Ivan Grokhotkov 0adf0f85dd gdbstub: fix thread list generation ... This commit fixes an issue with gdbstub, where it would list threads with TIDs 1 to N in qfThreadInfo/qsThreadInfo responses, and then would tell GDB that the current TID is 0 in the qC response. This caused an assertion failure in GDB, because it couldn't find the thread structure corresponding to TID 0: src/gdb/gdb/thread.c:93: internal-error: thread_info* inferior_thread(): Assertion `tp' failed. The issue was caused by the logic of qfThreadInfo/qsThreadInfo. If the "paniced" task index was 1, the code would report it in the response to qfThreadInfo, and then mistakenly skip task with index 0 in qsThreadInfo, due to the use of pre-increment instead of a post-increment. With that issue fixed, GDB assertion doesn't happen anymore. However the code contained a deeper problem, which manifested itself in the fact that GDB would incorrectly show task index 0 as the current task, after the above fix. Previous version of the code assumed that when GDB requests the thread list, it uses the first thread returned by the target as the "default" thread, and subsequently shows the user that the program is stopped in that thread. This assumption was incorrect. In fact, after connecting to a remote target, GDB obtains information about the "default" or "current" thread from two sources: 1. the 'thread' special register indicated in the status response ($T00thread;00000001#ee) 2. if the target has only sent the plain stop response ($T00#ee), GDB would ask for the current thread using a qC packet. With that in mind, it is not necessary to report the paniced task as the first task in qfThreadInfo response. We can simply returns the tasks in their natural order, and then indicate the current task in the qS packet response. However even that change does not fully resolve the issues with task list. The previous version of this code also incorrectly interpreted the meaning of GDB TIDs -1 and 0. When GDB sends an "Hg0" command early in the connection process, it doesn't expect the server to set task 0 as the current task, as the code assumed. Rather, it tells the server to "set any (arbitrary) task as the current one", and the most logical thing to do for the server that is already in "stopped" state is to keep the current task selection. Since TID 0 has a special meaning in GDB remote protocol, gdbstub code is now modified to map task indices (which start from 0) to GDB TIDs. GDB TIDs are arbitrary, and for simplicity we keep the same order and start counting them from 1. The summary of all the above changes is: 1. Use "task index + 1" as the TID reported to GDB 2. Report the tasks in natural order; don't complicate the code to make the paniced task first in the list. 3. Centralize modification of 'current_task_index' and 'regfile' in the new 'set_active_task' function, to improve encapsulation.		2021-06-18 16:02:10 +02:00
..
gdbstub.c	gdbstub: fix thread list generation	2021-06-18 16:02:10 +02:00
packet.c	tools: Mass fixing of empty prototypes (for -Wstrict-prototypes)	2019-08-01 16:28:56 +07:00