Release memory to OS only when the requested range covers the entire page

Summary:
The current code was sometimes attempting to release huge chunks of
memory due to undesired RoundUp/RoundDown interaction when the requested
range is fully contained within one memory page.

Reviewers: eugenis

Subscribers: kubabrecka, llvm-commits

Patch by Aleksey Shlyapnikov.

Differential Revision: https://reviews.llvm.org/D27228

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@288271 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/sanitizer_common/sanitizer_common.h b/lib/sanitizer_common/sanitizer_common.h
index 70b10864c..bf66d00d6 100644
--- a/lib/sanitizer_common/sanitizer_common.h
+++ b/lib/sanitizer_common/sanitizer_common.h
@@ -103,7 +103,9 @@ uptr FindAvailableMemoryRange(uptr size, uptr alignment, uptr left_padding);
 
 // Used to check if we can map shadow memory to a fixed location.
 bool MemoryRangeIsAvailable(uptr range_start, uptr range_end);
-void ReleaseMemoryToOS(uptr addr, uptr size);
+// Releases memory pages entirely within the [beg, end] address range. Noop if
+// the provided range does not contain at least one entire page.
+void ReleaseMemoryPagesToOS(uptr beg, uptr end);
 void IncreaseTotalMmap(uptr size);
 void DecreaseTotalMmap(uptr size);
 uptr GetRSS();