ld: Always consider -L args and allow a Gentoo-specific prefix override #6
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This is for consistency with other linkers, including gold. Without this, we typically rely on ld.so.conf to find libraries such as libstdc++.so.6, while other linkers do not use this file at all.
This prefix is only used to locate $prefix/etc/ld.so.conf, with $prefix usually being /usr. This file is important on Gentoo Prefix systems, where the /usr prefix is within another directory. The problem is that Gentoo already passes the same directory as the sysroot, and ld.bfd therefore looks for /myprefix/myprefix/usr/etc/ld.so.conf. The sysroot is dynamic, while the prefix is hardcoded. A hardcoded prefix that isn't just /usr is unhelpful, not just because of the doubled prefix issue above, but also because it prevents ld.bfd from working effectively outside its native environment. We will therefore hardcode it to just /usr. This change does not simply do that though and sets up a $gentoo_prefix variable instead, with $prefix as a fallback. This is necessary because Gentoo prefix-guest systems, which use the host's libc, do not apply a sysroot like RAP prefix systems do. In that case, we must preserve the existing behaviour. The binutils ebuild will be responsible for setting this variable appropriately.
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I've rebased #5 now, so you can close this. Thanks! |
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The commit: commit c6b4867 Date: Thu Mar 30 19:21:22 2023 +0100 gdb: parse pending breakpoint thread/task immediately Introduce a use bug where the value of a temporary variable was being used after it had gone out of scope. This was picked up by the address sanitizer and would result in this error: (gdb) maintenance selftest create_breakpoint_parse_arg_string Running selftest create_breakpoint_parse_arg_string. ================================================================= ==2265825==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fbb08046511 at pc 0x000001632230 bp 0x7fff7c2fb770 sp 0x7fff7c2fb768 READ of size 1 at 0x7fbb08046511 thread T0 #0 0x163222f in create_breakpoint_parse_arg_string(char const*, std::unique_ptr<char, gdb::xfree_deleter<char> >*, int*, int*, int*, std::unique_ptr<char, gdb::xfree_deleter<char> >*, bool*) ../../src/gdb/break-cond-parse.c:496 #1 0x1633026 in test ../../src/gdb/break-cond-parse.c:582 #2 0x163391b in create_breakpoint_parse_arg_string_tests ../../src/gdb/break-cond-parse.c:649 #3 0x12cfebc in void std::__invoke_impl<void, void (*&)()>(std::__invoke_other, void (*&)()) /usr/include/c++/13/bits/invoke.h:61 #4 0x12cc8ee in std::enable_if<is_invocable_r_v<void, void (*&)()>, void>::type std::__invoke_r<void, void (*&)()>(void (*&)()) /usr/include/c++/13/bits/invoke.h:111 #5 0x12c81e5 in std::_Function_handler<void (), void (*)()>::_M_invoke(std::_Any_data const&) /usr/include/c++/13/bits/std_function.h:290 #6 0x18bb51d in std::function<void ()>::operator()() const /usr/include/c++/13/bits/std_function.h:591 #7 0x4193ef9 in selftests::run_tests(gdb::array_view<char const* const>, bool) ../../src/gdbsupport/selftest.cc:100 #8 0x21c2206 in maintenance_selftest ../../src/gdb/maint.c:1172 ... etc ... The problem was caused by three lines like this one: thread_info *thr = parse_thread_id (std::string (t.get_value ()).c_str (), &tmptok); After parsing the thread-id TMPTOK would be left pointing into the temporary string which had been created on this line. When on the next line we did this: gdb_assert (*tmptok == '\0'); The value of *TMPTOK is undefined. Fix this by creating the std::string earlier in the scope. Now the contents of the string will remain valid when we check *TMPTOK. The address sanitizer issue is now resolved.
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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 <[email protected]>
Reviewed-by: Keith Seitz <[email protected]>
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When building gdb with gcc 12 and -fsanitize=threads while renabling
background dwarf reading by setting dwarf_synchronous to false, I run into:
...
(gdb) file amd64-watchpoint-downgrade
Reading symbols from amd64-watchpoint-downgrade...
(gdb) watch global_var
==================
WARNING: ThreadSanitizer: data race (pid=20124)
Read of size 8 at 0x7b80000500d8 by main thread:
#0 cooked_index_entry::full_name(obstack*, bool) const cooked-index.c:220
#1 cooked_index::get_main_name(obstack*, language*) const cooked-index.c:735
#2 cooked_index_worker::wait(cooked_state, bool) cooked-index.c:559
#3 cooked_index::wait(cooked_state, bool) cooked-index.c:631
#4 cooked_index_functions::wait(objfile*, bool) cooked-index.h:729
#5 cooked_index_functions::compute_main_name(objfile*) cooked-index.h:806
#6 objfile::compute_main_name() symfile-debug.c:461
#7 find_main_name symtab.c:6503
#8 main_language() symtab.c:6608
#9 set_initial_language_callback symfile.c:1634
#10 get_current_language() language.c:96
...
