[lldb][AArch64][Linux] Show MTE store only setting in mte_ctrl

This controls whether tag checking is performed for loads and
stores, or stores only.

It requires a specific architecture feature which we detect
with a HWCAP3 and cpuinfo feature.

Live process tests look for this and adjust expectations
accordingly, core file tests are using an updated file with
this feature enabled.

The size of the core file has increased and there's nothing
I can do about that. Could be the presence of new architecure
features or kernel changes since I last generated them.

I can generate a smaller file that has the tag segment,
but that segment does not actually contain tag data. So
that's no use.

(and I will fix handling of such files later)

Author: DavidSpickett

lldb/packages/Python/lldbsuite/test/lldbtest.py

@@ -1380,6 +1380,9 @@ def isAArch64SMEFA64(self):
     def isAArch64MTE(self):
         return self.isAArch64() and "mte" in self.getCPUInfo()
 
+    def isAArch64MTEStoreOnly(self):
+        return self.isAArch64() and "mtestoreonly" in self.getCPUInfo()
+
     def isAArch64GCS(self):
         return self.isAArch64() and "gcs" in self.getCPUInfo()
 

lldb/source/Plugins/Process/Utility/RegisterFlagsDetector_arm64.cpp

@@ -26,6 +26,8 @@
 #define HWCAP2_EBF16 (1ULL << 32)
 #define HWCAP2_FPMR (1ULL << 48)
 
+#define HWCAP3_MTE_STORE_ONLY (1ULL << 1)
+
 using namespace lldb_private;
 
 Arm64RegisterFlagsDetector::Fields
@@ -92,7 +94,6 @@ Arm64RegisterFlagsDetector::Fields
 Arm64RegisterFlagsDetector::DetectMTECtrlFields(uint64_t hwcap, uint64_t hwcap2,
                                                 uint64_t hwcap3) {
   (void)hwcap;
-  (void)hwcap3;
 
   if (!(hwcap2 & HWCAP2_MTE))
     return {};
@@ -104,9 +105,18 @@ Arm64RegisterFlagsDetector::DetectMTECtrlFields(uint64_t hwcap, uint64_t hwcap2,
   static const FieldEnum tcf_enum(
       "tcf_enum",
       {{0, "TCF_NONE"}, {1, "TCF_SYNC"}, {2, "TCF_ASYNC"}, {3, "TCF_ASYMM"}});
-  return {{"TAGS", 3, 18}, // 16 bit bitfield shifted up by PR_MTE_TAG_SHIFT.
-          {"TCF", 1, 2, &tcf_enum},
-          {"TAGGED_ADDR_ENABLE", 0}};
+
+  std::vector<RegisterFlags::Field> fields;
+  fields.reserve(5);
+  if (hwcap3 & HWCAP3_MTE_STORE_ONLY)
+    fields.push_back({"STORE_ONLY", 19});
+  fields.insert(
+      std::end(fields),
+      {{"TAGS", 3, 18}, // 16 bit bitfield shifted up by PR_MTE_TAG_SHIFT.
+       {"TCF", 1, 2, &tcf_enum},
+       {"TAGGED_ADDR_ENABLE", 0}});
+
+  return fields;
 }
 
 Arm64RegisterFlagsDetector::Fields

lldb/test/API/commands/register/register/aarch64_mte_ctrl_register/TestMTECtrlRegister.py

@@ -34,29 +34,41 @@ def test_mte_ctrl_register(self):
             substrs=["stop reason = breakpoint 1."],
         )
 
