[lldb-dev] register read on 32-bit Linux

Thirumurthi, Ashok ashok.thirumurthi at intel.com
Fri Aug 23 07:59:35 PDT 2013

Go for it, Michael!

FYI, the x86_64 build of LLDB will have limited success with i386 inferiors, but it's a pretty good starting point (i.e. test/functionalities/registers passes).  In this case, ptrace calls populate the 64-bit register set, and the RegisterContext_x86_64 class uses offsetof to associate the i386 register set with the LS bytes of the associated 64-bit registers.  However, this isn't correct because "The DWARF and GCC register numbers need to use the i386 register numbering schemes otherwise all info parsed from EH frame and DWARF will be incorrect when they don't match up. - Greg Clayton".

The i386 build of LLDB should use RegisterContext_i386.  Similarly, a future remote i386 target should use RegisterContext_i386.  However, this class is just stubbed in.

An eventual goal is to abstract a dynamic register set that can be used consistently for native local and remote debugging in a platform-independent manner.  Also, for core file support across platforms, we'll want a register set hierarchy that is distinct from platform dependencies like ProcessMonitor.  This was implemented for MachO, and Greg provided a skeleton patch for this purpose on the lists.  Cheers,

-        Ashok

From: lldb-dev-bounces at cs.uiuc.edu [mailto:lldb-dev-bounces at cs.uiuc.edu] On Behalf Of Michael Sartain
Sent: Friday, August 23, 2013 12:49 AM
To: lldb-dev at cs.uiuc.edu
Subject: [lldb-dev] register read on 32-bit Linux

This is currently calling into the POSIX RegisterContext_x86_64 and returning all the 64-bit registers.

I'm guessing this is known already. Curious if someone is already working on this or has a plan for fixing it before I jump in?

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