Re: unwind support for Linux 2.6 vsyscall DSO

[Daniel Jacobowitz <drow@mvista.com>]

On Wed, Oct 08, 2003 at 05:00:36PM -0400, Andrew Cagney wrote:
> >>- unpack an architecture's auxv
> >>- pack an architecture's auxv
> >
> >
> >This in fact differs with byte order and word size, not further by target.
> >So a generic utility function suffices for this.  If the responsibility for
> >packing and unpacking is in each target, they should all be able to use the
> >same utility function and stay about as simple as the block-reading target
> >code.  If the responsibility for unpacking lies with the caller of the
> >target function, then the single utility function suffices for all callers
> >(since then there is never a need for packing, only unpacking).
> 
> Unfortunatly, things aren't so simple :-(
> 
> Solaris:
> #define AT_DCACHEBSIZE  10      /* smallest data cache block size */
> #define AT_ICACHEBSIZE  11      /* smallest instruction cache block size */
> #define AT_UCACHEBSIZE  12      /* smallest unified cache block size */
> ...
> 
> GNU/Linux:
> #define AT_NOTELF 10    /* program is not ELF */
> #define AT_UID    11    /* real uid */
> #define AT_EUID   12    /* effective uid */
> ...
> 
> As with signals, the attribute indexes are per-os (and potentially per 
> ISA).  So core code will need to define an OS independant set of enums 
> and then map that onto the real numbers.
> 
> If I understand things correctly, the two driving needs are:
> 
> - being able to extract the value of AT_ENTRY, and AT_LINUX_<vsyscall 
> address>
> 
> - being able to obtain the entire AUXV so that it can be saved in a core 
> file
> 
> Would a per-os (technically per-architecture) SVR4 auxv lookup method 
> that was implement using a fixed to_query() work?

Sounds more or less good to me.  I don't think we need a generic
gdbarch method for querying auxv; more something like a
gdbarch_auxv_entry_point () and a gdbarch_auxv_sysinfo_dso_address ()?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer