Re: GDB TLS testing [actually running some tests finally: a success with -pthread used]
John Baldwin <[email protected]>
| Newsgroups | gmane.os.freebsd.devel.ppc |
|---|---|
| Message-ID | <[email protected]> |
On 1/23/19 10:10 AM, Mark Millard wrote: > > > On 2019-Jan-23, at 09:59, Mark Millard <marklmi at yahoo.com> wrote: > > > >> On 2019-Jan-23, at 09:02, John Baldwin <jhb at FreeBSD.org> wrote: >> >>> On 1/23/19 12:19 AM, Mark Millard wrote: >>>> >>>> >>>> On 2019-Jan-22, at 22:53, Mark Millard <[email protected]> wrote: >>>> >>>> >>>> >>>>> On 2019-Jan-22, at 19:19, Mark Millard <marklmi at yahoo.com> wrote: >>>>> >>>>> >>>>> >>>>>> On 2019-Jan-22, at 18:32, Mark Millard <marklm at yahoo.com> wrote: >>>>>> >>>>>> >>>>>> >>>>>>> On 2019-Jan-22, at 17:06, Mark Millard <marklmi at yahoo.com> wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> . . . >>>>>>> So I'm trying: >>>>>>> >>>>>>> # git clean -f >>>>>>> # rm */config.cache */*/config.cache >>>>>>> # env CPATH=/usr/local/include ./configure >>>>>>> . . . >>>>>>> # env CPATH=/usr/local/include gmake >>>>>>> . . . >>>>>>> >>>>>>> in order to try to add paths after the command line -I paths. >>>>>>> >>>>>>> . . . This looks like it built. I've not used the build yet. >>>>>>> >>>>>> >>>>>> Looking at a *.core did not go well for my context: >>>>>> >>>>>> # cc -g -O2 tls_gdb_test.c >>>>>> tls_gdb_test.c:16:2: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference] >>>>>> *(char *)NULL = 1; >>>>>> ^~~~~~~~~~~~~ >>>>>> tls_gdb_test.c:16:2: note: consider using __builtin_trap() or qualifying pointer with 'volatile' >>>>>> 1 warning generated. >>> >>> For me, builtin_trap didn't DTRT on ppc before, but that was probably using >>> gcc rather than clang (and possibly using gcc4.2). >>> >>>>>> . . . >>>>> >>>>> >>>>> 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 >>>> Starting program: /root/c_tests/a.out >>>> main: PID 15350 >>>> id = 15350 (0x810055020) >>>> >>>> ^C >>>> Program received signal SIGINT, Interrupt. >>>> main (ac=<optimized out>, av=<optimized out>) at tls_gdb_test.c:16 >>>> 16 *(char *)NULL = 1; >>>> (gdb) bt >>>> #0 main (ac=<optimized out>, av=<optimized out>) at tls_gdb_test.c:16 >>>> (gdb) info threads >>>> Id Target Id Frame >>>> * 1 LWP 100324 of process 15350 main (ac=<optimized out>, av=<optimized out>) at tls_gdb_test.c:16 >>>> (gdb) p id >>>> $1 = 15350 >>>> (gdb) p &id >>>> $2 = (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 = parse_and_eval_long ("&((Obj_Entry *)0)->linkmap"); >>>> data->off_tlsindex = parse_and_eval_long ("&((Obj_Entry *)0)->tlsindex"); >>>> data->rtld_offsets_valid = true; >>>> return; >>>> } >>>> CATCH (e, RETURN_MASK_ERROR) >>>> { >>>> data->off_linkmap = -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 = fbsd_read_integer_by_name(gdbarch, >>>> "_thread_off_linkmap"); >>>> data->off_tlsindex = fbsd_read_integer_by_name(gdbarch, >>>> "_thread_off_tlsindex"); >>>> data->rtld_offsets_valid = true; >>>> return; >>>> } >>>> CATCH (e, RETURN_MASK_ERROR) >>>> { >>>> data->off_linkmap = -1; >>>> } >>>> END_CATCH >>>> } >>>> >>>> is working when -pthread is used. >>> >>> Yes. The second one only works for programs linked against -lthr. Otherwise >>> you need to have built your system with debug symbols (which is the default), >>> and gdb needs to be able to access /usr/lib/debug/libexec/ld-elf.so.1.debug >>> to determine the offsets of the two fields in Obj_Entry (this is what the >>> first TRY clause does). >> >> I buildworld buildkernel with debug symbols for both and install them: >> >> # ls -lT /usr/lib/debug/libexec/ld-elf.so.1.debug >> -r--r--r-- 1 root wheel 576344 Dec 11 22:58:11 2018 /usr/lib/debug/libexec/ld-elf.so.1.debug >> >> # ls -lT /usr/libexec/ld-elf.so.1 /libexec/ld-elf.so.1 >> -r-xr-xr-x 1 root wheel 184400 Dec 9 02:35:05 2018 /libexec/ld-elf.so.1 >> lrwxr-xr-x 1 root wheel 25 Dec 11 22:58:12 2018 /usr/libexec/ld-elf.so.1 -> ../../libexec/ld-elf.so.1 >> >> So I think the first TRY clause does not work. >> >> In the tested gdb used on the a.out I'm testing I get: >> >> (gdb) p &((Obj_Entry *)0)->linkmap >> No symbol "Obj_Entry" in current context. >> >> gdb does not report reading symbols from or for: >> >> /usr/lib/debug/libexec/ld-elf.so.1.debug >> or: >> /usr/libexec/ld-elf.so.1 >> or: >> /libexec/ld-elf.so.1 >> >> It only reports reading them from/for the a.out . > > It neded up that I had a littel time so . . . > > I tried /usr/local/bin/gdb and for it: > > (gdb) p &((Obj_Entry *)0)->linkmap > $1 = (struct link_map *) 0x238 > > So the lack of finding Obj_Entry via the test gdb seems to be > specific to the test gdb, not a problem for devel/gdb . > > May be the test gdb has some sort of build problem in my context, > given that I used CPATH to get things to build? Oh, it might not have /usr/lib/debug configured as a debug directory. I usually use a wrapper script (available at github/bsdjhb/kdbg.git/gdb/build) which sets various configure options to match what the port does. One of those is --with-separate-debug-dir=/usr/lib/debug which will probably fix this. -- John Baldwin _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-ppc To unsubscribe, send any mail to "[email protected]"