[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=11804

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ich at az2000 dot de

--- Comment #14 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-07-28 06:19:18 UTC ---
*** Bug 9904 has been marked as a duplicate of this bug. ***

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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=11804

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.kratochvil at redhat
                   |                            |dot com
            Version|unknown                     |HEAD

--- Comment #15 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-07-28 07:06:53 UTC ---
[PATCH] refreshed patch for PR 11804 and PR 9904
http://sourceware.org/ml/gdb-patches/2012-07/msg00249.html
From: Jean-Marc Saffroy <saffroy at gmail dot com>

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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[cvs-commit at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=11804

--- Comment #16 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> 2012-08-07 13:26:39 UTC ---
CVSROOT:    /cvs/src
Module name:    src
Changes by:    jkratoch@sourceware.org    2012-08-07 13:26:33

Modified files:
    gdb            : ChangeLog defs.h fbsd-nat.c gcore.c gnu-nat.c 
                     linux-tdep.c procfs.c 
    gdb/testsuite  : ChangeLog 
Added files:
    gdb/testsuite/gdb.base: gcore-relro-lib.c gcore-relro-main.c 
                            gcore-relro.exp 

Log message:
    gdb/
    PR 11804
    * defs.h (find_memory_region_ftype): New comment.  New arg modified.
    * fbsd-nat.c (fbsd_find_memory_regions): Add the passed modified value.
    * gcore.c (gcore_create_callback): New function comment.  Add modified
    parameter.  Only write modified regions.  Set SEC_READONLY exactly
    according to MODIFIED.
    (objfile_find_memory_regions): Ignore separate debug info files.  Ass
    the passed modified value to FUNC.
    * gnu-nat.c (gnu_find_memory_regions): Add the passed modified value.
    * linux-tdep.c (linux_find_memory_regions): Try to reads smaps file
    first.  New variables modified and has_anonymous.  Parse the lines of
    smaps file.  Add the passed MODIFIED value to FUNC.
    * procfs.c (find_memory_regions_callback): Add the passed modified
    value.

    gdb/testsuite/
    PR 11804
    * gdb.base/gcore-relro.exp: New file.
    * gdb.base/gcore-relro-main.c: New file.
    * gdb.base/gcore-relro-lib.c: New file.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&r1=1.14563&r2=1.14564
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/defs.h.diff?cvsroot=src&r1=1.320&r2=1.321
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/fbsd-nat.c.diff?cvsroot=src&r1=1.26&r2=1.27
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/gcore.c.diff?cvsroot=src&r1=1.52&r2=1.53
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/gnu-nat.c.diff?cvsroot=src&r1=1.79&r2=1.80
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/linux-tdep.c.diff?cvsroot=src&r1=1.21&r2=1.22
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/procfs.c.diff?cvsroot=src&r1=1.159&r2=1.160
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/ChangeLog.diff?cvsroot=src&r1=1.3328&r2=1.3329
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.base/gcore-relro-lib.c.diff?cvsroot=src&r1=NONE&r2=1.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.base/gcore-relro-main.c.diff?cvsroot=src&r1=NONE&r2=1.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.base/gcore-relro.exp.diff?cvsroot=src&r1=NONE&r2=1.1

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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=11804

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #17 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-08-07 13:27:59 UTC ---
Checked in.

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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2010-09-09 21:40 -------
(In reply to comment #12)
> Yeah - I've bounced it to our kernel folks.

Any follow-up would be great, before pinging it for FSF GDB, thanks.


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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 14:10 -------
> (In reply to comment #10)
> > Hm.  The .dynamic section in memory is different from that in the file-backing
> > (at least DT_DEBUG has been filled in by the dynamic loader).  But still the
> > page is marked clean in /proc/smaps.
> 
> I have tested this on Fedora14snapshot + kernel-2.6.33.6-147.fc13.x86_64
> and it works for me.
> 
> ./gdb -nx /usr/libexec/postfix/qmgr
> GNU gdb (GDB) 7.2.50.20100831-cvs
> [...]
> This GDB was configured as "x86_64-unknown-linux-gnu".
> [...]
> Reading symbols from /usr/libexec/postfix/qmgr...(no debugging symbols
> found)...done.
> (gdb) start
> Temporary breakpoint 1 at 0x8ae0
> Starting program: /usr/libexec/postfix/qmgr
> [Thread debugging using libthread_db enabled]
> Temporary breakpoint 1, 0x00007ffff7fbdae0 in main ()
> (gdb) info files
>         `/usr/libexec/postfix/qmgr', file type elf64-x86-64.
> [...]
>         0x00007ffff81ff940 - 0x00007ffff81ffba0 is .dynamic
> 
> 7ffff81fe000-7ffff8200000 r--p 00049000 fd:01 6523997                   
> /usr/libexec/postfix/qmgr
> Size:                  8 kB
> Rss:                   8 kB
> Pss:                   8 kB
> Shared_Clean:          0 kB
> Shared_Dirty:          0 kB
> Private_Clean:         0 kB
> Private_Dirty:         8 kB
> Referenced:            8 kB
> Swap:                  0 kB
> KernelPageSize:        4 kB
> MMUPageSize:           4 kB
> 
> unpatched:
>   [92] load              NOBITS          00007ffff81fe000 115dec 002000 00   A 
> 0   0  1
> 
> patched:
>   [92] load              PROGBITS        00007ffff81fe000 002000 00   A  0   0  1
> 
> Thanks for the testing, though.
> 
> From your dumps I believe your .dynamic was at 0x7fac68cc1bc0 and its DT_DEBUG
> was at 0x7fac68cc1d18 which would suggest there is some problem in Linux
> kernel's content of /proc/PID/smaps.

