[Bug gdb/13987] New: jit debug interface fails attaching to pie executables

[Bug gdb/13987] New: jit debug interface fails attaching to pie executables

[rth at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

             Bug #: 13987
           Summary: jit debug interface fails attaching to pie executables
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
        AssignedTo: unassigned@sourceware.org
        ReportedBy: rth@gcc.gnu.org
    Classification: Unclassified


It appears that when we *attach* to a pie executable, the jit load happens
before the symbols are relocated to the actual pie base address.

Test case is mainline qemu.  Run x86_64-softmmu/qemu-system-x86_64 without
arguments (a window will open booting the bios).  Three scenarios:

(1) Attach gdb to running process:

Attaching to process 28585
jit_inferior_init
Reading symbols from
/home/rth/work/qemu/bld/x86_64-softmmu/qemu-system-x86_64...done.
jit_inferior_init
jit_inferior_init, descriptor_addr = 0x637580
Unable to read JIT descriptor from remote memory!
(gdb) bt
#0  0x00007ff8df1c3403 in ?? ()
#1  0x0000000000000000 in ?? ()


(2) Running qemu directly under gdb:

GNU gdb (GDB) Fedora (7.3.50.20110722-13.fc16)
...
jit_inferior_init
Reading symbols from
/home/rth/work/qemu/bld/x86_64-softmmu/qemu-system-x86_64...done.
jit_inferior_init
jit_inferior_init, descriptor_addr = 0x637580
jit_breakpoint_re_set_internal, breakpoint_addr = 0x237290
(gdb) run
Starting program: /home/rth/work/qemu/bld/x86_64-softmmu/qemu-system-x86_64 
jit_inferior_init
jit_inferior_init
jit_inferior_init, descriptor_addr = 0x555555b8b580
jit_breakpoint_re_set_internal, breakpoint_addr = 0x55555578b290
jit_inferior_init, descriptor_addr = 0x555555b8b580
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
jit_register_code, symfile_addr = 0x555556439f70, symfile_size = 848
[New Thread 0x7fffef088700 (LWP 28666)]
[New Thread 0x7fffe6585700 (LWP 28667)]

Program received signal SIG38, Real-time event 38.
[Switching to Thread 0x7fffef088700 (LWP 28666)]
tlb_set_page (env=0x5555564415b0, vaddr=946176, paddr=946176, prot=7,
mmu_idx=0, size=<optimized out>) at /home/rth/work/qemu/qemu/exec.c:2223
2223        if (is_ram_rom(section)) {
Missing separate debuginfos, use: debuginfo-install
celt051-0.5.1.3-3.fc15.x86_64 libgcc-4.6.3-2.fc16.x86_64
spice-server-0.10.1-1.fc16.x86_64
(gdb) bt
#0  tlb_set_page (env=0x5555564415b0, vaddr=946176, paddr=946176, prot=7,
mmu_idx=0, size=<optimized out>)
    at /home/rth/work/qemu/qemu/exec.c:2223
#1  0x0000555555730264 in cpu_x86_handle_mmu_fault (env=0x5555564415b0,
addr=<optimized out>, is_write1=1, mmu_idx=0)
    at /home/rth/work/qemu/qemu/target-i386/helper.c:762
#2  0x0000555555762ebc in tlb_fill (env1=<optimized out>, addr=<optimized out>,
is_write=<optimized out>, mmu_idx=<optimized out>, retaddr=
    1073754945) at /home/rth/work/qemu/qemu/target-i386/op_helper.c:5015
#3  0x0000555555768b5c in __stb_mmu (addr=949231, val=137 '\211', mmu_idx=0) at
/home/rth/work/qemu/qemu/softmmu_template.h:305
#4  0x0000000040003342 in code_gen_buffer ()
#5  0x000055555570dce1 in cpu_x86_exec (env=0x5555564415b0) at
/home/rth/work/qemu/qemu/cpu-exec.c:565
#6  0x00005555557123ab in tcg_cpu_exec (env=0x5555564415b0) at
/home/rth/work/qemu/qemu/cpus.c:1097
#7  tcg_exec_all () at /home/rth/work/qemu/qemu/cpus.c:1129
#8  qemu_tcg_cpu_thread_fn (arg=<optimized out>) at
/home/rth/work/qemu/qemu/cpus.c:833
#9  0x00007ffff60bad90 in start_thread (arg=0x7fffef088700) at
pthread_create.c:309
#10 0x00007ffff5119f5d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115


(3) Rebuild qemu with --disable-pie and attach to running process:


Attaching to process 28679
Reading symbols from
/home/rth/work/qemu/bld/x86_64-softmmu/qemu-system-x86_64...done.
...
Loaded symbols for /usr/lib64/libXfixes.so.3
jit_inferior_init
jit_inferior_init
jit_inferior_init, descriptor_addr = 0x9e5580
jit_breakpoint_re_set_internal, breakpoint_addr = 0x5e50b0
jit_inferior_init, descriptor_addr = 0x9e5580
0x0000003ef82ea403 in select () at ../sysdeps/unix/syscall-template.S:82
82    T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
(gdb) bt 
#0  0x0000003ef82ea403 in select () at ../sysdeps/unix/syscall-template.S:82
#1  0x0000000000548ee1 in os_host_main_loop_wait (timeout=1000) at
/home/rth/work/qemu/qemu/main-loop.c:304
#2  0x000000000054903b in main_loop_wait (nonblocking=0) at
/home/rth/work/qemu/qemu/main-loop.c:486
#3  0x000000000053bfdb in main_loop () at /home/rth/work/qemu/qemu/vl.c:1555
#4  0x0000000000542b10 in main (argc=1, argv=0x7fff2a711448,
envp=0x7fff2a711458) at /home/rth/work/qemu/qemu/vl.c:3643


Note that in case (2) we re-init the jit inferior again after the program
starts at its actual address, whereas in case (1) we use the unrelocated
symbol address, which then (apparently) causes the rest of symbol resolution
to fail as well.

