tree dff328a9d989b773851e41f3c0af59560631d8a2
parent b8b60e2d0cb0ab1f235f082dbb8a4e8bc43aadf6
author Simon Marchi <simon.marchi@efficios.com> 1726144028 -0400
committer Simon Marchi <simon.marchi@efficios.com> 1726153334 -0400

gdb: change type of `general_symbol_info::m_section` to int

The binary provided with bug 32165 [1] has 36139 ELF sections.  GDB
crashes on it with (note that my GDB is build with -D_GLIBCXX_DEBUG=1:

    $ ./gdb  -nx -q --data-directory=data-directory ./vmlinux
    Reading symbols from ./vmlinux...
    (No debugging symbols found in ./vmlinux)
    (gdb) info func
    /usr/include/c++/14.2.1/debug/vector:508:
    In function:
        std::debug::vector<_Tp, _Allocator>::reference std::debug::vector<_Tp,
        _Allocator>::operator[](size_type) [with _Tp = long unsigned int;
        _Allocator = std::allocator<long unsigned int>; reference = long
        unsigned int&; size_type = long unsigned int]

    Error: attempt to subscript container with out-of-bounds index -29445, but
    container only holds 36110 elements.

    Objects involved in the operation:
        sequence "this" @ 0x514000007340 {
          type = std::debug::vector<unsigned long, std::allocator<unsigned long> >;
        }

The crash occurs here:

    #3  0x00007ffff5e334c3 in __GI_abort () at abort.c:79
    #4  0x00007ffff689afc4 in __gnu_debug::_Error_formatter::_M_error (this=<optimized out>) at /usr/src/debug/gcc/gcc/libstdc++-v3/src/c++11/debug.cc:1320
    #5  0x0000555561119a16 in std::__debug::vector<unsigned long, std::allocator<unsigned long> >::operator[] (this=0x514000007340, __n=18446744073709522171)
        at /usr/include/c++/14.2.1/debug/vector:508
    #6  0x0000555562e288e8 in minimal_symbol::value_address (this=0x5190000bb698, objfile=0x514000007240) at /home/smarchi/src/binutils-gdb/gdb/symtab.c:517
    #7  0x0000555562e5a131 in global_symbol_searcher::expand_symtabs (this=0x7ffff0f5c340, objfile=0x514000007240, preg=std::optional [no contained value])
        at /home/smarchi/src/binutils-gdb/gdb/symtab.c:4983
    #8  0x0000555562e5d2ed in global_symbol_searcher::search (this=0x7ffff0f5c340) at /home/smarchi/src/binutils-gdb/gdb/symtab.c:5189
    #9  0x0000555562e5ffa4 in symtab_symbol_info (quiet=false, exclude_minsyms=false, regexp=0x0, kind=FUNCTION_DOMAIN, t_regexp=0x0, from_tty=1)
        at /home/smarchi/src/binutils-gdb/gdb/symtab.c:5361
    #10 0x0000555562e6131b in info_functions_command (args=0x0, from_tty=1) at /home/smarchi/src/binutils-gdb/gdb/symtab.c:5525

That is, at this line of `minimal_symbol::value_address`, where
`objfile->section_offsets` is an `std::vector`:

    return (CORE_ADDR (this->unrelocated_address ())
	    + objfile->section_offsets[this->section_index ()]);

A section index of -29445 is suspicious.  The minimal_symbol at play
here is:

    (top-gdb) p m_name
    $1 = 0x521001de10af "_sinittext"

So I restarted debugging, breaking on:

   (top-gdb) b general_symbol_info::set_section_index if $_streq("_sinittext", m_name)

And I see that weird -29445 value:

    (top-gdb) frame
    #0  general_symbol_info::set_section_index (this=0x525000082390, idx=-29445) at /home/smarchi/src/binutils-gdb/gdb/symtab.h:611
    611       { m_section = idx; }

But going up one frame, the section index is 36091:

    (top-gdb) frame
    #1  0x0000555562426526 in minimal_symbol_reader::record_full (this=0x7ffff0ead560, name="_sinittext", copy_name=false,
        address=-2111475712, ms_type=mst_text, section=36091) at /home/smarchi/src/binutils-gdb/gdb/minsyms.c:1228
    1228      msymbol->set_section_index (section);

It seems like the problem is just that the type used for the section
index (short) is not big enough.  Change from short to int.  If somebody
insists, we could even go long long / int64_t, but I doubt it's
necessary.

With that fixed, I get:

    (gdb) info func
    All defined functions:

    Non-debugging symbols:
    0xffffffff81000000  _stext
    0xffffffff82257000  _sinittext
    0xffffffff822b4ebb  _einittext

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=32165

Change-Id: Icb1c3de9474ff5adef7e0bbbf5e0b67b279dee04
Reviewed-By: Tom de Vries <tdevries@suse.de>
Reviewed-by: Keith Seitz <keiths@redhat.com>