[PATCH] D68794: libhwasan initialisation include kernel syscall ABI relaxation

[Matthew Malcomson via Phabricator via llvm-commits]

mmalcomson updated this revision to Diff 224582.
mmalcomson edited the summary of this revision.
mmalcomson added a comment.

Run `prctl` syscall for Android, but ignore EINVAL failures.

NOTE: I don't believe this distinguishes between running on a kernel with with the tagged address ABI unconditional or running on a newer kernel or on a kernel with `sysctl abi.tagged_addr_disabled=1`
(https://android.googlesource.com/kernel/common/+/690c4ca8a5715644370384672f24d95b042db74a/Documentation/arm64/tagged-address-abi.rst)

I doubt this will be much of a concern -- there was already a requirement of having the correct Android kernel for things to work -- but am mentioning it for posterity.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68794/new/

https://reviews.llvm.org/D68794

Files:
  compiler-rt/lib/hwasan/hwasan.cpp
  compiler-rt/lib/hwasan/hwasan.h
  compiler-rt/lib/hwasan/hwasan_linux.cpp


Index: compiler-rt/lib/hwasan/hwasan_linux.cpp
===================================================================
--- compiler-rt/lib/hwasan/hwasan_linux.cpp
+++ compiler-rt/lib/hwasan/hwasan_linux.cpp
@@ -34,6 +34,7 @@
 #include <sys/time.h>
 #include <unistd.h>
 #include <unwind.h>
+#include <sys/prctl.h>
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_procmaps.h"
@@ -144,6 +145,33 @@
       FindDynamicShadowStart(shadow_size_bytes);
 }
 
+void InitPrctl() {
+  // This function uses the prctl interface to ask the kernel to accept
+  // tagged pointers.
+  //
+  // Here we unconditionally request that the PR_TAGGED_ADDR_ENABLE value is
+  // turned on, there is nothing else that can be done.
+#define PR_SET_TAGGED_ADDR_CTRL        55
+#define PR_GET_TAGGED_ADDR_CTRL        56
+#define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
+  if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == -1
+      || ! prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)) {
+#if SANITIZER_ANDROID
+    // Some older Android kernels have the tagged pointer ABI on
+    // unconditionally, and hence don't have the tagged-addr prctl.
+    //
+    // In order to handle those we ignore getting EINVAL. */
+    if (errno == EINVAL)
+      return;
+#endif
+    Printf("FATAL: HWAddressSanitizer failed to enable tagged pointer syscall ABI.\n");
+    Die();
+  }
+#undef PR_SET_TAGGED_ADDR_CTRL
+#undef PR_GET_TAGGED_ADDR_CTRL
+#undef PR_TAGGED_ADDR_ENABLE
+}
+
 bool InitShadow() {
   // Define the entire memory range.
   kHighMemEnd = GetHighMemEnd();
Index: compiler-rt/lib/hwasan/hwasan.h
===================================================================
--- compiler-rt/lib/hwasan/hwasan.h
+++ compiler-rt/lib/hwasan/hwasan.h
@@ -74,6 +74,7 @@
 
 bool ProtectRange(uptr beg, uptr end);
 bool InitShadow();
+void InitPrctl();
 void InitThreads();
 void MadviseShadow();
 char *GetProcSelfMaps();
Index: compiler-rt/lib/hwasan/hwasan.cpp
===================================================================
--- compiler-rt/lib/hwasan/hwasan.cpp
+++ compiler-rt/lib/hwasan/hwasan.cpp
@@ -354,6 +354,8 @@
   hwasan_init_is_running = 1;
   SanitizerToolName = "HWAddressSanitizer";
 
+  InitPrctl();
+
   InitTlsSize();
 
   CacheBinaryName();


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