[Lldb-commits] [lldb] [lldb] [Mach-O] ProcessMachCore needs to strip TBI data from addrs (PR #84998)

[Jason Molenda via lldb-commits]

https://github.com/jasonmolenda created https://github.com/llvm/llvm-project/pull/84998

Darwin AArch64 application processors are run with Top Byte Ignore mode enabled so metadata may be stored in the top byte, it needs to be ignored when reading/writing memory.  David Spickett handled this already in the base class Process::ReadMemory but ProcessMachCore overrides that method (to avoid the memory cache) and did not pick up the same change.  I add a test case that creates a pointer with metadata in the top byte and dereferences it with a live process and with a corefile.

rdar://123784501

>From 4278537c262b01b1d6432391bd9d8017eb96c60a Mon Sep 17 00:00:00 2001
From: Jason Molenda <jmolenda at apple.com>
Date: Tue, 12 Mar 2024 17:09:30 -0700
Subject: [PATCH] [lldb] [Mach-O] ProcessMachCore needs to strip TBI data from
 addrs

Darwin AArch64 application processors are run with Top Byte Ignore
mode enabled so metadata may be stored in the top byte, it needs
to be ignored when reading/writing memory.  David Spickett handled
this already in the base class Process::ReadMemory but ProcessMachCore
overrides that method (to avoid the memory cache) and did not pick
up the same change.  I add a test case that creates a pointer with
metadata in the top byte and dereferences it with a live process and
with a corefile.

rdar://123784501
---
 .../Process/mach-core/ProcessMachCore.cpp     |  2 +-
 lldb/test/API/macosx/tbi-honored/Makefile     |  3 ++
 .../API/macosx/tbi-honored/TestTBIHonored.py  | 49 +++++++++++++++++++
 lldb/test/API/macosx/tbi-honored/main.c       | 13 +++++
 4 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 lldb/test/API/macosx/tbi-honored/Makefile
 create mode 100644 lldb/test/API/macosx/tbi-honored/TestTBIHonored.py
 create mode 100644 lldb/test/API/macosx/tbi-honored/main.c

diff --git a/lldb/source/Plugins/Process/mach-core/ProcessMachCore.cpp b/lldb/source/Plugins/Process/mach-core/ProcessMachCore.cpp
index 3961dcf0fbcc0e..7b9938d4f02020 100644
--- a/lldb/source/Plugins/Process/mach-core/ProcessMachCore.cpp
+++ b/lldb/source/Plugins/Process/mach-core/ProcessMachCore.cpp
@@ -652,7 +652,7 @@ size_t ProcessMachCore::ReadMemory(addr_t addr, void *buf, size_t size,
                                    Status &error) {
   // Don't allow the caching that lldb_private::Process::ReadMemory does since
   // in core files we have it all cached our our core file anyway.
-  return DoReadMemory(addr, buf, size, error);
+  return DoReadMemory(FixAnyAddress(addr), buf, size, error);
 }
 
 size_t ProcessMachCore::DoReadMemory(addr_t addr, void *buf, size_t size,
diff --git a/lldb/test/API/macosx/tbi-honored/Makefile b/lldb/test/API/macosx/tbi-honored/Makefile
new file mode 100644
index 00000000000000..10495940055b63
--- /dev/null
+++ b/lldb/test/API/macosx/tbi-honored/Makefile
@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules
diff --git a/lldb/test/API/macosx/tbi-honored/TestTBIHonored.py b/lldb/test/API/macosx/tbi-honored/TestTBIHonored.py
new file mode 100644
index 00000000000000..d38685359af6d1
--- /dev/null
+++ b/lldb/test/API/macosx/tbi-honored/TestTBIHonored.py
@@ -0,0 +1,49 @@
+"""Test that lldb on Darwin ignores metadata in the top byte of addresses."""
+
+import os
+import re
+import subprocess
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestTBIHonored(TestBase):
+    @no_debug_info_test
+    @skipUnlessDarwin
+    @skipIf(archs=no_match(["arm64", "arm64e"]))
+    @skipIfRemote
+    def do_variable_access_tests(self, frame):
+        self.assertEqual(
+            frame.variables["pb"][0]
+            .GetChildMemberWithName("p")
+            .Dereference()
+            .GetValueAsUnsigned(),
+            15,
+        )
+        addr = frame.variables["pb"][0].GetChildMemberWithName("p").GetValueAsUnsigned()
+        self.expect("expr -- *pb.p", substrs=["15"])
+        self.expect("frame variable *pb.p", substrs=["15"])
+        self.expect("expr -- *(int*)0x%x" % addr, substrs=["15"])
+
+    def test(self):
+        corefile = self.getBuildArtifact("process.core")
+        self.build()
+        (target, process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
+            self, "// break here", lldb.SBFileSpec("main.c")
+        )
+
+        self.do_variable_access_tests(thread.GetFrameAtIndex(0))
+
+        self.runCmd("process save-core -s stack " + corefile)
+        self.dbg.DeleteTarget(target)
+
+        # Now load the corefile
+        target = self.dbg.CreateTarget("")
+        process = target.LoadCore(corefile)
+        thread = process.GetSelectedThread()
+        self.assertTrue(process.GetSelectedThread().IsValid())
+
+        self.do_variable_access_tests(thread.GetFrameAtIndex(0))
diff --git a/lldb/test/API/macosx/tbi-honored/main.c b/lldb/test/API/macosx/tbi-honored/main.c
new file mode 100644
index 00000000000000..3d7ad0b04cd664
--- /dev/null
+++ b/lldb/test/API/macosx/tbi-honored/main.c
@@ -0,0 +1,13 @@
+#include <stdint.h>
+#include <stdio.h>
+union ptrbytes {
+  int *p;
+  uint8_t bytes[8];
+};
+int main() {
+  int c = 15;
+  union ptrbytes pb;
+  pb.p = &c;
+  pb.bytes[7] = 0xfe;
+  printf("%d\n", *pb.p); // break here
+}