[ubsan] runtime support for pointer overflow checking

[regehr]

Summary

This is the runtime support for this cfe patch to support pointer overflow checking:

http://reviews.llvm.org/D20322

[filcab]

LGTM with the test fix.

test/ubsan/TestCases/Pointer/index-overflow.cpp

20

Something happened here... :-)

[dtzWill]

Hmm, this test actually is wonky if argv[0] happens to be negative when represented as intptr_t... which happens on -m32 for my machine. I'll see about constructing a better test case!

Doing this in a 'portable' manner is amusingly challenging...

[dtzWill]

Fixed test:

// RUN: %clangxx -fsanitize=pointer-overflow %s -o %t
// RUN: %t 1 2>&1 | FileCheck %s --check-prefix=ERR
// RUN: %t 0 2>&1 | FileCheck %s --check-prefix=SAFE
// RUN: %t -1 2>&1 | FileCheck %s --check-prefix=SAFE

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
  // SAFE-NOT: runtime error
  // ERR: runtime error: pointer index expression with base {{.*}} overflowed to

  char *p = (char *)(UINTPTR_MAX);

  printf("%p\n", p + atoi(argv[1]));

  return 0;
}

I'm not sure how to update the revision, but this test should do the trick :).

[regehr]

Fix borked test. Thanks folks!

[Eugene.Zelenko]

Looks like patch was not committed.

lib/ubsan/ubsan_checks.inc

 
 UBSAN_CHECK(GenericUB, "undefined-behavior", "undefined")
 UBSAN_CHECK(NullPointerUse, "null-pointer-use", "null")
+UBSAN_CHECK(PointerOverflow, "pointer-overflow", "pointer-overflow")
 UBSAN_CHECK(MisalignedPointerUse, "misaligned-pointer-use", "alignment")
 UBSAN_CHECK(InsufficientObjectSize, "insufficient-object-size", "object-size")
 UBSAN_CHECK(SignedIntegerOverflow, "signed-integer-overflow",

lib/ubsan/ubsan_handlers.h

 /// \brief Handle passing null pointer to function with nonnull attribute.
 RECOVERABLE(nonnull_arg, NonNullArgData *Data)
 
+struct PointerOverflowData {
+  SourceLocation Loc;
+};
+
+RECOVERABLE(pointer_overflow, PointerOverflowData *Data, ValueHandle Base,
+            ValueHandle Result)
+
 /// \brief Known CFI check kinds.
 /// Keep in sync with the enum of the same name in CodeGenFunction.h
 enum CFITypeCheckKind : unsigned char {

lib/ubsan/ubsan_handlers.cc

   Die();
 }
 
+static void handlePointerOverflowImpl(PointerOverflowData *Data,
+                                      ValueHandle Base,
+                                      ValueHandle Result,
+                                      ReportOptions Opts) {
+  SourceLocation Loc = Data->Loc.acquire();
+  ErrorType ET = ErrorType::PointerOverflow;
+
+  if (ignoreReport(Loc, Opts, ET))
+    return;
+
+  ScopedReport R(Opts, Loc, ET);
+
+  Diag(Loc, DL_Error, "pointer index expression with base %0 overflowed to %1")
+    << (void *)Base << (void*)Result;
+}
+
+void __ubsan::__ubsan_handle_pointer_overflow(PointerOverflowData *Data,
+                                              ValueHandle Base,
+                                              ValueHandle Result) {
+  GET_REPORT_OPTIONS(false);
+  handlePointerOverflowImpl(Data, Base, Result, Opts);
+}
+
+void __ubsan::__ubsan_handle_pointer_overflow_abort(PointerOverflowData *Data,
+                                                    ValueHandle Base,
+                                                    ValueHandle Result) {
+  GET_REPORT_OPTIONS(true);
+  handlePointerOverflowImpl(Data, Base, Result, Opts);
+  Die();
+}
+
 static void handleCFIBadIcall(CFICheckFailData *Data, ValueHandle Function,
                               ReportOptions Opts) {
   if (Data->CheckKind != CFITCK_ICall)

test/ubsan/TestCases/Pointer/index-overflow.cpp

+// RUN: %clangxx -fsanitize=pointer-overflow %s -o %t
+// RUN: %t 1 2>&1 | FileCheck %s --check-prefix=ERR
+// RUN: %t 0 2>&1 | FileCheck %s --check-prefix=SAFE
+// RUN: %t -1 2>&1 | FileCheck %s --check-prefix=SAFE
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+  // SAFE-NOT: runtime error
+  // ERR: runtime error: pointer index expression with base {{.*}} overflowed to
+
+  char *p = (char *)(UINTPTR_MAX);
+
+  printf("%p\n", p + atoi(argv[1]));
+
+  return 0;
+}