[Bug breakpoints/9723] New: gdb core dumps on adding a breakpoint

[Bug breakpoints/9723] New: gdb core dumps on adding a breakpoint

[vaurora at redhat dot com]

I tried to add a breakpoint at function entry.  Oddly, gdb believed that the
breakpoint didn't exist, asking if it should be added pending shared library
load.  I replied yes and started running the program.  When it hit the
breakpoint it core dumped.

Exact version: Fedora (6.8-29.fc10)

The binary I was debugging is available here:

http://valhenson.org/patches/automount

Exact commands to trigger bug:

set args -dfv
break become_daemon (answer y)
run

-- 
           Summary: gdb core dumps on adding a breakpoint
           Product: gdb
           Version: 6.8
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: breakpoints
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: vaurora at redhat dot com
                CC: gdb-prs at sourceware dot org
  GCC host triplet: Fedora 10 x86_64
GCC target triplet: Fedora 10 x86_64


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

------- Additional Comments From pedro at codesourcery dot com  2009-01-09 18:01 -------
Subject: Re:  New: gdb core dumps on adding a breakpoint

On Friday 09 January 2009 17:55:37, vaurora at redhat dot com wrote:
> I tried to add a breakpoint at function entry.  Oddly, gdb believed that the
> breakpoint didn't exist, asking if it should be added pending shared library
> load.  I replied yes and started running the program.  When it hit the
> breakpoint it core dumped.
> 
> Exact version: Fedora (6.8-29.fc10)

Is this happening with FSF gdb as well, or just in redhat's
custom gdb?  If yes, then could you try it with mainline please to check if
it has already been fixed?



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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[vaurora at redhat dot com]

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------- Additional Comments From vaurora at redhat dot com  2009-01-09 20:00 -------
I can't get the gdb-6.8.50.20090109 snapshot to compile:

[val@clunky gdb-6.8.50.20090109]$ ./configure --prefix=/usr/local
[val@clunky gdb-6.8.50.20090109]$ make
[...]
gcc -g -O2   -I. -I.././gdb -I.././gdb/config
-DLOCALEDIR="\"/usr/local/share/locale\"" -DHAVE_CONFIG_H
-I.././gdb/../include/opcode -I.././gdb/../readline/.. -I../bfd
-I.././gdb/../bfd -I.././gdb/../include -I../libdecnumber
-I.././gdb/../libdecnumber  -I.././gdb/gnulib -Ignulib  -DMI_OUT=1 -DTUI=1  
-Wall -Wdeclaration-after-statement -Wpointer-arith -Wformat-nonliteral
-Wno-pointer-sign -Wno-unused -Wno-switch -Wno-char-subscripts -Werror -c -o
coff-pe-read.o -MT coff-pe-read.o -MMD -MP -MF .deps/coff-pe-read.Tpo coff-pe-read.c
coff-pe-read.c: In function ‘read_pe_exported_syms’:
coff-pe-read.c:226: error: expected ‘)’ before ‘;’ token
coff-pe-read.c:358: error: expected ‘;’ before ‘}’ token

If you can install the Fedora gdb rpm, you ought to have all the data necessary
to reproduce it - core file and exact command sequence are included in the
original report.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
     Ever Confirmed|                            |1


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

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------- Additional Comments From pedro at codesourcery dot com  2009-01-09 20:48 -------
Subject: Re:  gdb core dumps on adding a breakpoint

On Friday 09 January 2009 20:00:30, vaurora at redhat dot com wrote:
> 
> ------- Additional Comments From vaurora at redhat dot com  2009-01-09 20:00 -------
> I can't get the gdb-6.8.50.20090109 snapshot to compile:
> 
> [val@clunky gdb-6.8.50.20090109]$ ./configure --prefix=/usr/local
> [val@clunky gdb-6.8.50.20090109]$ make
> [...]
> gcc -g -O2   -I. -I.././gdb -I.././gdb/config
> -DLOCALEDIR="\"/usr/local/share/locale\"" -DHAVE_CONFIG_H
> -I.././gdb/../include/opcode -I.././gdb/../readline/.. -I../bfd
> -I.././gdb/../bfd -I.././gdb/../include -I../libdecnumber
> -I.././gdb/../libdecnumber  -I.././gdb/gnulib -Ignulib  -DMI_OUT=1 -DTUI=1  
> -Wall -Wdeclaration-after-statement -Wpointer-arith -Wformat-nonliteral
> -Wno-pointer-sign -Wno-unused -Wno-switch -Wno-char-subscripts -Werror -c -o
> coff-pe-read.o -MT coff-pe-read.o -MMD -MP -MF .deps/coff-pe-read.Tpo coff-pe-read.c
> coff-pe-read.c: In function ‘read_pe_exported_syms’:
> coff-pe-read.c:226: error: expected ‘)’ before ‘;’ token
> coff-pe-read.c:358: error: expected ‘;’ before ‘}’ token
> 

Oh, chucks, that made it to the last snapshot.  Build errors are rare though.  That's
been fixed in mainline already.  You could try the version before that one, or
wait for a new snapshot, or just try vanilla gdb 6.8.

