Add support for PR_{GET,SET}_TAGGED_ADDR_CTRL prctls

Author: pcc

CMakeLists.txt

@@ -1404,6 +1404,7 @@ set(BASIC_TESTS
   x86/sysfs
   sysinfo
   syslog
+  arm/tagged_addr_ctrl
   tgkill
   thread_yield
   timer

src/record_syscall.cc

@@ -4736,6 +4736,23 @@ static Switchable rec_prepare_syscall_arch(RecordTask* t,
         case PR_SET_THP_DISABLE:
         case PR_SET_SECUREBITS:
         case PR_GET_SECUREBITS:
+        case PR_GET_TAGGED_ADDR_CTRL:
+          break;
+
+        case PR_SET_TAGGED_ADDR_CTRL:
+          if (regs.arg2() & ~PR_TAGGED_ADDR_ENABLE) {
+            // For now we only support enabling the tagged address ABI which
+            // only affects the semantics of syscalls. We don't support setting
+            // any of the MTE-related bits because they affect the semantics of
+            // normal load/store instructions (implying replay is required) as
+            // well as exposing non-determinism in the following ways:
+            // 1) With a non-empty tag inclusion mask, the tag computed by the
+            //    IRG instruction will be effectively random.
+            // 2) It is indeterminate when a SIGSEGV/SEGV_MTEAERR signal will
+            //    be raised if an asynchronous tag check fault is taken.
+            // Both of these issues should be fixable with some kernel changes.
+            syscall_state.emulate_result(-EINVAL);
+          }
           break;
 
         case PR_SET_DUMPABLE:

src/test/arm/tagged_addr_ctrl.c

@@ -0,0 +1,28 @@
+#include "util.h"
+
+#include <linux/prctl.h>
+#include <sys/prctl.h>
+#include <errno.h>
+
+int main(void) {
+  int ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+  // Skip the test on pre-5.4 kernels which predate the prctl.
+  if (ret == -1 && errno == EINVAL) {
+    atomic_puts("EXIT-SUCCESS");
+    return 0;
+  }
+  test_assert(ret == 0);
+
+  ret = prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0);
+  test_assert(ret == 0);
+
+  ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+  test_assert(ret == PR_TAGGED_ADDR_ENABLE);
+
+  // We don't support MTE yet.
+  ret = prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_ASYNC,
+              0, 0, 0);
+  test_assert(ret == -1 && errno == EINVAL);
+
+  atomic_puts("EXIT-SUCCESS");
+}