-        def check_mte_ctrl(async_err, sync_err):
+        has_store_only = self.isAArch64MTEStoreOnly()
+
+        def check_mte_ctrl(async_err, sync_err, store_only):
             # Bit 0 = tagged addressing enabled
             # Bit 1 = synchronous faults
             # Bit 2 = asynchronous faults
-            value = "0x{:016x}".format((async_err << 2) | (sync_err << 1) | 1)
+            # Bit 19 = store only checking mode
+            value = "0x{:016x}".format(
+                (store_only << 19) | (async_err << 2) | (sync_err << 1) | 1
+            )
             expected = [value]
 
             if self.hasXMLSupport():
+                fields = "("
+                if has_store_only:
+                    fields += f"STORE_ONLY = {store_only}, "
+
                 tfc_modes = ["NONE", "SYNC", "ASYNC", "ASYMM"]
-                expected.append(
-                    f"(TAGS = 0, TCF = TCF_{tfc_modes[async_err << 1 | sync_err]}, TAGGED_ADDR_ENABLE = 1)".format(
-                        async_err, sync_err
-                    )
-                )
+                fields += f"TAGS = 0, TCF = TCF_{tfc_modes[async_err << 1 | sync_err]}, TAGGED_ADDR_ENABLE = 1)"
+
+                expected.append(fields)
 
             self.expect("register read mte_ctrl", substrs=expected)
 
         # We start enabled with synchronous faults.
-        check_mte_ctrl(0, 1)
+        check_mte_ctrl(0, 1, 0)
         # Change to asynchronous faults.
         self.runCmd("register write mte_ctrl 5")
-        check_mte_ctrl(1, 0)
+        check_mte_ctrl(1, 0, 0)
         # This would return to synchronous faults if we did not restore the
         # previous value.
         self.expect("expression setup_mte()", substrs=["= 0"])
-        check_mte_ctrl(1, 0)
+        check_mte_ctrl(1, 0, 0)
+
+        # Store only checking requires FEAT_MTE_STORE_ONLY.
+        if has_store_only:
+            self.runCmd(f"register write mte_ctrl {1 | (1 << 19)}")
+            check_mte_ctrl(0, 0, 1)

lldb/test/API/linux/aarch64/mte_core_file/TestAArch64LinuxMTEMemoryTagCoreFile.py

@@ -10,8 +10,8 @@
 class AArch64LinuxMTEMemoryTagCoreFileTestCase(TestBase):
     NO_DEBUG_INFO_TESTCASE = True
 
-    MTE_BUF_ADDR = hex(0xFFFF82C74000)
-    BUF_ADDR = hex(0xFFFF82C73000)
+    MTE_BUF_ADDR = hex(0xFFFFA733B000)
+    BUF_ADDR = hex(0xFFFFA733A000)
 
     @skipIfLLVMTargetMissing("AArch64")
     def test_mte_tag_core_file_memory_region(self):
@@ -215,7 +215,7 @@ def test_mte_tag_fault_reason(self):
         self.expect(
             "bt",
             substrs=[
-                "* thread #1, name = 'a.out.mte', stop reason = SIGSEGV: sync tag check fault (fault address=0xffff82c74010)"
+                "* thread #1, name = 'a.out.mte', stop reason = SIGSEGV: sync tag check fault (fault address=0xffffa733b010)"
             ],
         )
 
@@ -231,12 +231,15 @@ def test_mte_ctrl_register(self):
         self.runCmd("target create --core core.mte")
         # The expected value is:
         # * Allowed tags value of 0xFFFF, shifted up by 3 resulting in 0x7fff8.
+        # * Bit 19 set to 0, which means that store only checking is disabled.
         # * Bit 1 set to enable synchronous tag faults.
         # * Bit 0 set to enable the tagged address ABI.
         expected = ["mte_ctrl = 0x000000000007fffb"]
 
         if self.hasXMLSupport():
-            expected.append("(TAGS = 65535, TCF = TCF_SYNC, TAGGED_ADDR_ENABLE = 1)")
+            expected.append(
+                "(STORE_ONLY = 0, TAGS = 65535, TCF = TCF_SYNC, TAGGED_ADDR_ENABLE = 1)"
+            )
 
         self.expect("register read mte_ctrl", substrs=expected)
 

lldb/test/API/linux/aarch64/mte_core_file/core.mte

@@ -23,7 +23,7 @@
 
 int main(int argc, char const *argv[]) {
 #ifdef NO_MTE
-  *(char *)(0) = 0;
+  __builtin_trap();
 #endif
 
   if (prctl(PR_SET_TAGGED_ADDR_CTRL,