add_hw_breakpoint called on every step

[gz]

Hi Daniel,

I am wondering if maybe I'm did something wrong with my implementation: If I run a debug session where I set a HW breakpoint and then use stepi to go through code, the add_hw_breakpoint function is invoked again and again (for the same breakpoint) after every stepi completes. From the API I'd have guessed that I need to persist this BP until remove_hw_breakpoint is called eventually.

If this is what I should expect, I guess the right approach here is then for me to just delete breakpoints every time I'm going to execute the gdb state machine and expect it to reconfigure everything for me (e.g., which pretty much means I don't have to keep any state about breakpoints in target) or maybe it's better to just check if the breakpoint is already installed for the given address and ignore the request (that would be fine as long as I can expect that remove_hw_breakpoint is def. called whenever this BP isn't needed anymore)?

Either way would for implementation, I am mainly just not sure if this is intended behavior of add_hw_breakpoint.

[daniel5151]

Hey Gerd,

If possible, could you please post a trace log of the GDB RSP packets? Incoming packets get logged via this log::trace! statement, and outgoing packets are logged via this log::trace! statement.

It seems I've marked that latter log statement with #[cfg(feature = "std")], when it probably should be #[cfg(feature = "alloc")] (or more likely, a dedicated feature = "trace-pkts").

I see you're using alloc in your implementation, so you may need to fork + tweak gdbstub to get response logging working. Sorry about that!

In the meantime... I believe the GDB Client will actually clear + reset breakpoint whenever it resumes the target, so the behavior you're seeing might be reasonable. Is remove_hw_breakpoint being hit after every stepi as well, or is it just add_hw_breakpoint?

[gz]

Hi Daniel, Yes that's correct, gdbstub currently calls add_hw_breakpoint every time to reset the same breakpoint again (but never remove_hw_breakpoint).

This is the gdb session (fails here after the 5th stepi because it runs out of hardware breakpoints to use).

➜  kernel git:(gdbstub) ✗ gdb ../target/x86_64-uefi/debug/esp/kernel 
GNU gdb (Ubuntu 9.2-0ubuntu1~20.04) 9.2
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ../target/x86_64-uefi/debug/esp/kernel...
warning: remote target does not support file transfer, attempting to access files from local filesystem.
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
nrk::arch::_start (argc=70369785573376, _argv=0x9) at kernel/src/arch/x86_64/mod.rs:790
790             cmdline,
(gdb) hbreak xmain
Hardware assisted breakpoint 1 at 0x40003cebff8b: file kernel/src/integration_main.rs, line 609.
(gdb) stepi
0x000040003cf0297b      790             cmdline,
(gdb) stepi
0x000040003cf02983      790             cmdline,
(gdb) stepi
0x000040003cf02988      790             cmdline,
(gdb) stepi
0x000040003d1597d0 in memcpy ()
(gdb) stepi
Warning:
Cannot insert hardware breakpoint 1.
Could not insert hardware breakpoints:
You may have requested too many hardware breakpoints/watchpoints.

Command aborted.
(gdb) 

This is the trace from the stub:

➜  kernel git:(gdbstub) ✗ python3 run.py --kfeatures test-vmxnet-smoltcp gdb --cmd "log='gdbstub=trace,nrk::arch::gdb=trace'" --nic vmxnet3 --qemu-cores 1 --qemu-nodes 0 --qemu-memory 1024 --qemu-monitor --gdb

