[lldb] Add SBValue::GetValueAsAddress API

lldb/bindings/interface/SBValueDocstrings.i

@@ -135,6 +135,26 @@ linked list."
 %feature("docstring", "Expands nested expressions like .a->b[0].c[1]->d."
 ) lldb::SBValue::GetValueForExpressionPath;
 
+%feature("docstring", "
+      Return the value as an address.  On failure, LLDB_INVALID_ADDRESS
+      will be returned.  On architectures like AArch64, where the
+      top (unaddressable) bits can be used for authentication,
+      memory tagging, or top byte ignore,  this method will return
+      the value with those top bits cleared.
+
+      GetValueAsUnsigned returns the actual value, with the
+      authentication/Top Byte Ignore/Memory Tagging Extension bits.
+
+      Calling this on a random value which is not a pointer is
+      incorrect.  Call GetType().IsPointerType() if in doubt.
+
+      An SB API program may want to show both the literal byte value
+      and the address it refers to in memory.  These two SBValue
+      methods allow SB API writers to behave appropriately for their
+      interface."
+) lldb::SBValue::GetValueAsAddress;
+
+
 %feature("doctstring", "
     Returns the number for children.
 

lldb/include/lldb/API/SBValue.h

@@ -68,6 +68,8 @@ class LLDB_API SBValue {
 
   uint64_t GetValueAsUnsigned(uint64_t fail_value = 0);
 
+  lldb::addr_t GetValueAsAddress();
+
   ValueType GetValueType();
 
   // If you call this on a newly created ValueObject, it will always return

lldb/source/API/SBValue.cpp

@@ -909,6 +909,25 @@ uint64_t SBValue::GetValueAsUnsigned(uint64_t fail_value) {
   return fail_value;
 }
 
+lldb::addr_t SBValue::GetValueAsAddress() {
+  addr_t fail_value = LLDB_INVALID_ADDRESS;
+  ValueLocker locker;
+  lldb::ValueObjectSP value_sp(GetSP(locker));
+  if (value_sp) {
+    bool success = true;
+    uint64_t ret_val = fail_value;
+    ret_val = value_sp->GetValueAsUnsigned(fail_value, &success);
+    if (!success)
+      return fail_value;
+    ProcessSP process_sp = m_opaque_sp->GetProcessSP();
+    if (!process_sp)
+      return ret_val;
+    return process_sp->FixDataAddress(ret_val);
+  }
+
+  return fail_value;
+}
+
 bool SBValue::MightHaveChildren() {
   LLDB_INSTRUMENT_VA(this);
 

lldb/test/API/clear-sbvalue-nonaddressable-bits/Makefile

@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules

lldb/test/API/clear-sbvalue-nonaddressable-bits/TestClearSBValueNonAddressableBits.py

@@ -0,0 +1,59 @@
+"""Test that SBValue clears non-addressable bits"""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestClearSBValueNonAddressableBits(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    # On AArch64 systems, the top bits that are not used for
+    # addressing may be used for TBI, MTE, and/or pointer
+    # authentication.
+    @skipIf(archs=no_match(["aarch64", "arm64", "arm64e"]))
+
+    # Only run this test on systems where TBI is known to be
+    # enabled, so the address mask will clear the TBI bits.
+    @skipUnlessPlatform(["linux"] + lldbplatformutil.getDarwinOSTriples())
+    def test(self):
+        self.source = "main.c"
+        self.build()
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec(self.source, False)
+        )
+
+        if self.TraceOn():
+            self.runCmd("frame variable")
+            self.runCmd("frame variable &count &global")
+
+        frame = thread.GetFrameAtIndex(0)
+
+        count_p = frame.FindVariable("count_p")
+        count_invalid_p = frame.FindVariable("count_invalid_p")
+        self.assertEqual(
+            count_p.GetValueAsUnsigned(), count_invalid_p.GetValueAsAddress()
+        )
+        self.assertNotEqual(
+            count_invalid_p.GetValueAsUnsigned(), count_invalid_p.GetValueAsAddress()
+        )
+        self.assertEqual(5, count_p.Dereference().GetValueAsUnsigned())
+        self.assertEqual(5, count_invalid_p.Dereference().GetValueAsUnsigned())
+
+        global_p = frame.FindVariable("global_p")
+        global_invalid_p = frame.FindVariable("global_invalid_p")
+        self.assertEqual(
+            global_p.GetValueAsUnsigned(), global_invalid_p.GetValueAsAddress()
+        )
+        self.assertNotEqual(
+            global_invalid_p.GetValueAsUnsigned(), global_invalid_p.GetValueAsAddress()
+        )
+        self.assertEqual(10, global_p.Dereference().GetValueAsUnsigned())
+        self.assertEqual(10, global_invalid_p.Dereference().GetValueAsUnsigned())
+
+        main_p = frame.FindVariable("main_p")
+        main_invalid_p = frame.FindVariable("main_invalid_p")
+        self.assertEqual(
+            main_p.GetValueAsUnsigned(), main_invalid_p.GetValueAsAddress()
+        )

lldb/test/API/clear-sbvalue-nonaddressable-bits/main.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+int global = 10;
+
+int main() {
+  int count = 5;
+  int *count_p = &count;
+
+  // Add some metadata in the top byte (this will crash unless the
+  // test is running with TBI enabled, but we won't dereference it)
+
+  intptr_t scratch = (intptr_t)count_p;
+  scratch |= (3ULL << 60);
+  int *count_invalid_p = (int *)scratch;
+
+  int (*main_p)() = main;
+  scratch = (intptr_t)main_p;
+  scratch |= (3ULL << 60);
+  int (*main_invalid_p)() = (int (*)())scratch;
+
+  int *global_p = &global;
+  scratch = (intptr_t)global_p;
+  scratch |= (3ULL << 60);
+  int *global_invalid_p = (int *)scratch;
+
+  return count; // break here
+}