Fix "New Inferior 2" bug with gdb 10-12 #2193

ALTracer commented 2026年02月10日 18:36:32 +01:00 (Migrated from github.com)

Detailed description

• Not a new feature.
• The existing problem is broken debugging with gdb versions 10 through 12 since PR2010, see #2112.
• This PR solves it by expanding RSP halt-responses and thread info from 1 to p1.1 form aka ppid.tid

Tested against single-core targets like AT32F403A and STM32F411 from BMDA/FT2232H and BMP/blackpill-f411ce. AT32IDE shipped with gdb-10 was affected, and in general some Eclipse CDT-based IDE with old release toolchains for arm-none-eabi.
Untested against multi-core targets like RP2.
Please test this on different gdb versions, probably lldb, and multi-hart (e.g. Cortex-A MPCore), as I don't have well-founded confirmation for a fix like this and why p1.1 is better than 1.

Your checklist for this pull request

• I've read the Code of Conduct
• I've read the guidelines for contributing to this repository
• It builds for hardware native (see Building the firmware)
• It builds as BMDA (see Building the BMDA)
• I've tested it to the best of my ability
• My commit messages provide a useful short description of what the commits do

Closing issues

Fixes #2112.

## Detailed description * Not a new feature. * The existing problem is broken debugging with gdb versions 10 through 12 since PR2010, see #2112. * This PR solves it by expanding RSP halt-responses and thread info from `1` to `p1.1` form aka p`pid`.`tid` Tested against single-core targets like AT32F403A and STM32F411 from BMDA/FT2232H and BMP/blackpill-f411ce. AT32IDE shipped with gdb-10 was affected, and in general some Eclipse CDT-based IDE with old release toolchains for arm-none-eabi. Untested against multi-core targets like RP2. Please test this on different gdb versions, probably lldb, and multi-hart (e.g. Cortex-A MPCore), as I don't have well-founded confirmation for a fix like this and why p1.1 is better than 1. ## Your checklist for this pull request * [x] I've read the [Code of Conduct](https://github.com/blackmagic-debug/blackmagic/blob/main/CODE_OF_CONDUCT.md) * [x] I've read the [guidelines for contributing](https://github.com/blackmagic-debug/blackmagic/blob/main/CONTRIBUTING.md) to this repository * [x] It builds for hardware native (see [Building the firmware](https://github.com/blackmagic-debug/blackmagic?tab=readme-ov-file#building-black-magic-debug-firmware)) * [x] It builds as BMDA (see [Building the BMDA](https://github.com/blackmagic-debug/blackmagic?tab=readme-ov-file#building-black-magic-debug-app)) * [x] I've tested it to the best of my ability * [x] My commit messages provide a useful short description of what the commits do ## Closing issues Fixes #2112.

ALTracer commented 2026年02月10日 19:53:29 +01:00 (Migrated from github.com)

GDB 15.1-1ubuntu2 (which I compiled locally) segfaults spectactularly upon trying to attach to second core of RP2040. Do not merge.