 815892132 [INFO ] - nrk::arch::gdb: Waiting for a GDB connection (I/O port 0x2f8)...       
 825800072 [INFO ] - nrk::arch::gdb: Use `target remote localhost:1234` in gdb to connect.  
21238440348 [INFO ] - nrk::arch::gdb: Debugger connected.                                   
21243701434 [TRACE] - gdbstub::protocol::recv_packet: <-- +                                 
21272592624 [TRACE] - gdbstub::protocol::recv_packet: <-- $qSupported:multiprocess+;swbreak+
;hwbreak+;qRelocInsn+;fork-events+;vfork-events+;exec-events+;vContSupported+;QThreadEvents+
;no-resumed+;xmlRegisters=i386#6a                                                           
21298443468 [TRACE] - gdbstub::protocol::response_writer: --> $PacketSize=1000;vContSupporte
d+;multiprocess+;QStartNoAckMode+;hwbreak+;qXfer:features:read+#f2                          
21309119672 [TRACE] - gdbstub::protocol::recv_packet: <-- +                                 
21313764648 [TRACE] - gdbstub::protocol::recv_packet: <-- $vMustReplyEmpty#3a               
21317869610 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("vMustReplyEmpty")         
21321799938 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          
21325635744 [TRACE] - gdbstub::protocol::recv_packet: <-- +                                 
21330592708 [TRACE] - gdbstub::protocol::recv_packet: <-- $QStartNoAckMode#b0               
21339975142 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
21348071036 [TRACE] - gdbstub::protocol::recv_packet: <-- +                                 
21354884174 [TRACE] - gdbstub::protocol::recv_packet: <-- $Hgp0.0#ad                        
21361588808 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
21462580574 [TRACE] - gdbstub::protocol::recv_packet: <-- $qXfer:features:read:target.xml:0,
ffb#79                                                                                      
21473357298 [TRACE] - gdbstub::protocol::response_writer: --> $m<target version="1.0"><archi
tecture>i386:x86-64</architecture><feature name="org.gnu.gdb.i386.sse"></feature></target>#c
7                                                                                           
21487535264 [TRACE] - gdbstub::protocol::recv_packet: <-- $qXfer:features:read:target.xml:76
,ffb#b6                                                                                     
21493665166 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
21500814082 [TRACE] - gdbstub::protocol::recv_packet: <-- $qTStatus#49                      
21505601406 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("qTStatus")                
21510639488 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          
21606925828 [TRACE] - gdbstub::protocol::recv_packet: <-- $?#3f                             
21610737522 [TRACE] - gdbstub::protocol::response_writer: --> $S05#b8                       
21616370986 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
21620503704 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
21625971684 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
21629857128 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         21635465350 [TRACE] - gdbstub::protocol::recv_packet: <-- $qAttached:1#fa                   21640477264 [TRACE] - gdbstub::protocol::response_writer: --> $1#31                         21730230988 [TRACE] - gdbstub::protocol::recv_packet: <-- $Hc-1#09                          21733927756 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        21738485420 [TRACE] - gdbstub::protocol::recv_packet: <-- $qC#b4                            21742078470 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("qC")                      21745727072 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          21750680718 [TRACE] - gdbstub::protocol::recv_packet: <-- $qOffsets#4b                      21757193798 [TRACE] - gdbstub::protocol::response_writer: --> $Text=40003ce6a000;Data=40003ce6a000;Bss=40003ce6a000#26                                                                  21763158880 [TRACE] - gdbstub::protocol::recv_packet: <-- $g#67                             21766824728 [INFO ] - nrk::arch::gdb: read_registers                                        
21777090070 [TRACE] - gdbstub::protocol::response_writer: --> $00000000000000000000000000000
000e8d2483d00400000160000000000000039a33d3d00400000d88c423e00400000f08f423e004000008049393e0
040000000000000000000000000000000000000283a393e00400000d400000000000000010000000000000001000
0000000000004000000000000005403203f000000007329f03c00400000020000000800000010000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#35          
21862399112 [TRACE] - gdbstub::protocol::recv_packet: <-- $m63bf40,8#66                     
21866150974 [INFO ] - nrk::arch::gdb: read_addr 0x63bf40                                    
21869615888 [TRACE] - gdbstub::protocol::response_writer: --> $0000000000000000#86          
21875974776 [TRACE] - gdbstub::protocol::recv_packet: <-- $vFile:setfs:0#bf                 
21879992016 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("vFile:setfs:0")           
21883943554 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          
21893966032 [TRACE] - gdbstub::protocol::recv_packet: <-- $vFile:open:6a7573742070726f62696e
67,0,1c0#ed                                                                                 
21900326944 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("vFile:open:6a7573742070726
f62696e67,0,1c0")
21906949976 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          
22003591468 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
22007887010 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
22013499298 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
22017643112 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
22039095170 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02973,1#8f               
