GDB stub small fixes: out-of-bounds and wrong packet reply in 'qfThreadInfo' #3666
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The issue happens when the ENABLE_GDBSTUB_LOG flag is set, more specifically within the gdbstub_client_respond() function. This is due to the fact that the string 'GDB Stub: Sending response: ' and the newline character '\n' total 29 characters. When combined with the 995 characters of client->response, the total is 1024 bytes. However, the pclog_ex() buffer size is also 1024 bytes, leaving no room for the null terminator '\0'. As a result, when attempting to print the text on the screen, a segmentation fault occurs. This commit fixes this by decreasing the response text's size by one byte.
When GDB sends the 'qfThreadInfo' packet, one of the possible responses is 'm thread-id', as specified in [1]. However, contrary to what the documentation implies, there is no space between 'm' and the thread-id. In the current approach, GDB isn't even able to recognize that there's any active thread, as the code sends "m 1" instead of "m1". This commit addresses this by removing the space in the response. Ref: [1]: https://sourceware.org/gdb/onlinedocs/gdb/General-Query-Packets.html
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Summary
This PR brings two small fixes that prevents from using GDB stub normally:
Fixes an out-of-bounds issue when the
ENABLE_GDBSTUB_LOGflag is set.Remove an additional space in the response of the 'qfThreadInfo' package that prevents GDB from recognizing the current thread.
With these fixes, GDB now works like a charm here.
(There is a more detailed explanation of each fix in the commit messages)
Checklist
References
https://sourceware.org/gdb/onlinedocs/gdb/General-Query-Packets.html