Add setting to require hardware breakpoints.

When debugging read-only memory we cannot use software breakpoint. We
already have support for hardware breakpoints and users can specify them
with `-H`. However, there's no option to force LLDB to use hardware
breakpoints internally, for example while stepping.

This patch adds a setting target.require-hardware-breakpoint that forces
LLDB to always use hardware breakpoints. Because hardware breakpoints
are a limited resource and can fail to resolve, this patch also extends
error handling in thread plans, where breakpoints are used for stepping.

Differential revision: https://reviews.llvm.org/D54221

llvm-svn: 346920

4 files changed, 121 insertions, 1 deletions

diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/Makefile b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/Makefile
new file mode 100644
index 00000000000..7934cd5db42
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/Makefile
@@ -0,0 +1,9 @@
+LEVEL = ../../../make
+
+C_SOURCES := main.c
+
+ifneq (,$(findstring icc,$(CC)))
+    CFLAGS += -debug inline-debug-info
+endif
+
+include $(LEVEL)/Makefile.rules
diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/TestRequireHWBreakpoints.py b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/TestRequireHWBreakpoints.py
new file mode 100644
index 00000000000..1a1ee2eaa89
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/TestRequireHWBreakpoints.py
@@ -0,0 +1,102 @@
+"""
+Test require hardware breakpoints.
+"""
+
+from __future__ import print_function
+
+import os
+import time
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class BreakpointLocationsTestCase(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test_breakpoint(self):
+        """Test regular breakpoints when hardware breakpoints are required."""
+        self.build()
+        exe = self.getBuildArtifact("a.out")
+        target = self.dbg.CreateTarget(exe)
+
+        self.runCmd("settings set target.require-hardware-breakpoint true")
+
+        breakpoint = target.BreakpointCreateByLocation("main.c", 1)
+        self.assertTrue(breakpoint.IsHardware())
+
+    def test_step_range(self):
+        """Test stepping when hardware breakpoints are required."""
+        self.build()
+
+        _, _, thread, _ = lldbutil.run_to_line_breakpoint(
+            self, lldb.SBFileSpec("main.c"), 1)
+
+        self.runCmd("settings set target.require-hardware-breakpoint true")
+
+        # Ensure we fail in the interpreter.
+        self.expect("thread step-in")
+        self.expect("thread step-in", error=True)
+
+        # Ensure we fail when stepping through the API.
+        error = lldb.SBError()
+        thread.StepInto('', 4, error)
+        self.assertTrue(error.Fail())
+        self.assertTrue("Could not create hardware breakpoint for thread plan"
+                        in error.GetCString())
+
+    def test_step_out(self):
+        """Test stepping out when hardware breakpoints are required."""
+        self.build()
+
+        _, _, thread, _ = lldbutil.run_to_line_breakpoint(
+            self, lldb.SBFileSpec("main.c"), 1)
+
+        self.runCmd("settings set target.require-hardware-breakpoint true")
+
+        # Ensure this fails in the command interpreter.
+        self.expect("thread step-out", error=True)
+
+        # Ensure we fail when stepping through the API.
+        error = lldb.SBError()
+        thread.StepOut(error)
+        self.assertTrue(error.Fail())
+        self.assertTrue("Could not create hardware breakpoint for thread plan"
+                        in error.GetCString())
+
+    def test_step_over(self):
+        """Test stepping over when hardware breakpoints are required."""
+        self.build()
+
+        _, _, thread, _ = lldbutil.run_to_line_breakpoint(
+            self, lldb.SBFileSpec("main.c"), 7)
+
+        self.runCmd("settings set target.require-hardware-breakpoint true")
+
+        # Step over doesn't fail immediately but fails later on.
+        self.expect("thread step-over")
+        self.expect(
+            "process status",
+            substrs=[
+                'step over failed',
+                'Could not create hardware breakpoint for thread plan'
+            ])
+
+    def test_step_until(self):
+        """Test stepping until when hardware breakpoints are required."""
+        self.build()
+
+        _, _, thread, _ = lldbutil.run_to_line_breakpoint(
+            self, lldb.SBFileSpec("main.c"), 7)
+
+        self.runCmd("settings set target.require-hardware-breakpoint true")
+
+        self.expect("thread until 5", error=True)
+
+        # Ensure we fail when stepping through the API.
+        error = thread.StepOverUntil(lldb.SBFrame(), lldb.SBFileSpec(), 5)
+        self.assertTrue(error.Fail())
+        self.assertTrue("Could not create hardware breakpoint for thread plan"
+                        in error.GetCString())
diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/main.c b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/main.c
new file mode 100644
index 00000000000..7d49a57d4c7
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/breakpoint/require_hw_breakpoints/main.c
@@ -0,0 +1,9 @@
+int break_on_me() {
+  int i = 10;
+  i++;
+  return i;
+}
+
+int main() {
+  return break_on_me();
+}
diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/step_scripted/TestStepScripted.py b/lldb/packages/Python/lldbsuite/test/functionalities/step_scripted/TestStepScripted.py
index 1c254c56476..a111ede6739 100644
--- a/lldb/packages/Python/lldbsuite/test/functionalities/step_scripted/TestStepScripted.py
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/step_scripted/TestStepScripted.py
@@ -35,7 +35,7 @@ class StepScriptedTestCase(TestBase):
         self.assertEqual("foo", frame.GetFunctionName())
 
         err = thread.StepUsingScriptedThreadPlan(name)
-        self.assertTrue(err.Success(), "Failed to step out")
+        self.assertTrue(err.Success(), err.GetCString())
 
         frame = thread.GetFrameAtIndex(0)
         self.assertEqual("main", frame.GetFunctionName())