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9783247189
While looking at build_id_to_bfd_suffix (in gdb/build-id.c) I realised that GDB would likely not do what we wanted if a build-id was ever a single byte. Right now, build-ids generated by the GNU linker are 32 bytes, but there's nothing that forces this to be the case, it's pretty easy to create a fake, single byte, build-id. Given that the build-id is an external input (read from the objfile), GDB should protect itself against these edge cases. The problem with build_id_to_bfd_suffix is that this function creates the path used to lookup either the debug information, or an executable, based on its build-id. So a 3-byte build-id 0xaabbcc will look in the path: `$DEBUG_FILE_DIRECTORY/.build-id/aa/bbcc.debug`. However, a single byte build-id 0xaa, will look in the file: `$DEBUG_FILE_DIRECTORY/.build-id/aa/.debug` which doesn't seem right. Worse, when looking for an objfile given a build-id GDB will look for a file called `$DEBUG_FILE_DIRECTORY/.build-id/aa/` with a trailing '/' character. I propose that, in build_id_to_bfd_suffix we just return early if the build-id is 1 byte (or less) with a return value that indicates no separate file was found. For testing I made use of the DWARF assembler. I needed to update the build-id creation proc, the existing code assumes that the build-id is a multiple of 4 bytes, so I added some additional padding to ensure that the generated note was a multiple of 4 bytes, even if the build-id was not. I added a test with a 1 byte build-id, and also for the case where the build-id has zero length. The zero length case already does what you'd expect (no debug is loaded) as the bfd library rejects the build-id when loading it from the objfile, but adding this additional test is pretty cheap. Approved-By: Kevin Buettner <kevinb@redhat.com>
120 lines
3.7 KiB
Plaintext
120 lines
3.7 KiB
Plaintext
# Copyright 2024 Free Software Foundation, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Create a file with an artificially short (1-byte) build-id, and
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# check that GDB doesn't try to load debug information. If we do try
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# then we end up loading from: `debug-directory/.build-id/xx/.debug`
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# which isn't right.
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-2 and use gas.
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require dwarf2_support
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# No remote host testing either.
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require {!is_remote host}
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standard_testfile main.c
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# Create an assembler file which encodes BUILDID as the build-id. Compile
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# this along with the global SRCFILE to create a test executable.
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#
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# Split the debug information out from the newly created executable and place
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# it into the debug file directory.
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#
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# Load the executable into GDB and check to see if the debug information was
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# loaded or not. For this test we are expecting that the debug information
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# was not loaded. The reason is that, with short values for BUILDID, GDB ends
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# up looking for the debug information in weird locations.
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proc run_test { buildid } {
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set len [string length $buildid]
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set asm_file [standard_output_file "$::testfile.$len.S"]
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Dwarf::assemble $asm_file {
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declare_labels int_label int_label2
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upvar buildid buildid
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build_id $buildid
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cu { label cu_start } {
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compile_unit {{language @DW_LANG_C}} {
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int_label2: base_type {
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{name int}
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{byte_size 4 sdata}
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{encoding @DW_ATE_signed}
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}
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constant {
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{name the_int}
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{type :$int_label2}
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{const_value 99 data1}
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}
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}
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}
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aranges {} cu_start {
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arange {} 0 0
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}
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}
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set execfile [standard_output_file $::testfile.$len]
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if { [build_executable_from_specs "failed to build" \
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$execfile {debug no-build-id} \
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$::srcfile debug \
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$asm_file {}] } {
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return
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}
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# Create the debug directory.
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set debugdir [standard_output_file "debugdir.$len"]
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set build_id_dir $debugdir/.build-id/$buildid
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remote_exec host "mkdir -p $build_id_dir"
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# Split out the debug information.
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if {[gdb_gnu_strip_debug $execfile no-debuglink]} {
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unresolved "failed to split out debug information"
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return
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}
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# Move the debug information into the debug directory. We place the debug
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# information into a file called just '.debug'. GDB should not check this
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# file, but at one point GDB would check this file, even though this
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# doesn't make much sense.
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set execfile_debug ${execfile}.debug
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remote_exec host "mv $execfile_debug $build_id_dir/.debug"
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# Start GDB, set the debug-file-directory, and try loading the file.
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clean_restart
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gdb_test_no_output "set debug-file-directory $debugdir" \
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"set debug-file-directory"
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gdb_file_cmd $execfile
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gdb_assert { $::gdb_file_cmd_debug_info eq "nodebug" } \
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"no debug should be loaded"
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# For sanity, read something that was encoded in the debug
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# information, this should fail.
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gdb_test "print the_int" \
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"(?:No symbol table is loaded|No symbol \"the_int\" in current context).*"
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}
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foreach_with_prefix buildid { a4 "" } {
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run_test $buildid
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}
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