Qdb Arm render and Arm branch predictor bug

[antcpl]

Describe the bug
When trying to debug a cortex M target, two bugs happen one in render_arm.py, the other in branch_predictor_arm.py. Both are the same : cpsr = self.read_reg('cpsr'), this call uses the cpsr that doesn't exists on Armv7M, it's xpsr.

Screenshots
Traceback (most recent call last):
File "/home/antoine/branch_dev_qiling/qiling/examples/mcu/cortex_M/general_script.py", line 50, in
ql.run()
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core.py", line 581, in run
debugger = debugger(self)
^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 91, in init
self.dbg_hook([addr for addr in init_hook if int(addr, 0) != self.ql.loader.entry_point])
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 150, in dbg_hook
self.ql.os.run()
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/os/mcu/mcu.py", line 80, in run
self.ql.emu_start(current_address, 0, count=1)
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core.py", line 774, in emu_start
raise self.internal_exception
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core_hooks.py", line 141, in wrapper
return callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core_hooks.py", line 226, in _hook_trace_cb
ret = hook.call(ql, addr, size)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core_hooks_types.py", line 25, in call
return self.callback(ql, *args)
^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 126, in __bp_handler
self.do_context()
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 401, in do_context
self.render.context_reg()
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/render/render.py", line 73, in wrapper
wrapped(*args, **kwargs)
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/render/render.py", line 238, in context_reg
self.print_mode_info()
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/render/render_arm.py", line 18, in print_mode_info
cpsr = self.read_reg('cpsr')
^^^^^^^^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/context.py", line 48, in read_reg
return self.ql.arch.regs.read(reg)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/arch/register.py", line 58, in read
register = self.register_mapping[register.lower()]
~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
KeyError: 'cpsr'

Additional context
I've just tried to replace with xpsr string this work perfectly, you just have to find a way to make the correct call.

[elicn]

@antcpl, good catch. I've created a quick fix for it.
Please pull the fix-qdb-cortexm branch and confirm it fixes the problem.

[antcpl]

Hi, I've pulled the branch and tested. A small problem occured which kind look the same as that we had before, here is the error dump :

  File "/home/antoine/branch_dev_qiling/qiling/examples/mcu/cortex_M/general_script.py", line 50, in <module>
    ql.run()
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/core.py", line 581, in run
    debugger = debugger(self)
               ^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 91, in __init__
    self.dbg_hook([addr for addr in init_hook if int(addr, 0) != self.ql.loader.entry_point])
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 162, in dbg_hook
    self.cmdloop()
  File "/usr/lib/python3.12/cmd.py", line 138, in cmdloop
    stop = self.onecmd(line)
           ^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/cmd.py", line 217, in onecmd
    return func(arg)
           ^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/utils.py", line 286, in magic
    func(self, *args, **kwargs)
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 37, in inner
    func(self, *args, **kwargs)
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 55, in inner
    func(self, *args, **kwargs)
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 250, in do_step_in
    self.do_context()
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/qdb.py", line 403, in do_context
    self.render.context_asm()
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/render/render.py", line 73, in wrapper
    wrapped(*args, **kwargs)
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/render/render_arm.py", line 40, in context_asm
    prediction = self.predictor.predict()
                 ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/branch_predictor/branch_predictor_arm.py", line 164, in predict
    going, _ = __is_taken(insn.cc)
               ^^^^^^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/branch_predictor/branch_predictor_arm.py", line 125, in __is_taken
    flags = self.get_cond_flags()
            ^^^^^^^^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/branch_predictor/branch_predictor_arm.py", line 34, in get_cond_flags
    cpsr = self.read_reg(self._flags_reg)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/debugger/qdb/context.py", line 48, in read_reg
    return self.ql.arch.regs.read(reg)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/antoine/branch_dev_qiling/qilingenv/lib/python3.12/site-packages/qiling/arch/register.py", line 58, in read
    register = self.register_mapping[register.lower()]
               ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
KeyError: 'cpsr' 

This happens on the first branch instruction that is executed (first time the branch_predictor is fully executed).
I've looked around a bit, I think there just is a small oversight here : in branch_predictor_arm.py (line 264) :
Version in the branch :

class BranchPredictorCORTEX_M(BranchPredictorARM):
    """Branch Predictor for ARM Cortex-M.
    """

Corrected :

class BranchPredictorCORTEX_M(BranchPredictorARM, ArchCORTEX_M):
    """Branch Predictor for ARM Cortex-M.
    """

Tested and worked with the correction.

[elicn]

Ah, this is indeed an oversight.
I'll submit a fix soon.

[elicn]

Should be fixed now.
Please let me know if we need to re-open this.