22044227422 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02973                              
22048904580 [TRACE] - gdbstub::protocol::response_writer: --> $48#6c                        
22143764242 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02973,1#8f               
22147703890 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02973                              
22151397938 [TRACE] - gdbstub::protocol::response_writer: --> $48#6c                        
22179069434 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003e428de0,8#c4               
22183097250 [INFO ] - nrk::arch::gdb: read_addr 0x40003e428de0                              
22187608594 [TRACE] - gdbstub::protocol::response_writer: --> $0070123e00400000#d1          
22194231272 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003e428de8,8#cc               
22198327920 [INFO ] - nrk::arch::gdb: read_addr 0x40003e428de8                              
22201999112 [TRACE] - gdbstub::protocol::response_writer: --> $0900000000000000#ed          
22293066970 [TRACE] - gdbstub::protocol::recv_packet: <-- $qSymbol::#5b                     
22296755072 [INFO ] - gdbstub::gdbstub_impl: Unknown command: Ok("qSymbol::")               
22300811854 [TRACE] - gdbstub::protocol::response_writer: --> $#00                          
28556367390 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cebff8b,1#51               
28560412166 [INFO ] - nrk::arch::gdb: read_addr 0x40003cebff8b                              
28564025898 [TRACE] - gdbstub::protocol::response_writer: --> $e8#9d                        
30948803252 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
30952886508 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
30956637324 [INFO ] - nrk::arch::gdb: added hw breakpoint 0x40003cebff8b                    
30961759384 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
30968474432 [TRACE] - gdbstub::protocol::recv_packet: <-- $vCont?#49                        
30975056334 [TRACE] - gdbstub::protocol::response_writer: --> $vCont;c;C;s;S#62             
30984364166 [TRACE] - gdbstub::protocol::recv_packet: <-- $vCont;s:p1.1;c:p1.-1#f7          
30989236614 [INFO ] - nrk::arch::gdb: resume_with =  Step                                   
30997734780 [INFO ] - nrk::arch::gdb: Stepping, set TF flag                                 
31006515464 [INFO ] - nrk::arch::gdb: stop reason is DoneStep                               
31013290952 [TRACE] - gdbstub::protocol::response_writer: --> $S05#b8                       
31106483570 [TRACE] - gdbstub::protocol::recv_packet: <-- $g#67                             
31116076290 [INFO ] - nrk::arch::gdb: read_registers                                        
31149526592 [TRACE] - gdbstub::protocol::response_writer: --> $00000000000000000000000000000
000e8d2483d00400000160000000000000039a33d3d00400000388d423e00400000f08f423e004000008049393e0
040000000000000000000000000000000000000283a393e00400000d400000000000000010000000000000001000
0000000000004000000000000005403203f000000007b29f03c00400000020100000800000010000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#35
31251399952 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf0297b,1#be               
31259913354 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf0297b                              
31267729872 [TRACE] - gdbstub::protocol::response_writer: --> $48#6c                        
31278498764 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf0297b,1#be               
31286928852 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf0297b                              
31294799972 [TRACE] - gdbstub::protocol::response_writer: --> $48#6c                        
31388685162 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
31399637758 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
31412880988 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
31424287624 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
31439359920 [TRACE] - gdbstub::protocol::recv_packet: <-- $z1,40003cebff8b,1#bb             
31450994896 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
33822223690 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
33833977608 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
33844986862 [INFO ] - nrk::arch::gdb: added hw breakpoint 0x40003cebff8b                    
33853161512 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
33864872752 [TRACE] - gdbstub::protocol::recv_packet: <-- $vCont;s:p1.1;c:p1.-1#f7          
33874339280 [INFO ] - nrk::arch::gdb: resume_with =  Step                                   
33883480746 [INFO ] - nrk::arch::gdb: Stepping, set TF flag                                 
33892801320 [INFO ] - nrk::arch::gdb: stop reason is DoneStep                               
33902866318 [TRACE] - gdbstub::protocol::response_writer: --> $S05#b8                       
33914268286 [TRACE] - gdbstub::protocol::recv_packet: <-- $g#67                             
33923806768 [INFO ] - nrk::arch::gdb: read_registers                                        
33957091832 [TRACE] - gdbstub::protocol::response_writer: --> $00000000000000000000000000000
000e8d2483d004000001600000000000000204d393e00400000388d423e00400000f08f423e004000008049393e0
040000000000000000000000000000000000000283a393e00400000d400000000000000010000000000000001000
0000000000004000000000000005403203f000000008329f03c00400000020100000800000010000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#d7
34066707732 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02983,1#90               
34077483976 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02983                              
34087428534 [TRACE] - gdbstub::protocol::response_writer: --> $ba#c3                        
34181366114 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02983,1#90               
34192222902 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02983                              
