Add stepover, small fixes for ARM

pwndbg/commands/next.py

@@ -39,3 +39,16 @@ def nextc(*args):
     """Breaks at the next call instruction"""
     nextcall(*args)
 
+
+@pwndbg.commands.Command
+@pwndbg.commands.OnlyWhenRunning
+def stepover(*args):
+    """Sets a breakpoint on the instruction after this one"""
+    pwndbg.next.break_on_next(*args)
+
+
+@pwndbg.commands.Command
+@pwndbg.commands.OnlyWhenRunning
+def so(*args):
+    stepover(*args)
+

pwndbg/disasm/__init__.py

@@ -118,6 +118,10 @@ def near(address, instructions=1):
     # Now find all of the instructions moving forward.
     insn  = current
     while insn and len(insns) < 1+(2*instructions):
+        # In order to avoid annoying cycles where the current instruction
+        # is a branch, which evaluates to true, and jumps back a short
+        # number of instructions.
+
         insn = one(insn.next)
         if insn:
             insns.append(insn)

pwndbg/disasm/arch.py

@@ -94,7 +94,7 @@ class DisassemblyAssistant(object):
         if next_addr is None:
             next_addr = instruction.address + instruction.size
 
-        instruction.next = next_addr
+        instruction.next = next_addr & pwndbg.arch.ptrmask
 
     def next(self, instruction):
         """

pwndbg/disasm/arm.py

@@ -14,7 +14,7 @@ import pwndbg.disasm.arch
 
 
 class DisassemblyAssistant(pwndbg.disasm.arch.DisassemblyAssistant):
-    def memory_sz(self, instruction, operand):
+    def memory_sz(self, instruction, op):
         segment = ''
         parts   = []
 
@@ -29,18 +29,20 @@ class DisassemblyAssistant(pwndbg.disasm.arch.DisassemblyAssistant):
             scale = op.mem.scale
             parts.append("%s*%#x" % (index, scale))
 
-        return "[%s]" % (segment, ', '.join(parts))
+        return "[%s]" % (', '.join(parts))
 
     def immediate_sz(self, instruction, operand):
-        imm = self.immediate(instruction, operand)
-        imm = self.arch.signed(imm)
+        return '#' + super(DisassemblyAssistant, self).immediate_sz(instruction, operand)
 
-        if abs(imm) < 0x10:
-            return '#%i' % imm
+    def condition(self, instruction):
 
-        return '#%#x' % imm
+        # We can't reason about anything except the current instruction
+        if instruction.cc == ARM_CC_AL:
+            return None
+
+        if instruction.address != pwndbg.regs.pc:
+            return False
 
-    def taken(self, instruction):
         cpsr = pwndbg.regs.cpsr
 
         N = cpsr & (1<<31)
@@ -63,7 +65,6 @@ class DisassemblyAssistant(pwndbg.disasm.arch.DisassemblyAssistant):
             ARM_CC_LT: N != V,
             ARM_CC_GT: not Z and (N==V),
             ARM_CC_LE: Z or (N != V),
-            # ARM_CC_AL: 1,
         }.get(instruction.id, None)
 
 assistant = DisassemblyAssistant('arm')

pwndbg/next.py

@@ -37,7 +37,7 @@ def break_next_branch(address=None):
 
     if ins:
         gdb.Breakpoint("*%#x" % ins.address, internal=True, temporary=True)
-        gdb.execute('continue')
+        gdb.execute('continue', from_tty=False, to_string=True)
         return ins
 
 def break_next_call(address=None):
@@ -50,3 +50,11 @@ def break_next_call(address=None):
         if capstone.CS_GRP_CALL in ins.groups:
             return ins
 
+def break_on_next(address=None):
+    address = address or pwndbg.regs.pc
+    ins = pwndbg.disasm.one(address)
+
+    gdb.Breakpoint("*%#x" % (ins.address + ins.size), temporary=True)
+    gdb.execute('continue', from_tty=False, to_string=True)
+
+