jasonmolenda created this revision.
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Herald added a subscriber: lldb-commits.
This patch adds a new method to SBValue, `GetValueAsAddress()`, which will take
the uint64_t value in the SBValue and run it through the ABI's FixAddress
method to clear any TBI/MTE/ptrauth bits on AArch64 targets. Script authors
may want access to both the actual uint64_t value, and the address that will be
accessed, in an SBValue, so I added a new method in addition to
GetValueAsUnsigned to provide this.
I currently have SBValue::GetValueAsAddress NOT perform a type check, and
possibly I should have it check the type's IsPointerType() before doing this,
but at the same time if the script/driver is calling this method, it's probably
best to just do that.
There's also changes to methods like
`ValueObject::CreateValueObjectFromAddress` so we can get SBValue::Dereference
and such to behave correct when you have an SBValue created from a signed
pointer.
I have the attached test case set to run on any AArch64 system; on Darwin we do
the same pointer stripping on any process regardless if it is using pointer
auth (that is, for both "arm64" and "arm64e"). On Linux, a non-ptrauth process
may not have an address mask and this test may fail because the bits I mask
into the top nibble in the test program are not removed by GetValueAsAddress().
I'm not sure exactly, but I can remove this test from running on Linux, or add
a check for `isAArch64PAuth` or something. This program never actually
dereferences this pointer value with bits in the high nibble set, it's only set
up for lldb to manipulate.
We've used this API inside Apple for a bit and it has worked well for our API
users; of course if there is consensus that it should be done differently we'll
find a way to handle that internally.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D142792
Files:
lldb/bindings/interface/SBValue.i
lldb/include/lldb/API/SBValue.h
lldb/include/lldb/Core/ValueObject.h
lldb/source/API/SBValue.cpp
lldb/source/Core/ValueObject.cpp
lldb/source/DataFormatters/ValueObjectPrinter.cpp
lldb/test/API/api/clear-sbvalue-nonadressable-bits/Makefile
lldb/test/API/api/clear-sbvalue-nonadressable-bits/TestClearSBValueNonAddressableBits.py
lldb/test/API/api/clear-sbvalue-nonadressable-bits/main.c
Index: lldb/test/API/api/clear-sbvalue-nonadressable-bits/main.c
===================================================================
--- /dev/null
+++ lldb/test/API/api/clear-sbvalue-nonadressable-bits/main.c
@@ -0,0 +1,15 @@
+#include <stdint.h>
+int main()
+{
+ int v = 5;
+ int *v_p = &v;
+
+ // 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) v_p;
+ scratch |= (3ULL << 60);
+ int *v_invalid_p = (int *)scratch;
+
+ return v; // break here
+}
Index: lldb/test/API/api/clear-sbvalue-nonadressable-bits/TestClearSBValueNonAddressableBits.py
===================================================================
--- /dev/null
+++ lldb/test/API/api/clear-sbvalue-nonadressable-bits/TestClearSBValueNonAddressableBits.py
@@ -0,0 +1,35 @@
+"""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']))
+
+ 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 ("v v v_p v_invalid_p")
+ self.runCmd ("v &v &v_p &v_invalid_p")
+
+ frame = thread.GetFrameAtIndex(0)
+ v_p = frame.FindVariable("v_p")
+ v_invalid_p = frame.FindVariable("v_invalid_p")
+
+ self.assertEqual(v_p.GetValueAsUnsigned(), v_invalid_p.GetValueAsAddress())
+ self.assertNotEqual(v_invalid_p.GetValueAsUnsigned(), v_invalid_p.GetValueAsAddress())
+
+ self.assertEqual(5, v_p.Dereference().GetValueAsUnsigned())
+ self.assertEqual(5, v_invalid_p.Dereference().GetValueAsUnsigned())
Index: lldb/test/API/api/clear-sbvalue-nonadressable-bits/Makefile
===================================================================
--- /dev/null
+++ lldb/test/API/api/clear-sbvalue-nonadressable-bits/Makefile
@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules
Index: lldb/source/DataFormatters/ValueObjectPrinter.cpp
===================================================================
--- lldb/source/DataFormatters/ValueObjectPrinter.cpp
+++ lldb/source/DataFormatters/ValueObjectPrinter.cpp
@@ -426,6 +426,11 @@
IsPointerValue(m_valobj->GetCompilerType())) {
} else {
m_stream->Printf(" %s", m_value.c_str());
+ addr_t stripped =
+ m_valobj->GetStrippedPointerValue(m_valobj->GetPointerValue());
+ if (stripped != m_valobj->GetPointerValue()) {
+ m_stream->Printf(" (actual=0x%" PRIx64 ")", stripped);
+ }
value_printed = true;
}
}
Index: lldb/source/Core/ValueObject.cpp
===================================================================
--- lldb/source/Core/ValueObject.cpp
+++ 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"
@@ -1442,6 +1443,14 @@
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)
@@ -1461,7 +1470,7 @@
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;
}
@@ -3000,6 +3009,11 @@
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(
Index: lldb/source/API/SBValue.cpp
===================================================================
--- lldb/source/API/SBValue.cpp
+++ 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"
@@ -920,6 +921,29 @@
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;
+ ABISP abi_sp = process_sp->GetABI();
+ if (abi_sp)
+ return abi_sp->FixCodeAddress(ret_val);
+ return ret_val;
+ }
+
+ return fail_value;
+}
+
bool SBValue::MightHaveChildren() {
LLDB_INSTRUMENT_VA(this);
Index: lldb/include/lldb/Core/ValueObject.h
===================================================================
--- lldb/include/lldb/Core/ValueObject.h
+++ lldb/include/lldb/Core/ValueObject.h
@@ -564,6 +564,10 @@
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);
Index: lldb/include/lldb/API/SBValue.h
===================================================================
--- lldb/include/lldb/API/SBValue.h
+++ lldb/include/lldb/API/SBValue.h
@@ -62,6 +62,8 @@
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
Index: lldb/bindings/interface/SBValue.i
===================================================================
--- lldb/bindings/interface/SBValue.i
+++ lldb/bindings/interface/SBValue.i
@@ -113,6 +113,28 @@
uint64_t
GetValueAsUnsigned(uint64_t fail_value=0);
+ %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/TBI/MTE bits.
+ //
+ // Calling this on a random value which is not a pointer is an
+ // 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."
+ ) GetValueAsAddress;
+
+ lldb::addr_t
+ GetValueAsAddress();
+
ValueType
GetValueType ();
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