34202273318 [TRACE] - gdbstub::protocol::response_writer: --> $ba#c3                        
34215181008 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
34226860408 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
34240231436 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
34251068706 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
34348534338 [TRACE] - gdbstub::protocol::recv_packet: <-- $z1,40003cebff8b,1#bb             
34360043656 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
36533453408 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
36544560970 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
36554798392 [INFO ] - nrk::arch::gdb: added hw breakpoint 0x40003cebff8b                    
36565709632 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
36580135704 [TRACE] - gdbstub::protocol::recv_packet: <-- $vCont;s:p1.1;c:p1.-1#f7          
36591376750 [INFO ] - nrk::arch::gdb: resume_with =  Step                                   
36600468382 [INFO ] - nrk::arch::gdb: Stepping, set TF flag                                 
36609823530 [INFO ] - nrk::arch::gdb: stop reason is DoneStep                               
36619954694 [TRACE] - gdbstub::protocol::response_writer: --> $S05#b8                       
36631306870 [TRACE] - gdbstub::protocol::recv_packet: <-- $g#67                             
36640874866 [INFO ] - nrk::arch::gdb: read_registers                                        
36670519360 [TRACE] - gdbstub::protocol::response_writer: --> $00000000000000000000000000000
000e8d2483d004000004000000000000000204d393e00400000388d423e00400000f08f423e004000008049393e0
040000000000000000000000000000000000000283a393e00400000d400000000000000010000000000000001000
0000000000004000000000000005403203f000000008829f03c00400000020100000800000010000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#aa
36780402766 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02988,1#95               
36791193480 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02988                              
36801153526 [TRACE] - gdbstub::protocol::response_writer: --> $e8#9d                        
36814723926 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003cf02988,1#95               
36825477748 [INFO ] - nrk::arch::gdb: read_addr 0x40003cf02988                              
36835518282 [TRACE] - gdbstub::protocol::response_writer: --> $e8#9d                        
36848499278 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
36860003864 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
36955091298 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
36965978824 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
36979490322 [TRACE] - gdbstub::protocol::recv_packet: <-- $z1,40003cebff8b,1#bb             
36990994386 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
38637922402 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
38649000350 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
38659287774 [INFO ] - nrk::arch::gdb: added hw breakpoint 0x40003cebff8b                    
38670202180 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
38684600024 [TRACE] - gdbstub::protocol::recv_packet: <-- $vCont;s:p1.1;c:p1.-1#f7          
38695877698 [INFO ] - nrk::arch::gdb: resume_with =  Step                                   
38704998150 [INFO ] - nrk::arch::gdb: Stepping, set TF flag                                 
38714347160 [INFO ] - nrk::arch::gdb: stop reason is DoneStep                               
38724330400 [TRACE] - gdbstub::protocol::response_writer: --> $S05#b8                       
38814791636 [TRACE] - gdbstub::protocol::recv_packet: <-- $g#67                             
38824363682 [INFO ] - nrk::arch::gdb: read_registers                                        
38857500624 [TRACE] - gdbstub::protocol::response_writer: --> $00000000000000000000000000000
000e8d2483d004000004000000000000000204d393e00400000388d423e00400000f08f423e004000007849393e0
040000000000000000000000000000000000000283a393e00400000d400000000000000010000000000000001000
0000000000004000000000000005403203f00000000d097153d00400000020100000800000010000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx#ab
38968540858 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003d1597d0,1#8f               
38979354198 [INFO ] - nrk::arch::gdb: read_addr 0x40003d1597d0                              
38989294712 [TRACE] - gdbstub::protocol::response_writer: --> $f3#99                        
39002956840 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003d1597d0,1#8f               
39013734016 [INFO ] - nrk::arch::gdb: read_addr 0x40003d1597d0                              
39023755042 [TRACE] - gdbstub::protocol::response_writer: --> $f3#99                        
39116283478 [TRACE] - gdbstub::protocol::recv_packet: <-- $m40003e394940,40#96              
39127246298 [INFO ] - nrk::arch::gdb: read_addr 0x40003e394940                              
39149124198 [TRACE] - gdbstub::protocol::response_writer: --> $0449393e0040000004a9000000000
00039a33d3d004000001600000000000000000d3b3e00400000000d3b3e00400000f08f423e004000008d29f03c0
0400000#55
39173419590 [TRACE] - gdbstub::protocol::recv_packet: <-- $qfThreadInfo#bb                  
39185149242 [TRACE] - gdbstub::protocol::response_writer: --> $mp01.01#cd                   
39198176630 [TRACE] - gdbstub::protocol::recv_packet: <-- $qsThreadInfo#c8                  
39209031944 [TRACE] - gdbstub::protocol::response_writer: --> $l#6c                         
39308884840 [TRACE] - gdbstub::protocol::recv_packet: <-- $z1,40003cebff8b,1#bb             
39320424332 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        
41734543658 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
41746166478 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
41757866746 [TRACE] - gdbstub::protocol::response_writer: --> $E16#ac                       

