Add SBValue::GetValueAsAddress API for removing non-addressing metadata

On target where metadata is stored in bits that aren't used for
virtual addressing -- AArch64 Top Byte Ignore and pointer authentication
are two examples -- an SBValue object representing a pointer will
return the address with metadata for SBValue::GetValueAsUnsigned.
Users may want to get the virtual address without the metadata;
this new method gives them a way to do this.

Differential Revision: https://reviews.llvm.org/D142792

Author: jasonmolenda

lldb/bindings/interface/SBValueDocstrings.i

@@ -135,6 +135,24 @@ 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

@@ -62,6 +62,8 @@ 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/include/lldb/Core/ValueObject.h

@@ -564,6 +564,10 @@ class ValueObject {
 
   lldb::addr_t GetPointerValue(AddressType *address_type = nullptr);
 
+  /// Remove TBI/MTE/ptrauth bits from address, if those are defined on this
+  /// target/ABI.
+  lldb::addr_t GetStrippedPointerValue(lldb::addr_t address);
+
   lldb::ValueObjectSP GetSyntheticChild(ConstString key) const;
 
   lldb::ValueObjectSP GetSyntheticArrayMember(size_t index, bool can_create);

lldb/source/API/SBValue.cpp

@@ -30,6 +30,7 @@
 #include "lldb/Symbol/Type.h"
 #include "lldb/Symbol/Variable.h"
 #include "lldb/Symbol/VariableList.h"
+#include "lldb/Target/ABI.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/StackFrame.h"
@@ -924,6 +925,25 @@ 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;
+    if (ProcessSP process_sp = m_opaque_sp->GetProcessSP())
+      if (ABISP abi_sp = process_sp->GetABI())
+        return abi_sp->FixCodeAddress(ret_val);
+    return ret_val;
+  }
+
+  return fail_value;
+}
+
 bool SBValue::MightHaveChildren() {
   LLDB_INSTRUMENT_VA(this);
 

lldb/source/Core/ValueObject.cpp

@@ -31,6 +31,7 @@
 #include "lldb/Symbol/SymbolContext.h"
 #include "lldb/Symbol/Type.h"
 #include "lldb/Symbol/Variable.h"
+#include "lldb/Target/ABI.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Language.h"
 #include "lldb/Target/LanguageRuntime.h"
@@ -1453,6 +1454,14 @@ addr_t ValueObject::GetAddressOf(bool scalar_is_load_address,
   return LLDB_INVALID_ADDRESS;
 }
 
+addr_t ValueObject::GetStrippedPointerValue(addr_t address) {
+  ExecutionContext exe_ctx(GetExecutionContextRef());
+  if (Process *process = exe_ctx.GetProcessPtr())
+    if (ABISP abi_sp = process->GetABI())
+      return abi_sp->FixCodeAddress(address);
+  return address;
+}
+
 addr_t ValueObject::GetPointerValue(AddressType *address_type) {
   addr_t address = LLDB_INVALID_ADDRESS;
   if (address_type)
@@ -1468,11 +1477,15 @@ addr_t ValueObject::GetPointerValue(AddressType *address_type) {
     address = m_value.GetScalar().ULongLong(LLDB_INVALID_ADDRESS);
     break;
 
-  case Value::ValueType::HostAddress:
+  case Value::ValueType::HostAddress: {
+    lldb::offset_t data_offset = 0;
+    address = m_data.GetAddress(&data_offset);
+  } break;
+
   case Value::ValueType::LoadAddress:
   case Value::ValueType::FileAddress: {
     lldb::offset_t data_offset = 0;
-    address = m_data.GetAddress(&data_offset);
+    address = GetStrippedPointerValue(m_data.GetAddress(&data_offset));
   } break;
   }
 
@@ -3011,6 +3024,11 @@ lldb::ValueObjectSP ValueObject::CreateValueObjectFromAddress(
   if (type) {
     CompilerType pointer_type(type.GetPointerType());
     if (pointer_type) {
+      if (Process *process = exe_ctx.GetProcessPtr()) {
+        if (ABISP abi_sp = process->GetABI()) {
+          address = abi_sp->FixCodeAddress(address);
+        }
+      }
       lldb::DataBufferSP buffer(
           new lldb_private::DataBufferHeap(&address, sizeof(lldb::addr_t)));
       lldb::ValueObjectSP ptr_result_valobj_sp(ValueObjectConstResult::Create(

lldb/source/DataFormatters/ValueObjectPrinter.cpp

@@ -440,6 +440,13 @@ bool ValueObjectPrinter::PrintValueAndSummaryIfNeeded(bool &value_printed,
           if (!m_options.m_hide_name)
             m_stream->PutChar(' ');
           m_stream->PutCString(m_value);
+          if (IsPointerValue(m_valobj->GetCompilerType())) {
+            uint64_t orig_value = m_valobj->GetValueAsUnsigned(0);
+            addr_t stripped = m_valobj->GetPointerValue();
+            if (stripped != orig_value) {
+              m_stream->Printf(" (actual=0x%" PRIx64 ")", stripped);
+            }
+          }
           value_printed = true;
         }
       }

lldb/test/API/api/clear-sbvalue-nonadressable-bits/Makefile

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

lldb/test/API/api/clear-sbvalue-nonadressable-bits/TestClearSBValueNonAddressableBits.py

@@ -0,0 +1,58 @@
+"""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())
+        strm = lldb.SBStream()
+        count_invalid_p.GetDescription(strm)
+        self.assertIn("actual=0x", strm.GetData())
+
+        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())
+        strm = lldb.SBStream()
+        global_invalid_p.GetDescription(strm)
+        self.assertIn("actual=0x", strm.GetData())
+
+        main_p = frame.FindVariable("main_p")
+        main_invalid_p = frame.FindVariable("main_invalid_p")
+        self.assertEqual(main_p.GetValueAsUnsigned(), main_invalid_p.GetValueAsAddress())
+        strm = lldb.SBStream()
+        main_invalid_p.GetDescription(strm)
+        self.assertIn("main at main.c:", strm.GetData())
+        self.assertIn("actual=0x", strm.GetData())

lldb/test/API/api/clear-sbvalue-nonadressable-bits/main.c

@@ -0,0 +1,25 @@
+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
+}