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Make QStartNoAckMode optional #134

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bet4it opened this issue Mar 28, 2023 · 1 comment · Fixed by #135
Closed

Make QStartNoAckMode optional #134

bet4it opened this issue Mar 28, 2023 · 1 comment · Fixed by #135
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API-non-breaking Non-breaking API change new-api Add a new feature to the API (possibly non-breaking)

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@bet4it
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bet4it commented Mar 28, 2023

I want to use IDA Pro as a GDB client to connect the example program in my project udbserver:

$ cargo run --example server

IDA Pro asked me the PID to attach to, and failed to attach after I provided a pid:

 TRACE gdbstub::protocol::recv_packet > <-- +
 TRACE gdbstub::protocol::recv_packet > <-- $qSupported:xmlRegisters=i386,arm,mips#12
 TRACE gdbstub::protocol::response_writer > --> $PacketSize=1000;vContSupported+;multiprocess+;QStartNoAckMode+;swbreak+;hwbreak+;qXfer:features:read+#47
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $QStartNoAckMode#b0
 TRACE gdbstub::protocol::response_writer > --> $OK#9a
 TRACE gdbstub::protocol::recv_packet     > <-- $!#21
 INFO  gdbstub::stub::core_impl           > Unknown command: Ok("!")
 TRACE gdbstub::protocol::response_writer > --> $#00
 TRACE gdbstub::protocol::recv_packet     > <-- $Hg0#df
 TRACE gdbstub::protocol::response_writer > --> $OK#9a
 TRACE gdbstub::protocol::recv_packet     > <-- $qXfer:features:read:target.xml:0,fff#7d
 TRACE gdbstub::protocol::response_writer > --> $m
        <target version="1.0">
            <architecture>arm</architecture>
            <feature name="org.gnu.gdb.arm.core">
              <reg name="r0" bitsize="32" type="uint32"/>
              <reg name="r1" bitsize="32" type="uint32"/>
              <reg name="r2" bitsize="32" type="uint32"/>
              <reg name="r3" bitsize="32" type="uint32"/>
              <reg name="r4" bitsize="32" type="uint32"/>
              <reg name="r5" bitsize="32" type="uint32"/>
              <reg name="r6" bitsize="32" type="uint32"/>
              <reg name="r7" bitsize="32" type="uint32"/>
              <reg name="r8" bitsize="32" type="uint32"/>
              <reg name="r9" bitsize="32" type="uint32"/>
              <reg name="r10" bitsize="32" type="uint32"/>
              <reg name="r11" bitsize="32" type="uint32"/>
              <reg name="r12" bitsize="32" type="uint32"/>
              <reg name="sp" bitsize="32" type="data_ptr"/>
              <reg name="lr" bitsize="32"/>
              <reg name="pc" bitsize="32" type="code_ptr"/>
              <reg name="cpsr" bitsize="32"/>
            </feature>
        </target>
    #5f
 TRACE gdbstub::protocol::recv_packet     > <-- $?#3f
 TRACE gdbstub::protocol::response_writer > --> $T05thread:01;#07
 TRACE gdbstub::protocol::recv_packet     > <-- $vAttach;1#37
 INFO  gdbstub::stub::core_impl           > Unknown command: Ok("vAttach;1")
 TRACE gdbstub::protocol::response_writer > --> $#00

But if QStartNoAckMode is disabled, IDA Pro won't ask for the PID and everything works well:

 TRACE gdbstub::protocol::recv_packet > <-- +
 TRACE gdbstub::protocol::recv_packet > <-- $qSupported:xmlRegisters=i386,arm,mips#12
 TRACE gdbstub::protocol::response_writer > --> $PacketSize=1000;vContSupported+;multiprocess+;swbreak+;hwbreak+;qXfer:features:read+#31
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $!#21
 INFO  gdbstub::stub::core_impl           > Unknown command: Ok("!")
 TRACE gdbstub::protocol::response_writer > --> $#00
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $Hg0#df
 TRACE gdbstub::protocol::response_writer > --> $OK#9a
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $qXfer:features:read:target.xml:0,fff#7d
 TRACE gdbstub::protocol::response_writer > --> $m
        <target version="1.0">
            <architecture>arm</architecture>
            <feature name="org.gnu.gdb.arm.core">
              <reg name="r0" bitsize="32" type="uint32"/>
              <reg name="r1" bitsize="32" type="uint32"/>
              <reg name="r2" bitsize="32" type="uint32"/>
              <reg name="r3" bitsize="32" type="uint32"/>
              <reg name="r4" bitsize="32" type="uint32"/>
              <reg name="r5" bitsize="32" type="uint32"/>
              <reg name="r6" bitsize="32" type="uint32"/>
              <reg name="r7" bitsize="32" type="uint32"/>
              <reg name="r8" bitsize="32" type="uint32"/>
              <reg name="r9" bitsize="32" type="uint32"/>
              <reg name="r10" bitsize="32" type="uint32"/>
              <reg name="r11" bitsize="32" type="uint32"/>
              <reg name="r12" bitsize="32" type="uint32"/>
              <reg name="sp" bitsize="32" type="data_ptr"/>
              <reg name="lr" bitsize="32"/>
              <reg name="pc" bitsize="32" type="code_ptr"/>
              <reg name="cpsr" bitsize="32"/>
            </feature>
        </target>
    #5f
 TRACE gdbstub::protocol::recv_packet     > <-- $?#3f
 TRACE gdbstub::protocol::response_writer > --> $T05thread:01;#07
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $?#3f
 TRACE gdbstub::protocol::response_writer > --> $T05thread:01;#07
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $qfThreadInfo#bb
 TRACE gdbstub::protocol::response_writer > --> $m01#ce
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $qsThreadInfo#c8
 TRACE gdbstub::protocol::response_writer > --> $l#6c
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $g#67
 TRACE gdbstub::protocol::response_writer > --> $00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000d3010040#ce
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $qXfer:features:read:target.xml:0,fff#7d
 TRACE gdbstub::protocol::response_writer > --> $m
        <target version="1.0">
            <architecture>arm</architecture>
            <feature name="org.gnu.gdb.arm.core">
              <reg name="r0" bitsize="32" type="uint32"/>
              <reg name="r1" bitsize="32" type="uint32"/>
              <reg name="r2" bitsize="32" type="uint32"/>
              <reg name="r3" bitsize="32" type="uint32"/>
              <reg name="r4" bitsize="32" type="uint32"/>
              <reg name="r5" bitsize="32" type="uint32"/>
              <reg name="r6" bitsize="32" type="uint32"/>
              <reg name="r7" bitsize="32" type="uint32"/>
              <reg name="r8" bitsize="32" type="uint32"/>
              <reg name="r9" bitsize="32" type="uint32"/>
              <reg name="r10" bitsize="32" type="uint32"/>
              <reg name="r11" bitsize="32" type="uint32"/>
              <reg name="r12" bitsize="32" type="uint32"/>
              <reg name="sp" bitsize="32" type="data_ptr"/>
              <reg name="lr" bitsize="32"/>
              <reg name="pc" bitsize="32" type="code_ptr"/>
              <reg name="cpsr" bitsize="32"/>
            </feature>
        </target>
    #5f
 TRACE gdbstub::protocol::recv_packet     > <-- $pf#d6
 TRACE gdbstub::protocol::response_writer > --> $00100000#0c
 TRACE gdbstub::protocol::recv_packet     > <-- +
 TRACE gdbstub::protocol::recv_packet     > <-- $g#67
 TRACE gdbstub::protocol::response_writer > --> $00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000d3010040#ce
 TRACE gdbstub::protocol::recv_packet     > <-- +

Should we make QStartNoAckMode optional to support IDA Pro? Do we have other ways to solve it?
@daniel5151
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Sure, I wouldn't opposed to merging something like Target::supports_no_ack_mode (along the same lines as Target::supports_x_packet) that lets the target dictate whether it wants to support no ack mode.

Shouldn't be too hard to do, if you want to send a PR for it?

Though for what it's worth: that behavior doesn't seem like a gdbstub bug per-se. It seems IDA is making some weird assumptions about how GDB targets behave...

Maybe it assumes that bare-metal targets are typically debugged over serial, and therefore would use ack packets, and hence wouldn't support vAttach?

@daniel5151 daniel5151 added API-non-breaking Non-breaking API change new-api Add a new feature to the API (possibly non-breaking) labels Mar 28, 2023
@bet4it bet4it mentioned this issue Mar 30, 2023
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@daniel5151 daniel5151 mentioned this issue Apr 10, 2023
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Toggle support for QStartNoAckMode bet4it/gdbstub
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