[Bug backtrace/29074] New: gdb fails to find a shared library for a function

[Bug backtrace/29074] New: gdb fails to find a shared library for a function

[rui314 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

            Bug ID: 29074
           Summary: gdb fails to find a shared library for a function
           Product: gdb
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: backtrace
          Assignee: unassigned at sourceware dot org
          Reporter: rui314 at gmail dot com
  Target Milestone: ---

It looks like gdb sometimes fails to find a shared library name for a function.
My shared library ends with something like this:

ruiu@blue:~/mold$ objdump -d liba.so
<<<omit>>>
0000000000001140 <_ZL5func2i>:
    1140:       55                      push   %rbp
    1141:       48 89 e5                mov    %rsp,%rbp
    1144:       48 83 ec 10             sub    $0x10,%rsp
    1148:       89 7d fc                mov    %edi,-0x4(%rbp)
    114b:       e8 c0 fe ff ff          call   1010 <abort@plt>
ruiu@blue:~/mold$

So, the DSO's text segment ends with a call to `abort`. Since GCC knows `abort`
does not return, it can emit code like this.

When gdb tries to lookup a shared library using a function return address as a
key, the "return address" for the above function is one byte beyond the
executable segment of the DSO. Because of that, gdb fails to find a shared
library for that function. An example output is shown below:

Program received signal SIGABRT, Aborted.
0x00007ffff70b0cdb in raise () from /lib64/libc.so.6
(gdb) bt
#0 0x00007ffff70b0cdb in raise () from /lib64/libc.so.6
#1 0x00007ffff70b2375 in abort () from /lib64/libc.so.6
#2 0x00007ffff7ff0140 in func2(int) ()
#3 0x00007ffff7ff0123 in func(int) () from ./liba.so
#4 0x0000000000201149 in main () at a1.cpp:2

The third line from the bottom lacks the shared library name.

I believe gdb has to subtract one byte from a return address before using it to
lookup a shared library.

This is originally reported at https://github.com/rui314/mold/issues/444

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

Tom Tromey <tromey at sourceware dot org> changed:

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

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
Another case of bug#8416.
Easy to fix but I am not sure how to write a robust test.

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=8416,
                   |                            |https://github.com/rui314/m
                   |                            |old/issues/444
                 CC|                            |sam at gentoo dot org

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-08-01
             Status|UNCONFIRMED                 |NEW
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org
     Ever confirmed|0                           |1

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
Perhaps a non-robust test is good enough.

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
https://sourceware.org/pipermail/gdb-patches/2023-August/201370.html

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=9030a82d6f700e03ab143f0d002e9f21ae2fd52f

commit 9030a82d6f700e03ab143f0d002e9f21ae2fd52f
Author: Tom Tromey <tom@tromey.com>
Date:   Tue Aug 1 15:09:49 2023 -0600

    Use get_frame_address_in_block in print_frame

    The author of 'mold' pointed out that with a certain shared library,
    gdb would fail to find the shared library's name in 'bt'.

    The function in question appeared at the end of the .so's .text
    segment and ended with a call to 'abort'.

    This turned out to be a classic case of calling get_frame_pc when
    get_frame_address_in_block is needed -- the former will be off-by-one
    for purposes of finding the enclosing function or shared library.

    The included test fails without the patch on my system.  However, I
    imagine it can't be assumed to reliably fail.  Nevertheless it seemed
    worth doing.

    Regression tested on x86-64 Fedora 38.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29074
    Reviewed-by: Kevin Buettner <kevinb@redhat.com>

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[Bug backtrace/29074] gdb fails to find a shared library for a function

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29074

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |14.1
             Status|NEW                         |RESOLVED

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
Fixed.

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