> If you can install the Fedora gdb rpm, you ought to have all the data necessary
> to reproduce it - core file and exact command sequence are included in the
> original report.

Right, but I also know that your employer has a several local changes in their
tree, over which we're not responsible for.  If you can help with the triage, it
makes it much easier, and the end result being that you get a fixed gdb faster.



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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

------- Additional Comments From pedro at codesourcery dot com  2009-01-12 19:26 -------
Subject: Re:  gdb core dumps on adding a breakpoint

FWI, I've just tried this on:

 - gdb 6.8-debian: 

  Got it to crash as:

(gdb) set args -dfv
(gdb) break become_daemon
Function "become_daemon" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (become_daemon) pending.
(gdb) run
Starting program: /home/pedro/downloads/automount -dfv

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f6cfc0066e0 (LWP 30766)]
0x00000000004a7d4d in disable_breakpoints_at_startup ()

(gdb) bt
#0  0x00000000004a7d4d in disable_breakpoints_at_startup ()
#1  0x00000000004dce6f in post_create_inferior ()
#2  0x00000000004dd274 in ?? ()
#3  0x000000000044d7e2 in execute_command ()
#4  0x00000000004ee04b in ?? ()
#5  0x00000000004eecdb in ?? ()
#6  0x00007f6cfbbf6ea7 in rl_callback_read_char () from /lib/libreadline.so.5
#7  0x00000000004ee229 in ?? ()
#8  0x00000000004eccd3 in ?? ()
#9  0x00000000004ed5e8 in gdb_do_one_event ()
#10 0x00000000004ea4ab in catch_errors ()
#11 0x0000000000493876 in ?? ()
#12 0x0000000000445dc9 in ?? ()
#13 0x00000000004ea4ab in catch_errors ()
#14 0x0000000000446566 in ?? ()
#15 0x00000000004ea4ab in catch_errors ()
#16 0x0000000000445db4 in gdb_main ()
#17 0x0000000000445d86 in main ()

Now, disable_breakpoints_at_startup isn't a function that's in mainline.  This is
part of a series that adds support for PIE.  I know that there are two different
implementations that add PIE support for GDB, one from redhat, and one
from suse.  Maybe debian has the redhat version, and I'm triggering
the same bug you are.

 - vanilla FSF gdb 6.8 

(gdb) run
Starting program: /home/pedro/downloads/automount -dfv
/home/pedro/downloads/automount: this program must be run by root.

Program exited with code 01.
(gdb)   

Ok, so ...

> sudo gdb ...

(gdb) set args -dfv
(gdb) break become_daemon
Function "become_daemon" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (become_daemon) pending.
(gdb) run
Starting program: /home/pedro/downloads/automount -dfv
/home/pedro/downloads/automount: test mount forbidden or incorrect kernel protocol version, kernel protocol version 5.00 or above required.

Program exited with code 01.
(gdb)

 - mainline:

  behaved the same as FSF 6.8.

I've done my best to try to reproduce this.

Can you please confirm if this happens to you with an FSF gdb?  If so, please
provide a backtrace.  Ideally, we'd get a smaller testcase, as I'm not sure
I'm seeing what you're seeing.

I'm reserving the right to close this as invalid if I don't hear back
in a week or so.  ;-)



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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

------- Additional Comments From pedro at codesourcery dot com  2009-01-12 21:50 -------
Subject: Re:  gdb core dumps on adding a breakpoint

On Monday 12 January 2009 19:26:38, pedro at codesourcery dot com wrote:
>  - gdb 6.8-debian: 

For the record, this was ubuntu 8.04's gdb on x86_64.  It seems that ubuntu
people install a bunch of additional patches on top of debian's, and forget to
change the version string.