(gdb) det
Detaching from program: /home/altracer/flash.hex, Remote target
[remote] Sending packet: $D#44
[remote] Packet received: OK
[Inferior 1 (Remote target) detached]
(gdb) info threads
[remote] Sending packet: $qfThreadInfo#bb
[remote] Packet received: l
No threads.
(gdb) att 2
Attaching to program: /home/altracer/git/flash.hex, Remote target
[remote] Sending packet: $vAttach;2#38
[remote] Packet received: T05thread:p1.1;
[remote] Sending packet: $qC#b4
[remote] Packet received: QCp1.1
Fatal signal: Segmentation Fault
----- Backtrace ----- 
0x513e28 gdb_internal_backtrace_1
 ./gdb/bt-utils.c:121
0x513e28 _Z22gdb_internal_backtracev
 ./gdb/bt-utils.c:167
0x513e28 _Z22gdb_internal_backtracev
 ./gdb/bt-utils.c:153
0x617e00 handle_fatal_signal
 ./gdb/event-top.c:916
0x617fea handle_sigsegv
 ./gdb/event-top.c:989
0x75510be4251f ???
 ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
0x8f7796 _ZNKSt8__detail18_Mod_range_hashingclEmm
 /usr/include/c++/11/bits/hashtable_policy.h:430
0x8f7796 _ZNKSt8__detail15_Hash_code_baseI6ptid_tSt4pairIKS1_P11thread_infoENS_10_Select1stESt4hashIS1_ENS_18_Mod_range_hashingENS_20_Default_ranged_hashELb1EE15_M_bucket_indexEmm
 /usr/include/c++/11/bits/hashtable_policy.h:1233
0x8f7796 _ZNKSt10_HashtableI6ptid_tSt4pairIKS0_P11thread_infoESaIS5_ENSt8__detail10_Select1stESt8equal_toIS0_ESt4hashIS0_ENS7_18_Mod_range_hashingENS7_20_Default_ranged_hashENS7_20_Prime_rehash_policyENS7_17_Hashtable_traitsILb1ELb0ELb1EEEE15_M_bucket_indexEm
 /usr/include/c++/11/bits/hashtable.h:795 
0x8f7796 _ZNSt10_HashtableI6ptid_tSt4pairIKS0_P11thread_infoESaIS5_ENSt8__detail10_Select1stESt8equal_toIS0_ESt4hashIS0_ENS7_18_Mod_range_hashingENS7_20_Default_ranged_hashENS7_20_Prime_rehash_policyENS7_17_Hashtable_traitsILb1ELb0ELb1EEEE4findERS2_
 /usr/include/c++/11/bits/hashtable.h:1594
0x8f7796 _ZNSt13unordered_mapI6ptid_tP11thread_infoSt4hashIS0_ESt8equal_toIS0_ESaISt4pairIKS0_S2_EEE4findERS8_
 /usr/include/c++/11/bits/unordered_map.h:869
0x8f7796 _ZN8inferior11find_threadE6ptid_t
 ./gdb/inferior.c:251
0x8f7796 _Z17add_thread_silentP22process_stratum_target6ptid_t
 ./gdb/thread.c:310
0x7ed854 _ZN13remote_target17remote_add_threadE6ptid_tbbb
 ./gdb/remote.c:2905
0x7f2cb0 _ZN22extended_remote_target6attachEPKci
 ./gdb/remote.c:6647
0x6963d4 _Z14attach_commandPKci
 ./gdb/infcmd.c:2643
0x54ca84 _Z8cmd_funcP16cmd_list_elementPKci
 ./gdb/cli/cli-decode.c:2741
0x905f00 _Z15execute_commandPKci
 ./gdb/top.c:569
0x61daff _Z15command_handlerPKc
 ./gdb/event-top.c:579
0x61dba1 _Z20command_line_handlerOSt10unique_ptrIcN3gdb13xfree_deleterIcEEE
 ./gdb/event-top.c:815
0x617984 gdb_rl_callback_handler
 ./gdb/event-top.c:271
0x75510d32ce0d ???
0x61cdaa gdb_rl_callback_read_char_wrapper_noexcept
 ./gdb/event-top.c:196
0x61cf90 gdb_rl_callback_read_char_wrapper
 ./gdb/event-top.c:235
0x933d5f stdin_event_handler
 ./gdb/ui.c:154
0xb7837d gdb_wait_for_event
 ../gdbsupport/./gdbsupport/event-loop.cc:672
0xb7837d gdb_wait_for_event
 ../gdbsupport/./gdbsupport/event-loop.cc:563
0xbea60f _Z16gdb_do_one_eventi.constprop.0
 ../gdbsupport/./gdbsupport/event-loop.cc:263
0x6f6c64 start_event_loop
 ./gdb/main.c:400
0x6f6c64 captured_command_loop
 ./gdb/main.c:464
0x448534 captured_main
 ./gdb/main.c:1337
0x448534 _Z8gdb_mainP18captured_main_args
 ./gdb/main.c:1356
0x448534 main
 ./gdb/gdb.c:38
---------------------
A fatal error internal to GDB has been detected, further
debugging is not possible. GDB will now terminate.
This is a bug, please report it. For instructions, see:
<https://www.gnu.org/software/gdb/bugs/>.

