Subject: Re: VFP, PTRACE and ELF
To: None <>
From: Jason R Thorpe <>
List: tech-kern
Date: 02/14/2002 08:49:20
On Thu, Feb 14, 2002 at 11:26:57AM +0000, Richard Earnshaw wrote:

 > Before we finally switch the ARM ports to ELF I think we need to decide 
 > how a process that is using the PTRACE interface should get the VFP 
 > registers on a machine that has a VFP unit (or emulator) attached.
 > Has a similar issue (of modifying the "struct reg" or "struct fpreg" 
 > layout) come up on other ports?  If I add extra space to the end of struct 
 > fpreg will it break existing applications that try to read or write the 
 > fpreg structure via ptrace()?
 > If so, is there a way to add new calls to the ptrace interface to read and 
 > write the additional registers?

Look at how the i386 port deals with XMM registers.  A similar trick
can be used for ARM VFP.

        -- Jason R. Thorpe <>