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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[vaurora at redhat dot com]

------- Additional Comments From vaurora at redhat dot com  2009-01-16 21:27 -------
I retried with this version:

GNU gdb (GDB) 6.8.50.20090108

It does not core dump, hurray!  But I'm still having trouble with breakpoints. 
For example:

[val@clunky src]$ sudo /usr/local/bin/gdb ./automount 
GNU gdb (GDB) 6.8.50.20090108
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
(gdb) break main
Breakpoint 1 at 0x8a90: file automount.c, line 1799.
(gdb) run
Starting program: /home/val/src/automount 
Error in re-setting breakpoint 1: Cannot access memory at address 0x8a90
Error in re-setting breakpoint 1: Cannot access memory at address 0x8a90
/home/val/src/automount: program is already running.

Program exited normally.
(gdb) 

(Ignore the "program is already running" line - it is output from automount
itself and is not correct since it's the bug I was debugging.)

On to the original breakpoint, that doesn't behave correctly either:

[restart gdb]
(gdb) break become_daemon
Function "become_daemon" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y

Breakpoint 1 (become_daemon) pending.
(gdb) run
Starting program: /home/val/src/automount 
/home/val/src/automount: program is already running.

Program exited normally.
(gdb)

First, become_daemon() is not part of a shared library.  Second, the breakpoint
isn't triggering - the "program is already running" check is part of the
become_daemon() function.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[drow at sources dot redhat dot com]

------- Additional Comments From drow at sources dot redhat dot com  2009-01-16 22:00 -------
Yes, this is a typical error when you try to use GDB on a PIE binary.  GDB
doesn't support PIEs; the Ubuntu patch which caused your core dump purports to
add PIE support (but has some issues, I guess).


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[Bug breakpoints/9723] gdb core dumps on adding a breakpoint

[pedro at codesourcery dot com]

------- Additional Comments From pedro at codesourcery dot com  2009-01-16 22:42 -------
Indeed:

>file downloads/automount
downloads/automount: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), for
GNU/Linux 2.6.9, not stripped

There's PR 9174, which is exactly about the fact that we don't support PIE yet.

Valerie, your best bets are to either report the crash bug with Red Hat's gdb to
Red Hat, or, relink your app as a normal executable, to be able to use FSF gdb
on it.

Thanks!


*** This bug has been marked as a duplicate of 9174 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


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[Bug breakpoints/9723] gdb breakpoints silently fail on PIE binaries

[vaurora at redhat dot com]

------- Additional Comments From vaurora at redhat dot com  2009-01-17 00:35 -------
So I don't consider myself a beginning computer user and this still feels like a
bug to me.  Forget the crash in vendor-specific code; with vanilla gdb I set a
breakpoint, it appears to succeed, and then, well, it just doesn't work.

Until such time as PIE support is merged, perhaps gdb could print some sort of
informational message or fail the breakpoint or give some indication that the
expected behavior is that the breakpoint will not be triggered.  It would at
least cut down on the number of duplicate bugs filed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|DUPLICATE                   |
            Summary|gdb core dumps on adding a  |gdb breakpoints silently
                   |breakpoint                  |fail on PIE binaries


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[Bug breakpoints/9723] gdb breakpoints silently fail on PIE binaries

[bauermann at sourceware dot org]

------- Additional Comments From bauermann at sourceware dot org  2009-04-04 21:37 -------
FYI, I'd like to have such warning implemented before we release 7.0, so I plan
to work on this in the next few weeks.

Or we can get lucky and someone will push one of the two current patches
floating around which add support for PIE binaries.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bauermann at sourceware dot
                   |                            |org


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[Bug breakpoints/9723] gdb breakpoints silently fail on PIE binaries

[bauermann at sourceware dot org]

------- Additional Comments From bauermann at sourceware dot org  2009-07-27 23:22 -------
Assigning bug to myself.

Just posted first stab at fixing it to gdb-patches@:

http://sourceware.org/ml/gdb-patches/2009-07/msg00664.html

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at sourceware dot|bauermann at sourceware dot
                   |org                         |org
             Status|REOPENED                    |ASSIGNED


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[Bug breakpoints/9723] gdb breakpoints silently fail on PIE binaries

[bauermann at sourceware dot org]

------- Additional Comments From bauermann at sourceware dot org  2009-08-04 20:47 -------
This bug was just resolved by the following commit:

http://sourceware.org/ml/gdb-cvs/2009-08/msg00014.html

A warning message is now shown when GDB detects that it's dealing with a PIE binary.

See bug #9174 for status on proper support for PIE binaries.

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


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