Compare to BMDA on main:

(gdb) att 2
Attaching to program: /home/altracer/flash.hex, Remote target
[remote] Sending packet: $vAttach;2#38
[remote] Packet received: T05thread:1;
[remote] packet_ok: Packet vAttach (attach) is supported
[remote] Sending packet: $qC#b4
[remote] Packet received: QC1
[remote] Sending packet: $Hg1#e0
[remote] Packet received: OK
[remote] Sending packet: $qXfer:features:read:target.xml:0,3fb#46
...
[remote] Sending packet: $qXfer:features:read:target.xml:455,3fb#b4
[remote] Packet received: l
[remote] wait: enter
[remote] wait: exit
[remote] Sending packet: $g#67
[remote] Packet received: 0A00000002000000FFFFFFFFFFFFFFFF000000D0800100008101000000ED00E0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF001F04205D0100008401000000000001001F0420FCFFFFFF00000000
[remote] Sending packet: $qfThreadInfo#bb
[remote] Packet received: m1
[remote] Sending packet: $qsThreadInfo#c8
[remote] Packet received: l
[remote] Sending packet: $qXfer:memory-map:read::0,3fb#e5
[remote] Packet received: m<memory-map><memory type="ram" start="0x20000000" length="0x42000"/><memory type="flash" start="0x10000000" length="0x1000000"><property name="blocksize">0x1000</property></memory></memory-map>
[remote] Sending packet: $qXfer:memory-map:read::c1,3fb#49
[remote] Packet received: l

I don't think reporting thread-id 1 for core 2 is perfect, but reporting pid 1 probably crashes gdb, should be pid 2 thread 1?

