Date: Wed, 23 Jan 2019 00:19:54 -0800 From: Mark Millard <marklmi@yahoo.com> To: John Baldwin <jhb@freebsd.org> Cc: "freebsd-ppc@freebsd.org" <freebsd-ppc@FreeBSD.org> Subject: Re: GDB TLS testing [actually running some tests finally: a success with -pthread used] Message-ID: <52E66D9B-C332-4565-B8E7-F54F6454B062@yahoo.com> In-Reply-To: <B07EC3F9-6C08-4B5D-89D0-4048AF305A2D@yahoo.com> References: <b0f5b62f-54fb-309f-a578-7b4d9e340a55@FreeBSD.org> <19343397-859C-4629-A4A5-B0DCDE25957B@yahoo.com> <AB56B3D1-1762-4115-B7B4-91D4B997F1C4@yahoo.com> <eff896f3-e385-9a12-5132-3884e69689ca@FreeBSD.org> <D0B83B01-5428-42F0-B785-221826AF7EC4@yahoo.com> <a1da2471-535d-1497-ddf3-93aa0d29df59@FreeBSD.org> <5AA68ED2-2615-438B-A6AE-406CBD8E49F7@yahoo.com> <20027C29-0093-4001-A135-23783F8B87F3@yahoo.com> <4048D2A4-7E14-481C-9B5D-00567BCF4463@yahoo.com> <2AAC9738-73BD-475A-888A-252EE853A5C6@yahoo.com> <493AC0BE-3EC6-42B7-B027-FFB6454761B5@yahoo.com> <B07EC3F9-6C08-4B5D-89D0-4048AF305A2D@yahoo.com>
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On 2019-Jan-22, at 22:53, Mark Millard <marklmi@yahoo.com> wrote:
> On 2019-Jan-22, at 19:19, Mark Millard <marklmi at yahoo.com> wrote:
>=20
>=20
>=20
>> On 2019-Jan-22, at 18:32, Mark Millard <marklm at yahoo.com> wrote:
>>=20
>>=20
>>=20
>>> On 2019-Jan-22, at 17:06, Mark Millard <marklmi at yahoo.com> wrote:
>>>=20
>>>=20
>>>=20
>>> . . .
>>> So I'm trying:
>>>=20
>>> # git clean -f
>>> # rm */config.cache */*/config.cache
>>> # env CPATH=3D/usr/local/include ./configure
>>> . . .
>>> # env CPATH=3D/usr/local/include gmake
>>> . . .
>>>=20
>>> in order to try to add paths after the command line -I paths.
>>>=20
>>> . . . This looks like it built. I've not used the build yet.
>>>=20
>>=20
>> Looking at a *.core did not go well for my context:
>>=20
>> # cc -g -O2 tls_gdb_test.c=20
>> tls_gdb_test.c:16:2: warning: indirection of non-volatile null =
pointer will be deleted, not trap [-Wnull-dereference]
>> *(char *)NULL =3D 1;
>> ^~~~~~~~~~~~~
>> tls_gdb_test.c:16:2: note: consider using __builtin_trap() or =
qualifying pointer with 'volatile'
>> 1 warning generated.
>> . . .
>=20
>=20
> So far all tried-combinations of using gcc versions for build
> the test program and/or building the gdb used do not work for
> "p id" and "p &id" in doing the test. clang is not essential
> to the behavior observed.
Using "-g -O2 -pthread" to build the test program via system
clang or gcc8 (for example) did lead to the likes of:
(gdb) run=20
Starting program: /root/c_tests/a.out=20
main: PID 15350
id =3D 15350 (0x810055020)
^C
Program received signal SIGINT, Interrupt.
main (ac=3D<optimized out>, av=3D<optimized out>) at tls_gdb_test.c:16
16 *(char *)NULL =3D 1;
(gdb) bt
#0 main (ac=3D<optimized out>, av=3D<optimized out>) at =
tls_gdb_test.c:16
(gdb) info threads
Id Target Id Frame=20
* 1 LWP 100324 of process 15350 main (ac=3D<optimized out>, =
av=3D<optimized out>) at tls_gdb_test.c:16
(gdb) p id
$1 =3D 15350
(gdb) p &id
$2 =3D (int *) 0x810055020
So it appears one branch of:
static void
fbsd_fetch_rtld_offsets (struct gdbarch *gdbarch, struct =
fbsd_pspace_data *data)
{
TRY
{
/* Fetch offsets from debug symbols in rtld. */
data->off_linkmap =3D parse_and_eval_long ("&((Obj_Entry =
*)0)->linkmap");
data->off_tlsindex =3D parse_and_eval_long ("&((Obj_Entry =
*)0)->tlsindex");
data->rtld_offsets_valid =3D true;
return;
}
CATCH (e, RETURN_MASK_ERROR)
{
data->off_linkmap =3D -1;
}
END_CATCH
TRY
{
/* Fetch offsets from global variables in libthr. Note that
this does not work for single-threaded processes that are not
linked against libthr. */
data->off_linkmap =3D fbsd_read_integer_by_name(gdbarch,
=
"_thread_off_linkmap");
data->off_tlsindex =3D fbsd_read_integer_by_name(gdbarch,
=
"_thread_off_tlsindex");
data->rtld_offsets_valid =3D true;
return;
}
CATCH (e, RETURN_MASK_ERROR)
{
data->off_linkmap =3D -1;
}
END_CATCH
}
is working when -pthread is used.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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