Previous write of size 8 at 0x7b80000500d8 by thread T1:
#0 cooked_index_shard::finalize(parent_map_map const*) \
dwarf2/cooked-index.c:409
#1 operator() cooked-index.c:663
...
...
SUMMARY: ThreadSanitizer: data race cooked-index.c:220 in \
cooked_index_entry::full_name(obstack*, bool) const
==================
Hardware watchpoint 1: global_var
(gdb) PASS: gdb.arch/amd64-watchpoint-downgrade.exp: watch global_var
...
This was also reported in PR31715.
This is due do gcc PR110799 [1], generating wrong code with
-fhoist-adjacent-loads, and causing a false positive for
-fsanitize=threads.
Work around the gcc PR by forcing -fno-hoist-adjacent-loads for gcc <= 13
and -fsanitize=threads.
Tested in that same configuration on x86_64-linux. Remaining ThreadSanitizer
problems are the ones reported in PR31626 (gdb.rust/dwindex.exp) and
PR32247 (gdb.trace/basic-libipa.exp).
PR gdb/31715
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31715
Tested-By: Bernd Edlinger <[email protected]>
Approved-By: Tom Tromey <[email protected]>
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110799
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When calling a function with double arguments, I get this asan error:
==7920==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x0053131ece38 at pc 0x7ff79697a68f bp 0x0053131ec790 sp 0x0053131ebf40
READ of size 16 at 0x0053131ece38 thread T0
#0 0x7ff79697a68e in MemcmpInterceptorCommon(void*, int (*)(void const*, void const*, unsigned long long), void const*, void const*, unsigned long long) C:/gcc/src/gcc-14.2.0/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:814
#1 0x7ff79697aebd in memcmp C:/gcc/src/gcc-14.2.0/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:845
#2 0x7ff79697aebd in memcmp C:/gcc/src/gcc-14.2.0/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:840
#3 0x7ff7927e237f in regcache::raw_write(int, gdb::array_view<unsigned char const>) C:/gdb/src/gdb.git/gdb/regcache.c:874
#4 0x7ff7927e3c85 in regcache::cooked_write(int, gdb::array_view<unsigned char const>) C:/gdb/src/gdb.git/gdb/regcache.c:914
#5 0x7ff7927e5d89 in regcache::cooked_write(int, unsigned char const*) C:/gdb/src/gdb.git/gdb/regcache.c:933
#6 0x7ff7911d5965 in amd64_windows_store_arg_in_reg C:/gdb/src/gdb.git/gdb/amd64-windows-tdep.c:216
Address 0x0053131ece38 is located in stack of thread T0 at offset 40 in frame
#0 0x7ff7911d565f in amd64_windows_store_arg_in_reg C:/gdb/src/gdb.git/gdb/amd64-windows-tdep.c:208
This frame has 4 object(s):
[32, 40) 'buf' (line 211) <== Memory access at offset 40 overflows this variable
It's because the first 4 double arguments are passed via XMM registers,
and they need a buffer of 16 bytes, even if we only use 8 bytes of them.
Approved-By: Tom Tromey <[email protected]>
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On Windows gcore is not implemented, and if you try it, you get an
heap-use-after-free error:
(gdb) gcore C:/gdb/build64/gdb-git-python3/gdb/testsuite/outputs/gdb.base/gcore-buffer-overflow/gcore-buffer-overflow.test
warning: cannot close "=================================================================
==10108==ERROR: AddressSanitizer: heap-use-after-free on address 0x1259ea503110 at pc 0x7ff6806e3936 bp 0x0062e01ed990 sp 0x0062e01ed140
READ of size 111 at 0x1259ea503110 thread T0
#0 0x7ff6806e3935 in strlen C:/gcc/src/gcc-14.2.0/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:391
