[PATCH] RISC-V: Don't use ps_get_thread_area in libthread_db (bug 23402)

[Palmer Dabbelt]

On Fri, 27 Jul 2018 16:28:06 PDT (-0700), dj@redhat.com wrote:
>
> Andreas Schwab <schwab@suse.de> writes:
>> Since RISC-V stores the thread pointer in a general register libthread_db
>> can just ask the debugger for the register contents instead of trying to
>> call ps_get_thread_area.  This enables thread debugging in gdb.
>>
>> 	* sysdeps/riscv/nptl/tls.h (DB_THREAD_SELF): Use REGISTER instead
>> 	of CONST_THREAD_AREA.
>
> I'm OK with this but... will the definition be the same for riscv32 ?

It looks like this got lost in the shuffle, but as far as I can tell it makes 
sense.  Is anyone opposed to this, which differs only in the comment?

    commit 6a54cad00025f1513068c161e332434b9556293b
    gpg: Signature made Fri 03 Aug 2018 02:35:12 PM PDT
    gpg:                using RSA key 00CE76D1834960DFCE886DF8EF4CA1502CCBAB41
    gpg:                issuer "palmer@dabbelt.com"
    gpg: Good signature from "Palmer Dabbelt <palmer@dabbelt.com>" [ultimate]
    gpg:                 aka "Palmer Dabbelt <palmer@sifive.com>" [ultimate]
    Author: Andreas Schwab <schwab@suse.de>
    Date:   Thu Jul 12 09:24:36 2018 +0200

        RISC-V: Don't use ps_get_thread_area in libthread_db (bug 23402)

        Since RISC-V stores the thread pointer in a general register libthread_db
        can just ask the debugger for the register contents instead of trying to
        call ps_get_thread_area.  This enables thread debugging in gdb.

                * sysdeps/riscv/nptl/tls.h (DB_THREAD_SELF): Use REGISTER instead
                of CONST_THREAD_AREA.

    diff --git a/sysdeps/riscv/nptl/tls.h b/sysdeps/riscv/nptl/tls.h
    index 7745d5904455..a82fd71488c9 100644
    --- a/sysdeps/riscv/nptl/tls.h
    +++ b/sysdeps/riscv/nptl/tls.h
    @@ -99,9 +99,10 @@ typedef struct
     # define TLS_DEFINE_INIT_TP(tp, pd) \
       void *tp = (void *) (pd) + TLS_TCB_OFFSET + TLS_PRE_TCB_SIZE

    -/* Magic for libthread_db to know how to do THREAD_SELF.  */
    +/* Informats libthread_db that the therad pointer is register 4, which is used
    + * to to know how to do THREAD_SELF.  */
     # define DB_THREAD_SELF \
    -  CONST_THREAD_AREA (32, TLS_TCB_OFFSET + TLS_PRE_TCB_SIZE)
    +  REGISTER (64, 64, 4 * 8, - TLS_TCB_OFFSET - TLS_PRE_TCB_SIZE)

     /* Access to data in the thread descriptor is easy.  */
     # define THREAD_GETMEM(descr, member) \