Yeah - I've bounced it to our kernel folks.  New started processes work fine,
but a lot of old processes on my system have lost the dirty bits in
/proc/smaps ... let's see what their response will be.


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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2010-08-31 14:06 -------
(In reply to comment #7)
> And in the core file:
>   [67] load              NOBITS           00007fac68cc1000  000ed558
>        0000000000001000  0000000000000000   A       0     0     1

Not sure what you have meant but there is NOBITS, therefore it is _not_ present
in the core file.

(In reply to comment #9)
> OTOH a recent 7.1 tree looks much different (but has the same logic and
> also doesn't work for me - but it lost the nice debugging stuff).

Sorry but I am not going to support the former Jeff Johnston's PIE patch magic.
Also there were some post-7.1 PIE fixes, suggesting just to use FSF GDB HEAD as
there will be even still one PIE bug in FSF GDB 7.2.
http://sourceware.org/ml/gdb-patches/2010-07/msg00237.html


(In reply to comment #10)
> Hm.  The .dynamic section in memory is different from that in the file-backing
> (at least DT_DEBUG has been filled in by the dynamic loader).  But still the
> page is marked clean in /proc/smaps.

I have tested this on Fedora14snapshot + kernel-2.6.33.6-147.fc13.x86_64
and it works for me.

./gdb -nx /usr/libexec/postfix/qmgr
GNU gdb (GDB) 7.2.50.20100831-cvs
[...]
This GDB was configured as "x86_64-unknown-linux-gnu".
[...]
Reading symbols from /usr/libexec/postfix/qmgr...(no debugging symbols
found)...done.
(gdb) start
Temporary breakpoint 1 at 0x8ae0
Starting program: /usr/libexec/postfix/qmgr
[Thread debugging using libthread_db enabled]
Temporary breakpoint 1, 0x00007ffff7fbdae0 in main ()
(gdb) info files
        `/usr/libexec/postfix/qmgr', file type elf64-x86-64.
[...]
        0x00007ffff81ff940 - 0x00007ffff81ffba0 is .dynamic

7ffff81fe000-7ffff8200000 r--p 00049000 fd:01 6523997                   
/usr/libexec/postfix/qmgr
Size:                  8 kB
Rss:                   8 kB
Pss:                   8 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         8 kB
Referenced:            8 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB

unpatched:
  [92] load              NOBITS          00007ffff81fe000 115dec 002000 00   A 
0   0  1

patched:
  [92] load              PROGBITS        00007ffff81fe000 002000 00   A  0   0  1

Thanks for the testing, though.

>From your dumps I believe your .dynamic was at 0x7fac68cc1bc0 and its DT_DEBUG
was at 0x7fac68cc1d18 which would suggest there is some problem in Linux
kernel's content of /proc/PID/smaps.


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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 13:31 -------
Hm.  The .dynamic section in memory is different from that in the file-backing
(at least DT_DEBUG has been filled in by the dynamic loader).  But still the
page is marked clean in /proc/smaps.

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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 12:52 -------
In my gdb copy (7.0 based), the following looks suspicious:

    if (dyn_tag == dyntag)
      {
        /* If requested, try to read the runtime value of this .dynamic
           entry.  */
        if (ptr)
          {
            gdb_byte ptr_buf[8];
            CORE_ADDR ptr_addr;
            int got;

            ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;

                                                  ^^^^^^^^^^^^^^^^^

            if (ptr != NULL)
              {
                if (debug_solib)
                  fprintf_unfiltered (gdb_stdlog,
                                      "elf_locate_base: unrelocated ptr addr %s\n",
                                      paddress (target_gdbarch, ptr_addr));


I can see the dynamic section contents just fine at dyn_addr + (buf - bufstart).
OTOH a recent 7.1 tree looks much different (but has the same logic and
also doesn't work for me - but it lost the nice debugging stuff).

