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From: Lancelot SIX <lsix@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] Fix stepping in rtld without debug symbol Date: Wed, 9 Nov 2022 18:46:25 +0000 (GMT) [thread overview] Message-ID: <20221109184625.AB06A3AA8C25@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=bafcc335266708d5fd62159df90d139d00666ca8 commit bafcc335266708d5fd62159df90d139d00666ca8 Author: Lancelot SIX <lancelot.six@amd.com> Date: Fri Nov 4 15:14:38 2022 +0000 Fix stepping in rtld without debug symbol Commit be6276e0aed "Allow debugging of runtime loader / dynamic linker" introduced a small regression when stepping into the runtime loader / dynamic linker from function we do not have debug information for. This is reported in PR/29747. This can be shown by the following example (given by Simon Marchi in buzilla bug report): $ cat test.c #include <stdio.h> int main() { printf("Hi\n"); return 0; } $ gcc test.c -O0 -o test $ ./gdb -q -nx --data-directory=data-directory test -ex start -ex s Reading symbols from test... (No debugging symbols found in test) Temporary breakpoint 1 at 0x1151 Starting program: .../binutils-gdb/gdb/test [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Temporary breakpoint 1, 0x0000555555555151 in main () Single stepping until exit from function main, which has no line number information. /home/smarchi/src/binutils-gdb/gdb/infrun.c:6960:64: runtime error: member call on null pointer of type 'struct symbol' The crash happens here: #0 __sanitizer::Die () at ../../../../src/libsanitizer/sanitizer_common/sanitizer_termination.cpp:50 #1 0x00007ffff5dd7128 in __ubsan::__ubsan_handle_type_mismatch_v1_abort (Data=<optimized out>, Pointer=<optimized out>) at ../../../../src/libsanitizer/ubsan/ubsan_handlers.cpp:148 #2 0x000055556183e1a7 in process_event_stop_test (ecs=0x7fffffffccd0) at .../binutils-gdb/gdb/infrun.c:6960 #3 0x0000555561838ea4 in handle_signal_stop (ecs=0x7fffffffccd0) at .../binutils-gdb/gdb/infrun.c:6615 #4 0x000055556182f77b in handle_inferior_event (ecs=0x7fffffffccd0) at .../binutils-gdb/gdb/infrun.c:5866 When evaluating: 6956 if (execution_direction != EXEC_REVERSE 6957 && ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE 6958 && in_solib_dynsym_resolve_code (ecs->event_thread->stop_pc ()) 6959 && !in_solib_dynsym_resolve_code ( 6961 ecs->event_thread->control.step_start_function->value_block () 6962 ->entry_pc ())) we dereference, ecs->event_thread->control.step_start_function which is nullptr. This patch changes this condition so it evaluates to true if ecs->event_thread->control.step_start_function is nullptr since this matches the behaviour before be6276e0aed. Tested on ubuntu-22.04 x86_64. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29747 Reviewed-By: Bruno Larsen <blarsen@redhat.com> Approved-By: Kevin Buettner <kevinb@redhat.com> Diff: --- gdb/infrun.c | 7 +++--- gdb/testsuite/gdb.base/rtld-step-nodebugsym.c | 25 +++++++++++++++++++ gdb/testsuite/gdb.base/rtld-step-nodebugsym.exp | 32 +++++++++++++++++++++++++ 3 files changed, 61 insertions(+), 3 deletions(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index 5ff0dc44d03..6da46b75ac7 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -6956,9 +6956,10 @@ process_event_stop_test (struct execution_control_state *ecs) if (execution_direction != EXEC_REVERSE && ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE && in_solib_dynsym_resolve_code (ecs->event_thread->stop_pc ()) - && !in_solib_dynsym_resolve_code ( - ecs->event_thread->control.step_start_function->value_block () - ->entry_pc ())) + && (ecs->event_thread->control.step_start_function == nullptr + || !in_solib_dynsym_resolve_code ( + ecs->event_thread->control.step_start_function->value_block () + ->entry_pc ()))) { CORE_ADDR pc_after_resolver = gdbarch_skip_solib_resolver (gdbarch, ecs->event_thread->stop_pc ()); diff --git a/gdb/testsuite/gdb.base/rtld-step-nodebugsym.c b/gdb/testsuite/gdb.base/rtld-step-nodebugsym.c new file mode 100644 index 00000000000..2e01da65699 --- /dev/null +++ b/gdb/testsuite/gdb.base/rtld-step-nodebugsym.c @@ -0,0 +1,25 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2022 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <stdio.h> + +int +main (void) +{ + printf ("hello world"); + return 0; +} diff --git a/gdb/testsuite/gdb.base/rtld-step-nodebugsym.exp b/gdb/testsuite/gdb.base/rtld-step-nodebugsym.exp new file mode 100644 index 00000000000..1c8fa478cb8 --- /dev/null +++ b/gdb/testsuite/gdb.base/rtld-step-nodebugsym.exp @@ -0,0 +1,32 @@ +# Copyright 2022 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + +# Test stepping through a runtime loader / dynamic linker (RTLD) without +# debug info. + +standard_testfile + +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} \ + {nodebug}] } { + return +} + +if { ![runto_main] } { + return +} + +gdb_test "step" "Single stepping until exit from function.*" + +gdb_continue_to_end "" continue 1
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