Re: [PATCH v2] gdb: CTF support

[Weimin Pan <weimin.pan@oracle.com>]

Hi Simon,

On 9/21/2019 3:21 PM, Simon Marchi wrote:
> Hi Weimin,
>
> I'd like to give this a try and review this, but I hit a wall.  I compiled
> gcc with this patch series (v5) applied:
>
>    https://gcc.gnu.org/ml/gcc-patches/2019-09/msg00457.html
>
> I am able to compile a simple .c file with -gt, and the resulting
> binary contains a .ctf section.  But when loading the file in GDB,
> I get this:
>
>    (gdb) file a.out
>    Reading symbols from a.out...
>    ctf_bfdopen failed on /home/simark/build/binutils-gdb/gdb/a.out - File data structure corruption detected
>
> The error occurs in ctf_bufopen, at line 1294:
>
>    1294	  if (hp.cth_lbloff > hp.cth_objtoff
>    1295	      || hp.cth_objtoff > hp.cth_funcoff
>    1296	      || hp.cth_funcoff > hp.cth_typeoff
>    1297	      || hp.cth_funcoff > hp.cth_varoff
>    1298	      || hp.cth_varoff > hp.cth_typeoff || hp.cth_typeoff > hp.cth_stroff)
>    1299	    return (ctf_set_open_errno (errp, ECTF_CORRUPT));
>
> `hp` is:
>
>    $10 = {
>      cth_preamble = {
>        ctp_magic = 57330,
>        ctp_version = 4 '\004',
>        ctp_flags = 0 '\000'
>      },
>      cth_parlabel = 0,
>      cth_parname = 0,
>      cth_lbloff = 10,
>      cth_objtoff = 0,
>      cth_funcoff = 0,
>      cth_varoff = 0,
>      cth_typeoff = 12,
>      cth_stroff = 12,
>      cth_strlen = 16
>    }
>
> The program I compiled is:
>
>    int main() {
>        return 2;
>   }
>
> compiled with:
>
>    /data/scratch/gcc-install/bin/gcc test.c -gt -O0

Looks like you're using the latest gcc patch with current upstream binutils.
Unfortunately, these two are not compatible since the latter lacks two newer
header fields and the ability to transparently upgrade the ctf header. The
same problem can be reproduced with "readelf" from binutils master:

% readelf --ctf=".ctf" a.out
readelf: Error: CTF open failure: File data structure corruption detected

Please try applying the linker patch series that NicK posted on Sep 6 to
binutils, under the name of "CTF linking support", as mentioned in the
gcc patch sited above:

NickA recently posted a changeset to the binutils mailing list that adds
initial support for linking CTF sections. Please see

https://sourceware.org/ml/binutils/2019-09/msg00045.html

( This current GCC  patch set has the ctf.h in sync with the above-mentioned
    binutils patch set. )

which should fix this problem.

> On 2019-07-30 7:43 p.m., Weimin Pan wrote:
>> [Changes from v1:
>>   - Add libctf dependencies in Makefile.def and Makefile.in.
>>   - Use type-safe registry API for per-objfile data ctf_tid_key.
>>   - Replace buildsym-legacy.h with buildsym.h.
>>   - Use xcalloc/xfree to allocate hash tables.
>>   - Use get_global_symbols() instead of get_file_symbols() to add symbols.
>>   - Rename gdb/ctf.h to /gdb/tracectf.h.]
> Could you please rename ctf.c to tracectf.c as well?  It's much easier when the
> corresponding .c and .h are named the same way.  I'd also like if you did that
> renaming it a separate, preparatory patch, just to keep each patch focused.

Good idea (there seemed to be some confusion about "ctf.c" at GNU Tools 
Cauldron 2019.) Will do it separately.

Thank you very much for taking the time.

Weimin

>
> Simon