GDB 15.1-1ubuntu2 (which I compiled locally) segfaults spectactularly upon trying to attach to second core of RP2040. Do not merge. ``` (gdb) det Detaching from program: /home/altracer/flash.hex, Remote target [remote] Sending packet: $D#44 [remote] Packet received: OK [Inferior 1 (Remote target) detached] (gdb) info threads [remote] Sending packet: $qfThreadInfo#bb [remote] Packet received: l No threads. (gdb) att 2 Attaching to program: /home/altracer/git/flash.hex, Remote target [remote] Sending packet: $vAttach;2#38 [remote] Packet received: T05thread:p1.1; [remote] Sending packet: $qC#b4 [remote] Packet received: QCp1.1 Fatal signal: Segmentation Fault ----- Backtrace ----- 0x513e28 gdb_internal_backtrace_1 ./gdb/bt-utils.c:121 0x513e28 _Z22gdb_internal_backtracev ./gdb/bt-utils.c:167 0x513e28 _Z22gdb_internal_backtracev ./gdb/bt-utils.c:153 0x617e00 handle_fatal_signal ./gdb/event-top.c:916 0x617fea handle_sigsegv ./gdb/event-top.c:989 0x75510be4251f ??? ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0 0x8f7796 _ZNKSt8__detail18_Mod_range_hashingclEmm /usr/include/c++/11/bits/hashtable_policy.h:430 0x8f7796 _ZNKSt8__detail15_Hash_code_baseI6ptid_tSt4pairIKS1_P11thread_infoENS_10_Select1stESt4hashIS1_ENS_18_Mod_range_hashingENS_20_Default_ranged_hashELb1EE15_M_bucket_indexEmm /usr/include/c++/11/bits/hashtable_policy.h:1233 0x8f7796 _ZNKSt10_HashtableI6ptid_tSt4pairIKS0_P11thread_infoESaIS5_ENSt8__detail10_Select1stESt8equal_toIS0_ESt4hashIS0_ENS7_18_Mod_range_hashingENS7_20_Default_ranged_hashENS7_20_Prime_rehash_policyENS7_17_Hashtable_traitsILb1ELb0ELb1EEEE15_M_bucket_indexEm /usr/include/c++/11/bits/hashtable.h:795 0x8f7796 _ZNSt10_HashtableI6ptid_tSt4pairIKS0_P11thread_infoESaIS5_ENSt8__detail10_Select1stESt8equal_toIS0_ESt4hashIS0_ENS7_18_Mod_range_hashingENS7_20_Default_ranged_hashENS7_20_Prime_rehash_policyENS7_17_Hashtable_traitsILb1ELb0ELb1EEEE4findERS2_ /usr/include/c++/11/bits/hashtable.h:1594 0x8f7796 _ZNSt13unordered_mapI6ptid_tP11thread_infoSt4hashIS0_ESt8equal_toIS0_ESaISt4pairIKS0_S2_EEE4findERS8_ /usr/include/c++/11/bits/unordered_map.h:869 0x8f7796 _ZN8inferior11find_threadE6ptid_t ./gdb/inferior.c:251 0x8f7796 _Z17add_thread_silentP22process_stratum_target6ptid_t ./gdb/thread.c:310 0x7ed854 _ZN13remote_target17remote_add_threadE6ptid_tbbb ./gdb/remote.c:2905 0x7f2cb0 _ZN22extended_remote_target6attachEPKci ./gdb/remote.c:6647 0x6963d4 _Z14attach_commandPKci ./gdb/infcmd.c:2643 0x54ca84 _Z8cmd_funcP16cmd_list_elementPKci ./gdb/cli/cli-decode.c:2741 0x905f00 _Z15execute_commandPKci ./gdb/top.c:569 0x61daff _Z15command_handlerPKc ./gdb/event-top.c:579 0x61dba1 _Z20command_line_handlerOSt10unique_ptrIcN3gdb13xfree_deleterIcEEE ./gdb/event-top.c:815 0x617984 gdb_rl_callback_handler ./gdb/event-top.c:271 0x75510d32ce0d ??? 0x61cdaa gdb_rl_callback_read_char_wrapper_noexcept ./gdb/event-top.c:196 0x61cf90 gdb_rl_callback_read_char_wrapper ./gdb/event-top.c:235 0x933d5f stdin_event_handler ./gdb/ui.c:154 0xb7837d gdb_wait_for_event ../gdbsupport/./gdbsupport/event-loop.cc:672 0xb7837d gdb_wait_for_event ../gdbsupport/./gdbsupport/event-loop.cc:563 0xbea60f _Z16gdb_do_one_eventi.constprop.0 ../gdbsupport/./gdbsupport/event-loop.cc:263 0x6f6c64 start_event_loop ./gdb/main.c:400 0x6f6c64 captured_command_loop ./gdb/main.c:464 0x448534 captured_main ./gdb/main.c:1337 0x448534 _Z8gdb_mainP18captured_main_args ./gdb/main.c:1356 0x448534 main ./gdb/gdb.c:38 --------------------- A fatal error internal to GDB has been detected, further debugging is not possible. GDB will now terminate. This is a bug, please report it. For instructions, see: <https://www.gnu.org/software/gdb/bugs/>. ``` Compare to BMDA on `main`: ``` (gdb) att 2 Attaching to program: /home/altracer/flash.hex, Remote target [remote] Sending packet: $vAttach;2#38 [remote] Packet received: T05thread:1; [remote] packet_ok: Packet vAttach (attach) is supported [remote] Sending packet: $qC#b4 [remote] Packet received: QC1 [remote] Sending packet: $Hg1#e0 [remote] Packet received: OK [remote] Sending packet: $qXfer:features:read:target.xml:0,3fb#46 ... [remote] Sending packet: $qXfer:features:read:target.xml:455,3fb#b4 [remote] Packet received: l [remote] wait: enter [remote] wait: exit [remote] Sending packet: $g#67 [remote] Packet received: 0A00000002000000FFFFFFFFFFFFFFFF000000D0800100008101000000ED00E0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF001F04205D0100008401000000000001001F0420FCFFFFFF00000000 [remote] Sending packet: $qfThreadInfo#bb [remote] Packet received: m1 [remote] Sending packet: $qsThreadInfo#c8 [remote] Packet received: l [remote] Sending packet: $qXfer:memory-map:read::0,3fb#e5 [remote] Packet received: m<memory-map><memory type="ram" start="0x20000000" length="0x42000"/><memory type="flash" start="0x10000000" length="0x1000000"><property name="blocksize">0x1000</property></memory></memory-map> [remote] Sending packet: $qXfer:memory-map:read::c1,3fb#49 [remote] Packet received: l ``` I don't think reporting thread-id 1 for core 2 is perfect, but reporting pid 1 probably crashes gdb, should be pid 2 thread 1?

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