Reland "[scudo] Apply filling when realloc shrinks and re-grows a block in-place"

[fabio-d]

Reland of #93212, which has been reverted in
commit bddd8ea.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Fabio D'Urso (fabio-d)

Changes

Reland of #93212, which has been reverted in
commit bddd8ea.

---

Full diff: https://github.com/llvm/llvm-project/pull/95838.diff

2 Files Affected:

• (modified) compiler-rt/lib/scudo/standalone/combined.h (+14)
• (modified) compiler-rt/lib/scudo/standalone/tests/combined_test.cpp (+18-5)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index f9ed36581f8d3..73da686287747 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -565,6 +565,20 @@ class Allocator {
             storeSecondaryAllocationStackMaybe(Options, OldPtr, NewSize);
           }
         }
+
+        // If we have reduced the size, set the extra bytes to the fill value
+        // so that we are ready to grow it again in the future.
+        if (NewSize < OldSize) {
+          const FillContentsMode FillContents =
+              TSDRegistry.getDisableMemInit() ? NoFill
+                                              : Options.getFillContentsMode();
+          if (FillContents != NoFill) {
+            memset(reinterpret_cast<char *>(OldTaggedPtr) + NewSize,
+                   FillContents == ZeroFill ? 0 : PatternFillByte,
+                   OldSize - NewSize);
+          }
+        }
+
         return OldTaggedPtr;
       }
     }
diff --git a/compiler-rt/lib/scudo/standalone/tests/combined_test.cpp b/compiler-rt/lib/scudo/standalone/tests/combined_test.cpp
index 1a36155bcd423..655dc87cbac64 100644
--- a/compiler-rt/lib/scudo/standalone/tests/combined_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/combined_test.cpp
@@ -447,19 +447,32 @@ SCUDO_TYPED_TEST(ScudoCombinedDeathTest, ReallocateSame) {
   // returns the same chunk. This requires that all the sizes we iterate on use
   // the same block size, but that should be the case for MaxSize - 64 with our
   // default class size maps.
-  constexpr scudo::uptr ReallocSize =
+  constexpr scudo::uptr InitialSize =
       TypeParam::Primary::SizeClassMap::MaxSize - 64;
-  void *P = Allocator->allocate(ReallocSize, Origin);
   const char Marker = 'A';
-  memset(P, Marker, ReallocSize);
+  Allocator->setFillContents(scudo::PatternOrZeroFill);
+
+  void *P = Allocator->allocate(InitialSize, Origin);
+  scudo::uptr CurrentSize = InitialSize;
   for (scudo::sptr Delta = -32; Delta < 32; Delta += 8) {
+    memset(P, Marker, CurrentSize);
     const scudo::uptr NewSize =
-        static_cast<scudo::uptr>(static_cast<scudo::sptr>(ReallocSize) + Delta);
+        static_cast<scudo::uptr>(static_cast<scudo::sptr>(InitialSize) + Delta);
     void *NewP = Allocator->reallocate(P, NewSize);
     EXPECT_EQ(NewP, P);
-    for (scudo::uptr I = 0; I < ReallocSize - 32; I++)
+
+    // Verify that existing contents have been preserved.
+    for (scudo::uptr I = 0; I < scudo::Min(CurrentSize, NewSize); I++)
       EXPECT_EQ((reinterpret_cast<char *>(NewP))[I], Marker);
+
+    // Verify that new bytes are set according to FillContentsMode.
+    for (scudo::uptr I = CurrentSize; I < NewSize; I++) {
+      EXPECT_EQ((reinterpret_cast<unsigned char *>(NewP))[I],
+                scudo::PatternFillByte);
+    }
+
     checkMemoryTaggingMaybe(Allocator, NewP, NewSize, 0);
+    CurrentSize = NewSize;
   }
   Allocator->deallocate(P, Origin);
 }

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-cuda-l4 running on cuda-l4-0 while building compiler-rt at step 3 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/101/builds/287

Here is the relevant piece of the build log for the reference:

Step 3 (annotate) failure: '/buildbot/cuda-build --jobs=' (failure)
...
  NV_LIBCUBLAS_PACKAGE_NAME=libcublas-12-2
  NV_LIBCUBLAS_VERSION=12.2.5.6-1
  NV_LIBCUSPARSE_VERSION=12.1.2.141-1
  NV_LIBNCCL_PACKAGE=libnccl2=2.18.5-1+cuda12.2
  NV_LIBNCCL_PACKAGE_NAME=libnccl2
  NV_LIBNCCL_PACKAGE_VERSION=2.18.5-1
  NV_LIBNPP_PACKAGE=libnpp-12-2=12.2.1.4-1
  NV_LIBNPP_VERSION=12.2.1.4-1
  NV_NVTX_VERSION=12.2.140-1
  PATH=/usr/local/nvidia/bin:/usr/local/cuda/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/buildbot
  PWD=/buildbot/cuda-l4-0/work/cuda-l4-0/clang-cuda-l4/build
  SHLVL=1
  TERM=dumb
  WORK_DIR=/buildbot/cuda-l4-0/work
  _=/usr/local/bin/buildbot-worker
 using PTY: False
++ echo @@@HALT_ON_FAILURE@@@
++ readlink -f ..
+ buildbot_dir=/buildbot/cuda-l4-0/work/cuda-l4-0/clang-cuda-l4
+ revision=7fc975aa26f2e0ce6c80629209115ea58b245da5
+ GPU_ARCH=sm_89
+ CUDA_TEST_JOBS=1
+ build_base=/buildbot/cuda-l4-0/work/clang-cuda-l4
+ mkdir -p /buildbot/cuda-l4-0/work/clang-cuda-l4
+ build_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/build
+ libc_build_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/build-libc
+ clang_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/clang
+ testsuite_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/llvm-test-suite
+ llvm_src_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/llvm
+ ext_dir=/buildbot/cuda-l4-0/work/clang-cuda-l4/external
+ inner_pid=669580
+ do_build_and_test
+ trap 'handle_termination $inner_pid' TERM
+ wait 669580
+ fetch_prebuilt_clang 7fc975aa26f2e0ce6c80629209115ea58b245da5 /buildbot/cuda-l4-0/work/clang-cuda-l4/clang
+ local revision=7fc975aa26f2e0ce6c80629209115ea58b245da5
+ local destdir=/buildbot/cuda-l4-0/work/clang-cuda-l4/clang
+ local 'timeout=10 minutes'
++ date -ud '10 minutes' +%s
+ local endtime=1718783272
++ storage_location llvm-7fc975aa26f2e0ce6c80629209115ea58b245da5
++ local file=llvm-7fc975aa26f2e0ce6c80629209115ea58b245da5
++ local default_storage_prefix=gs://cudabot-gce-artifacts/
++ echo gs://cudabot-gce-artifacts/llvm-7fc975aa26f2e0ce6c80629209115ea58b245da5
+ local snapshot=gs://cudabot-gce-artifacts/llvm-7fc975aa26f2e0ce6c80629209115ea58b245da5
+ step 'Waiting for LLVM & Clang snapshot to be built. '
+ local 'name=Waiting for LLVM & Clang snapshot to be built. '
+ local summary=
+ echo '@@@BUILD_STEP Waiting for LLVM & Clang snapshot to be built. @@@'
+ step_summary_clear