[daniel5151]

Looking at the logs, I'm definitely seeing the behavior I was describing: the breakpoint is being continuously unset + set. e.g:

36979490322 [TRACE] - gdbstub::protocol::recv_packet: <-- $z1,40003cebff8b,1#bb             
36990994386 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a                        

38637922402 [TRACE] - gdbstub::protocol::recv_packet: <-- $Z1,40003cebff8b,1#9b             
38649000350 [INFO ] - nrk::arch::gdb: add hw breakpoint 0x40003cebff8b                      
38659287774 [INFO ] - nrk::arch::gdb: added hw breakpoint 0x40003cebff8b                    
38670202180 [TRACE] - gdbstub::protocol::response_writer: --> $OK#9a  

Can you please add a log statement to the start of your remove_hw_breakpoint and confirm that it is being hit + working correctly?

[gz]

Hm sorry this is pretty embarrassing. I didn't realize I didn't have a log statement in remove_hw_breakpoint and was under the impression it was there :/
remove_hw_breakpoint gets triggered, but probably just my remove logic seems broken. Sorry about wasting your time.

[daniel5151]

No worries 🙂

If anything, this discussion uncovered a small oversight in my tracing cfg logic, so thanks for that! I'll file a tracking issue to fix it...

[gz]

Thanks, sent you a pull request for this https://github.com/daniel5151/gdbstub/pull/78/files