linuxthread ia64/dl-sysdep.h, while USE_DL_SYSINFO only in NPTL.
> And sysdep.h should use sysinfo only if USE_DL_SYSINFO is defined.
> Then linuxthreads will work just fine (use break always, who cares)
> and NPTL will use VDSO.

Agreed.  THis is what i386 does.

References:
- Re: new syscall stub support for ia64 libc
  - From: Jakub Jelinek

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