#1 0x7ff6807169c4 in __pformat_puts C:/gcc/src/mingw-w64-v12.0.0/mingw-w64-crt/stdio/mingw_pformat.c:558
#2 0x7ff6807186c1 in __mingw_pformat C:/gcc/src/mingw-w64-v12.0.0/mingw-w64-crt/stdio/mingw_pformat.c:2514
#3 0x7ff680713614 in __mingw_vsnprintf C:/gcc/src/mingw-w64-v12.0.0/mingw-w64-crt/stdio/mingw_vsnprintf.c:41
#4 0x7ff67f34419f in vsnprintf(char*, unsigned long long, char const*, char*) C:/msys64/mingw64/x86_64-w64-mingw32/include/stdio.h:484
#5 0x7ff67f34419f in string_vprintf[abi:cxx11](char const*, char*) C:/gdb/src/gdb.git/gdbsupport/common-utils.cc:106
#6 0x7ff67b37b739 in cli_ui_out::do_message(ui_file_style const&, char const*, char*) C:/gdb/src/gdb.git/gdb/cli-out.c:227
#7 0x7ff67ce3d030 in ui_out::call_do_message(ui_file_style const&, char const*, ...) C:/gdb/src/gdb.git/gdb/ui-out.c:571
#8 0x7ff67ce4255a in ui_out::vmessage(ui_file_style const&, char const*, char*) C:/gdb/src/gdb.git/gdb/ui-out.c:740
#9 0x7ff67ce2c873 in ui_file::vprintf(char const*, char*) C:/gdb/src/gdb.git/gdb/ui-file.c:73
#10 0x7ff67ce7f83d in gdb_vprintf(ui_file*, char const*, char*) C:/gdb/src/gdb.git/gdb/utils.c:1881
#11 0x7ff67ce7f83d in vwarning(char const*, char*) C:/gdb/src/gdb.git/gdb/utils.c:181
#12 0x7ff67f3530eb in warning(char const*, ...) C:/gdb/src/gdb.git/gdbsupport/errors.cc:33
#13 0x7ff67baed27f in gdb_bfd_close_warning C:/gdb/src/gdb.git/gdb/gdb_bfd.c:437
#14 0x7ff67baed27f in gdb_bfd_close_or_warn C:/gdb/src/gdb.git/gdb/gdb_bfd.c:646
#15 0x7ff67baed27f in gdb_bfd_unref(bfd*) C:/gdb/src/gdb.git/gdb/gdb_bfd.c:739
#16 0x7ff68094b6f2 in gdb_bfd_ref_policy::decref(bfd*) C:/gdb/src/gdb.git/gdb/gdb_bfd.h:82
#17 0x7ff68094b6f2 in gdb::ref_ptr<bfd, gdb_bfd_ref_policy>::~ref_ptr() C:/gdb/src/gdb.git/gdbsupport/gdb_ref_ptr.h:91
#18 0x7ff67badf4d2 in gcore_command C:/gdb/src/gdb.git/gdb/gcore.c:176
0x1259ea503110 is located 16 bytes inside of 4064-byte region [0x1259ea503100,0x1259ea5040e0)
freed by thread T0 here:
#0 0x7ff6806b1687 in free C:/gcc/src/gcc-14.2.0/libsanitizer/asan/asan_malloc_win.cpp:90
#1 0x7ff67f2ae807 in objalloc_free C:/gdb/src/gdb.git/libiberty/objalloc.c:187
#2 0x7ff67d7f56e3 in _bfd_free_cached_info C:/gdb/src/gdb.git/bfd/opncls.c:247
#3 0x7ff67d7f2782 in _bfd_delete_bfd C:/gdb/src/gdb.git/bfd/opncls.c:180
#4 0x7ff67d7f5df9 in bfd_close_all_done C:/gdb/src/gdb.git/bfd/opncls.c:960
#5 0x7ff67d7f62ec in bfd_close C:/gdb/src/gdb.git/bfd/opncls.c:925
#6 0x7ff67baecd27 in gdb_bfd_close_or_warn C:/gdb/src/gdb.git/gdb/gdb_bfd.c:643
#7 0x7ff67baecd27 in gdb_bfd_unref(bfd*) C:/gdb/src/gdb.git/gdb/gdb_bfd.c:739
#8 0x7ff68094b6f2 in gdb_bfd_ref_policy::decref(bfd*) C:/gdb/src/gdb.git/gdb/gdb_bfd.h:82
#9 0x7ff68094b6f2 in gdb::ref_ptr<bfd, gdb_bfd_ref_policy>::~ref_ptr() C:/gdb/src/gdb.git/gdbsupport/gdb_ref_ptr.h:91
#10 0x7ff67badf4d2 in gcore_command C:/gdb/src/gdb.git/gdb/gcore.c:176
It happens because gdb_bfd_close_or_warn uses a bfd-internal name for
the failing-close warning, after the close is finished, and the name
already freed:
static int
gdb_bfd_close_or_warn (struct bfd *abfd)
{
int ret;
const char *name = bfd_get_filename (abfd);
for (asection *sect : gdb_bfd_sections (abfd))
free_one_bfd_section (sect);
ret = bfd_close (abfd);
if (!ret)
gdb_bfd_close_warning (name,
bfd_errmsg (bfd_get_error ()));
return ret;
}
Fixed by making a copy of the name for the warning.
Approved-By: Andrew Burgess <[email protected]>
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Rebase of #5