add stepover command (#1086)

This pull request addresses a limitation in GDB where the "nexti" and "next" commands fail to step over call instructions properly

docs/commands/stepover.md

@@ -0,0 +1,16 @@
+## Command `stepover`
+
+The stepover command simplifies the process of stepping over instructions by continuing to a
+temporary breakpoint at the next instruction.
+
+This feature is particularly useful for stepping over call/rep instructions.
+
+Ex: Step over call instruction
+
+```text
+stepover
+```
+
+```bash
+gef➤  stepover
+```

gef.py

@@ -4498,6 +4498,15 @@ def stop(self) -> bool:
         return True
 
 
+class JustSilentStopBreakpoint(gdb.Breakpoint):
+    """When hit, this temporary breakpoint stop the execution."""
+
+    def __init__(self, loc: str) -> None:
+        super().__init__(loc, gdb.BP_BREAKPOINT, temporary=True)
+        self.silent = True
+        return
+
+
 #
 # Context Panes
 #
@@ -6157,6 +6166,28 @@ def do_invoke(self, _: List[str], **kwargs: Any) -> None:
         return
 
 
+@register
+class StepoverCommand(GenericCommand):
+    """Breaks on the instruction immediately following this one. Ex: Step over call instruction"""
+
+    _cmdline_ = "stepover"
+    _syntax_  = (f"{_cmdline_}"
+                "\n\tBreaks on the instruction immediately following this one. Ex: Step over call instruction.")
+    _aliases_ = ["so",]
+    _example_ = [f"{_cmdline_}",]
+
+    def __init__(self) -> None:
+        super().__init__(complete=gdb.COMPLETE_LOCATION)
+        return
+
+    @only_if_gdb_running
+    def do_invoke(self, _: List[str]) -> None:
+        target_addr = gef_next_instruction(parse_address("$pc")).address
+        JustSilentStopBreakpoint("".join(["*",  str(target_addr)]))
+        gdb.execute("continue")
+        return
+
+
 @register
 class NopCommand(GenericCommand):
     """Patch the instruction(s) pointed by parameters with NOP. Note: this command is architecture

mkdocs.yml

@@ -63,6 +63,7 @@ nav:
   - search-pattern: commands/search-pattern.md
   - shellcode: commands/shellcode.md
   - stub: commands/stub.md
+  - stepover: commands/stepover.md
   - skipi: commands/skipi.md
   - theme: commands/theme.md
   - tmux-setup: commands/tmux-setup.md

tests/commands/stepover.py

@@ -0,0 +1,44 @@
+"""
+`stepover` command test module
+"""
+
+import pytest
+
+from tests.base import RemoteGefUnitTestGeneric
+from tests.utils import ARCH, ERROR_INACTIVE_SESSION_MESSAGE, p32, p64, u16, u32
+
+
+class Stepover(RemoteGefUnitTestGeneric):
+    """`stepover` command test module"""
+
+    cmd = "stepover"
+
+    def test_cmd_stepover_inactive(self):
+        gdb = self._gdb
+        res = gdb.execute(f"{self.cmd}", to_string=True)
+        self.assertEqual(ERROR_INACTIVE_SESSION_MESSAGE, res)
+
+    @pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
+    def test_cmd_stepover(self):
+        gdb = self._gdb
+        gef = self._gef
+
+        payload = b"\xe8\x05\x00\x00\x00\x90\x90\x6a\x00\xc3\xb8\x69\x69\x69\x69\xc3"
+        '''
+        call movtag <- 'stepover' execution from this point
+        nop <- 'stepover' should stops here and eax value should be 0x69696969
+        nop
+        push 0
+        ret <- if something fails we want a specific crash
+        movtag:
+        mov eax, 0x69696969
+        ret
+        '''
+
+        gdb.execute("start")
+        gef.memory.write(gef.arch.pc, payload)
+        res = gdb.execute(self.cmd, to_string=True)
+        assert res
+        mem = u16(gef.memory.read(gef.arch.pc, 2))  # read 2 bytes
+        self.assertEqual(0x9090, mem)  # 2 nops
+        self.assertEqual(0x69696969, gef.arch.register("$eax"))