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Commit abc2c3ab authored by Peter Collingbourne's avatar Peter Collingbourne
Browse files

Change the android_mallopt(M_SET_HEAP_TAGGING_LEVEL) API. 

- Make it apply to every thread, and thus remove the restriction
  that it must be called while the program is single threaded.
- Make it change TCF0 itself (on all threads), instead of requiring
  callers to do it themselves, which can be error prone.

And update all of the call sites.

Change the implementation of
android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) to call
android_mallopt(M_SET_HEAP_TAGGING_LEVEL) internally. This avoids
crashes during startup that were observed when the two mallopts
updated TCF0 unaware of each other.

I wouldn't expect there to be any out-of-tree callers at this point,
but it's worth noting that the new interface is backwards compatible
with the old one because it strictly expands the set of situations in
which the API can be used (i.e. situations where there are multiple
threads running or where TCF0 hadn't been updated beforehand).

Bug: 135772972
Change-Id: I7746707898ff31ef2e0af01c4f55ba90b72bef51
parent dd1a0165

core/jni/com_android_internal_os_Zygote.cpp

+1 −32
Original line number Diff line number Diff line
@@ -78,7 +78,6 @@ 
#include <android-base/unique_fd.h>

#include <bionic/malloc.h>

#include <bionic/mte.h>

#include <bionic/mte_kernel.h>

#include <cutils/fs.h>

#include <cutils/memory.h>

#include <cutils/multiuser.h>
@@ -1676,28 +1675,6 @@ static void BindMountStorageDirs(JNIEnv* env, jobjectArray pkg_data_info_list, 
  }

}



#ifdef ANDROID_EXPERIMENTAL_MTE

static void SetTagCheckingLevel(int level) {

#ifdef __aarch64__

  if (!(getauxval(AT_HWCAP2) & HWCAP2_MTE)) {

    return;

  }



  int tagged_addr_ctrl = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);

  if (tagged_addr_ctrl < 0) {

    ALOGE("prctl(PR_GET_TAGGED_ADDR_CTRL) failed: %s", strerror(errno));

    return;

  }



  tagged_addr_ctrl = (tagged_addr_ctrl & ~PR_MTE_TCF_MASK) | level;

  if (prctl(PR_SET_TAGGED_ADDR_CTRL, tagged_addr_ctrl, 0, 0, 0) < 0) {

    ALOGE("prctl(PR_SET_TAGGED_ADDR_CTRL, %d) failed: %s", tagged_addr_ctrl,

          strerror(errno));

  }

#endif

}

#endif



// Utility routine to specialize a zygote child process.

static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,

                             jint runtime_flags, jobjectArray rlimits,
@@ -1833,22 +1810,14 @@ static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids, 
      heap_tagging_level = M_HEAP_TAGGING_LEVEL_TBI;

      break;

    case RuntimeFlags::MEMORY_TAG_LEVEL_ASYNC:

#ifdef ANDROID_EXPERIMENTAL_MTE

      SetTagCheckingLevel(PR_MTE_TCF_ASYNC);

#endif

      heap_tagging_level = M_HEAP_TAGGING_LEVEL_ASYNC;

      break;

    case RuntimeFlags::MEMORY_TAG_LEVEL_SYNC:

#ifdef ANDROID_EXPERIMENTAL_MTE

      SetTagCheckingLevel(PR_MTE_TCF_SYNC);

#endif

      heap_tagging_level = M_HEAP_TAGGING_LEVEL_SYNC;

      break;

    default:

#ifdef ANDROID_EXPERIMENTAL_MTE

      SetTagCheckingLevel(PR_MTE_TCF_NONE);

#endif

      heap_tagging_level = M_HEAP_TAGGING_LEVEL_NONE;

      break;

  }

  android_mallopt(M_SET_HEAP_TAGGING_LEVEL, &heap_tagging_level, sizeof(heap_tagging_level));

  // Now that we've used the flag, clear it so that we don't pass unknown flags to the ART runtime.