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[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 12:07 -------
The executable is built with -fPIE, but there seem to be relocations in the
respective page:

Relocation section '.rela.dyn' at offset 0x25d0 contains 133 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
00000020f740  000000000008 R_X86_64_RELATIVE                    000000000000d96e
00000020f760  000000000008 R_X86_64_RELATIVE                    000000000000bf88
...
00000020fb10  008e00000001 R_X86_64_64       00000000002103e0 var_dest_rate_dela
y + 0
00000020fb50  008a00000001 R_X86_64_64       0000000000210400 var_defer_xports +
 0
00000020fb70  008000000001 R_X86_64_64       0000000000210438 var_conc_pos_feedb
ack + 0
00000020fb90  00ac00000001 R_X86_64_64       00000000002103f8 var_conc_neg_feedb
ack + 0
00000020fe38  000b00000006 R_X86_64_GLOB_DAT 0000000000000000 var_daemon_timeout
 + 0


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------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 11:52 -------
And in the core file:

  [67] load              NOBITS           00007fac68cc1000  000ed558
       0000000000001000  0000000000000000   A       0     0     1


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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 11:45 -------
Hm, it _is_ in the core-file:

Save segment, 4096 bytes at 0x7fac68cc1000 (r  ) for                     
/usr/lib/postfix/qmgr
Save segment, 4096 bytes at 0x7fac68cc1000


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[rguenth at gcc dot gnu dot org]

------- Additional Comments From rguenth at gcc dot gnu dot org  2010-08-31 11:26 -------
Hm, it doesn't seem to work reliably for me (it works for dumping core of
/bin/sleep).  If I dump core of a running /usr/lib/postfix/qmgr on load
I get

# gdb /usr/lib/postfix/qmgr
Reading symbols from /usr/lib/postfix/qmgr...Missing separate debuginfo for
/usr/lib/postfix/qmgr
Try: zypper install -C
"debuginfo(build-id)=a67933b04330530f5e80941c968ba3623b1fd5ac"
(no debugging symbols found)...done.
(gdb) set debug solib
(gdb) set verbose
(gdb) core core.4529
svr4_current_sos: exec_bfd /usr/lib/postfix/qmgr
elf_locate_base: found program entry address 0x7fac68ab63a0 for
/usr/lib/postfix/qmgr
elf_locate_base: expected relocation offset 0x7fac68ab2000 for /usr/lib/postfix/qmgr
elf_locate_base: .dynamic section found in /usr/lib/postfix/qmgr
elf_locate_base: .dynamic addr 0x20fbc0
elf_locate_base: read in .dynamic section
elf_locate_base: tag at offset 0x0 is not readable, dropping relocation offset
0x7fac68ab2000
elf_locate_base: found program entry address 0x7fac68ab63a0 for
/usr/lib/postfix/qmgr
elf_locate_base: expected relocation offset 0x7fac68ab2000 for /usr/lib/postfix/qmgr
elf_locate_base: .dynamic section found in /usr/lib/postfix/qmgr
elf_locate_base: .dynamic addr 0x20fbc0
elf_locate_base: read in .dynamic section
elf_locate_base: tag at offset 0x0 is not readable, dropping relocation offset
0x7fac68ab2000
elf_locate_base: unrelocated ptr addr 0x20fd18
elf_locate_base: relocated ptr addr 0x20fd18 (relocation offset 0x0) for
/usr/lib/postfix/qmgr
elf_locate_base: Tag entry has value 0x0 -- return now
svr4_current_sos: no DT_DEBUG found in /usr/lib/postfix/qmgr -- return now

the program address looks good, the .dynamic section in the running process
is mapped like

7fac68cc1000-7fac68cc2000 r--p 0000f000 08:06 360346                     /usr/li
b/postfix/qmgr
Size:                  4 kB
Rss:                   4 kB
Pss:                   4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         4 kB
Private_Dirty:         0 kB
Referenced:            4 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
7fac68cc2000-7fac68cc3000 rw-p 00010000 08:06 360346                     /usr/li
b/postfix/qmgr
Size:                  4 kB
Rss:                   4 kB
Pss:                   4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         4 kB
Referenced:            4 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
7fac68cc3000-7fac68cfe000 rw-p 00000000 00:00 0                          [heap]

thus the relocated address should be not in the core file but taken from
/usr/lib/postfix/qmgr - but that fails.  Is this not available at this point
or where do I need to dig?  I'm not too familiar with the gdb codebase...

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                   |                            |org


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[Bug corefiles/11804] Fix -Wl,-z,relro gcore writer (+maybe reader)

[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2010-08-30 09:16 -------
Post:
[patch] Code cleanup: Make function typedef for find memory region
http://sourceware.org/ml/gdb-patches/2010-08/msg00498.html
[patch] Fix gcore writer for -Wl,-z,relro (PR corefiles/11804)
http://sourceware.org/ml/gdb-patches/2010-08/msg00499.html


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----------------------------------------------------------------------------
   Target Milestone|7.1                         |---


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         AssignedTo|unassigned at sourceware dot|jan dot kratochvil at redhat
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             Status|NEW                         |ASSIGNED


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[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2010-08-16 17:22 -------
Created an attachment (id=4934)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4934&action=view)
Preliminary fix (merged two parts).


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[jan dot kratochvil at redhat dot com]

------- Additional Comments From jan dot kratochvil at redhat dot com  2010-08-16 17:20 -------
(From update of attachment 4878)
The patch cannot work.


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           What    |Removed                     |Added
----------------------------------------------------------------------------
Attachment #4878 is|0                           |1
           obsolete|                            |


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------- Additional Comments From jan dot kratochvil at redhat dot com  2010-07-10 21:15 -------
Created an attachment (id=4878)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4878&action=view)
gcore reader fix; maybe not needed.


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