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[rth at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Richard Henderson <rth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |avi at redhat dot com

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[rth at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Richard Henderson <rth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at redhat dot com

--- Comment #1 from Richard Henderson <rth at gcc dot gnu.org> 2012-04-18 19:16:41 UTC ---
Some poking about suggests that it's too aggressive caching inside jit.c.
The test


jit_breakpoint_re_set_internal (struct gdbarch *gdbarch,
                                struct jit_inferior_data *inf_data)
{
  struct minimal_symbol *reg_symbol, *desc_symbol;
  struct objfile *objf;
  struct jit_objfile_data *objf_data;

  if (inf_data->objfile != NULL)
    return 0;


triggers and fails to re-examine the symbol after
svr4_relocate_main_executable.

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

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

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

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sergiodj at redhat dot com

--- Comment #2 from Tom Tromey <tromey at redhat dot com> 2012-09-17 18:37:46 UTC ---
*** Bug 14585 has been marked as a duplicate of this bug. ***

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at sourceware    |tromey at redhat dot com
                   |dot org                     |

--- Comment #3 from Tom Tromey <tromey at redhat dot com> 2012-09-17 18:40:57 UTC ---
Testing a patch.

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[ppluzhnikov at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppluzhnikov at google dot
                   |                            |com

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[ppluzhnikov at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

--- Comment #4 from Paul Pluzhnikov <ppluzhnikov at google dot com> 2012-10-13 03:21:57 UTC ---
Just hit this while debugging native process from the start:

cat t.c
void __jit_debug_register_code() { }
int __jit_debug_descriptor[] = { 1, 0, 0, 0, };
int main() { return 0; }

gcc -g -fPIE -pie t.c

gdb
GNU gdb (GDB) 7.5.50.20121013-cvs
...
(gdb) set debug jit 1
(gdb) file ./a.out
Reading symbols from /tmp/a.out...done.
jit_inferior_init
jit_read_descriptor, descriptor_addr = 0x201020
jit_breakpoint_re_set_internal, breakpoint_addr = 0x72c
(gdb) run
Starting program: /tmp/a.out 
Warning:
Cannot insert breakpoint -1.
Error accessing memory address 0x72c: Input/output error.

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[ppluzhnikov at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

--- Comment #5 from Paul Pluzhnikov <ppluzhnikov at google dot com> 2012-10-13 03:52:44 UTC ---
Confirmed that this patch:
  http://sourceware.org/ml/gdb-patches/2012-09/msg00320.html
fixes the problem for me, and does not re-introduce the JIT
slowness that caching was solving.

Tom, any chance you can commit the patch?

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[sergiodj at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

--- Comment #6 from Sergio Durigan Junior <sergiodj at redhat dot com> 2012-10-13 04:35:00 UTC ---
(In reply to comment #5)
> Confirmed that this patch:
>   http://sourceware.org/ml/gdb-patches/2012-09/msg00320.html
> fixes the problem for me, and does not re-introduce the JIT
> slowness that caching was solving.
> 
> Tom, any chance you can commit the patch?

Thanks for testing and confirming it.  I have also confirmed that the patch
fixes the issue.

Tom is absent for some days due to personal reasons, but I believe when he gets
back the patch will be pushed upstream.  There is also the possibility of
asking some maintainer to approve the patch and commit it.

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[catalinp at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Catalin Patulea <catalinp at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |catalinp at google dot com

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[cvs-commit at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

--- Comment #7 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> 2013-01-31 19:52:08 UTC ---
CVSROOT:    /cvs/src
Module name:    src
Changes by:    tromey@sourceware.org    2013-01-31 19:52:03

Modified files:
    gdb            : ChangeLog jit.c 
    gdb/testsuite  : ChangeLog 
    gdb/testsuite/gdb.base: jit.exp 

Log message:
    PR gdb/13987:
    * jit.c (struct jit_inferior_data) <cached_code_address,
    jit_breakpoint>: New fields.
    (jit_breakpoint_re_set_internal): Fix logging.  Only create
    breakpoint if cached address has changed.
    (jit_update_inferior_cache, jit_breakpoint_deleted): New
    functions.
    (_initialize_jit): Register breakpoint deleted observer.
    gdb/testsuite
    * gdb.base/jit.exp (compile_jit_test): New proc.
    Add PIE tests.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&r1=1.15092&r2=1.15093
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/jit.c.diff?cvsroot=src&r1=1.46&r2=1.47
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/ChangeLog.diff?cvsroot=src&r1=1.3539&r2=1.3540
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/testsuite/gdb.base/jit.exp.diff?cvsroot=src&r1=1.10&r2=1.11

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[Bug gdb/13987] jit debug interface fails attaching to pie executables

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13987

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |7.6

--- Comment #8 from Tom Tromey <tromey at redhat dot com> 2013-01-31 19:54:26 UTC ---
Fix finally in.

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