Re: unwind support for Linux 2.6 vsyscall DSO

[Roland McGrath <roland@redhat.com>]

> I think so, on Solaris some of the AT_* values in <sys/auxv.h> don't
> match those in <elf.h> on linux and those in
> gdb/../include/elf/elf.h. The AT_SYSINFO_EHDR seems to be 33 on all of
> those, but other values are different. If we want to extend the auxv
> handling to recognize more types, we may run into problems. 

Perhaps you overlooked my explanation of all this on Monday:

  However, the AT_* values (except for AT_NULL==0) are neither standardized
  nor de facto reliably the same across operating systems (they are part of
  the SVR4 ABI spec for each processor I believe).  The values in
  include/elf/common.h are copied from glibc's <elf.h>, and are what GNU/Linux
  uses.  Some of the values used on Solaris conflict, though Sun seems to have
  taken to using AT_SUN_* names and values >=2000 for recent additions and so
  it now seems unlikely they will use values 32 or 33 and thus risk false
  matches with the Linux AT_SYSINFO_EHDR tag.  (FYI, NetBSD's elf.h header has
  all of Sun's values and no GNU/Linux values; however NetBSD itself uses only
  the tags <10 which in fact match exactly everywhere.)

Any use of auxv tags will always be OS-specific.  There is no universal
generic set to translate them to or anything like that.  The fact that
there is an aux vector in a given format with tags and values is common
code worth sharing across platforms, but that is all.