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

[Matthew Malcomson via Phabricator via llvm-commits]

mmalcomson updated this revision to Diff 225002.
mmalcomson added a comment.

In D68794#1706679 <https://reviews.llvm.org/D68794#1706679>, @eugenis wrote:

> In D68794#1705862 <https://reviews.llvm.org/D68794#1705862>, @mmalcomson wrote:
>
> > 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)
>
>
> This is a good point. It appears that PR_GET_TAGGED_ADDR_CTRL works even when abi.tagged_addr_disabled=1, we can use it to tell these two cases apart


Ah! So it does!
I'd apparently not updated my kernel since this was added -- thanks for the catch!

I've used that to add a slightly nicer error message and implemented the suggested changes.


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 +34,8 @@
 #include <sys/time.h>
 #include <unistd.h>
 #include <unwind.h>
+#include <sys/prctl.h>
+#include <errno.h>
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_procmaps.h"
@@ -144,6 +146,42 @@
       FindDynamicShadowStart(shadow_size_bytes);
 }
 
+void InitPrctl() {
+#define PR_SET_TAGGED_ADDR_CTRL        55
+#define PR_GET_TAGGED_ADDR_CTRL        56
+#define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
+
+  // Check we're running on a kernel that can use the tagged address ABI.
+  if (internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0) == -1
+      && errno == EINVAL) {
+#if SANITIZER_ANDROID
+    // Some older Android kernels have the tagged pointer ABI on
+    // unconditionally, and hence don't have the tagged-addr prctl while still
+    // allow the ABI.
+    // If targeting Android and the prctl is not around we assume this is the
+    // case.
+    return;
+#else
+    Printf("FATAL: "
+           "HWAddressSanitizer requires a kernel with tagged address ABI.\n");
+    Die();
+#endif
+  }
+
+  // Turn on the tagged address ABI.
+  if (internal_prctl(PR_SET_TAGGED_ADDR_CTRL,
+                     PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == -1
+      || ! internal_prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)) {
+    Printf("FATAL: HWAddressSanitizer failed to enable tagged address "
+           "syscall ABI.\n"
+           "Suggest check `sysctl abi.tagged_addr_disabled` configuration.\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
@@ -312,6 +312,8 @@
 static void InitInstrumentation() {
   if (hwasan_instrumentation_inited) return;
 
+  InitPrctl();
+
   if (!InitShadow()) {
     Printf("FATAL: HWAddressSanitizer cannot mmap the shadow memory.\n");
     DumpProcessMap();


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