Re: [PATCH 05/11] Internal TLS support for aarch64, x86_64, riscv, ppc64, and s390x

[Kevin Buettner <kevinb@redhat.com>]

On Fri, 11 Oct 2024 09:12:55 +0100
Luis Machado <luis.machado@arm.com> wrote:

> Thanks for the patch.
> 
> On 10/10/24 03:16, Kevin Buettner wrote:
> > For each architecture, aarch64, x86_64, riscv, ppc64, and s390x,
> > this commit defines a suitable 'get_tls_dtv_addr' method and,
> > when necessary, a 'get_tls_dtp_offset' method.
> > 
> > It also registers linux_get_thread_local_address, defined in
> > linux-tdep.c (in an earlier commit), as the get_thread_local_address
> > gdbarch method.  It also registers its architecture specific code
> > using linux_register_tls_methods().
> > 
> > Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=24548
> > Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31563
> > ---
> >  gdb/aarch64-linux-tdep.c | 53 +++++++++++++++++++++++++++
> >  gdb/amd64-linux-tdep.c   | 37 +++++++++++++++++++
> >  gdb/ppc-linux-tdep.c     | 62 ++++++++++++++++++++++++++++++++
> >  gdb/riscv-linux-tdep.c   | 78 ++++++++++++++++++++++++++++++++++++++++
> >  gdb/s390-linux-tdep.c    | 43 ++++++++++++++++++++++
> >  5 files changed, 273 insertions(+)
> > 
> > diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
> > index c608a84bc71..b03c2162a1a 100644
> > --- a/gdb/aarch64-linux-tdep.c
> > +++ b/gdb/aarch64-linux-tdep.c
> > @@ -35,6 +35,7 @@
> >  #include "target/target.h"
> >  #include "expop.h"
> >  #include "auxv.h"
> > +#include "inferior.h"
> >  
> >  #include "regcache.h"
> >  #include "regset.h"
> > @@ -2693,6 +2694,55 @@ aarch64_use_target_description_from_corefile_notes (gdbarch *gdbarch,
> >    return true;
> >  }
> >  
> > +/* Fetch and return the TLS DTV (dynamic thread vector) address for PTID.
> > +   Throw a suitable TLS error if something goes wrong.  */
> > +
> > +static CORE_ADDR
> > +aarch64_linux_get_tls_dtv_addr (struct gdbarch *gdbarch, ptid_t ptid,
> > +				linux_libc libc)
> > +{
> > +  /* On aarch64, the thread pointer is found in the tpidr register.  */
> > +  regcache *regcache
> > +    = get_thread_arch_regcache (current_inferior (), ptid, gdbarch);
> > +  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
> > +  target_fetch_registers (regcache, tdep->tls_regnum_base);
> > +  ULONGEST thr_ptr;
> > +  if (regcache->cooked_read (tdep->tls_regnum_base, &thr_ptr) != REG_VALID)  
> 
> Since we're relying on TPIDR now, might be worth mentioning it is currently the
> first register in the TLS feature. Just in case things change later on?

I've changed the relevant comment in my local sources to read as follows:

  /* On aarch64, the thread pointer is found in the TPIDR register. 
     Note that this is the first register in the TLS feature - see
     features/aarch64-tls.c - and it will always be present.  */

Kevin