[PATCH] D56941: MemoryBlock: Do not automatically extend a given size to a multiple of page size.

[Rui Ueyama via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL351916: MemoryBlock: Do not automatically extend a given size to a multiple of page… (authored by ruiu, committed by ).
Herald added a subscriber: kristina.

Changed prior to commit:
  https://reviews.llvm.org/D56941?vs=182973&id=183007#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56941/new/

https://reviews.llvm.org/D56941

Files:
  lld/trunk/test/ELF/stdout.s
  llvm/trunk/lib/ExecutionEngine/SectionMemoryManager.cpp
  llvm/trunk/lib/Support/Unix/Memory.inc


Index: lld/trunk/test/ELF/stdout.s
===================================================================
--- lld/trunk/test/ELF/stdout.s
+++ lld/trunk/test/ELF/stdout.s
@@ -1,12 +1,15 @@
 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
-# RUN: ld.lld %t.o -o - > %t
-# RUN: llvm-objdump -d %t | FileCheck %s
+# RUN: ld.lld %t.o -o - > %t1
+# RUN: llvm-objdump -d %t1 | FileCheck %s
 
 # CHECK: 0000000000201000 _start:
 # CHECK: 201000: 90 nop
 
+# RUN: ld.lld %t.o -o %t2
+# RUN: diff %t1 %t2
+
 .globl _start
 _start:
   nop
Index: llvm/trunk/lib/Support/Unix/Memory.inc
===================================================================
--- llvm/trunk/lib/Support/Unix/Memory.inc
+++ llvm/trunk/lib/Support/Unix/Memory.inc
@@ -91,9 +91,6 @@
   if (NumBytes == 0)
     return MemoryBlock();
 
-  static const size_t PageSize = Process::getPageSize();
-  const size_t NumPages = (NumBytes+PageSize-1)/PageSize;
-
   int fd = -1;
 
   int MMFlags = MAP_PRIVATE |
@@ -113,11 +110,12 @@
   // Use any near hint and the page size to set a page-aligned starting address
   uintptr_t Start = NearBlock ? reinterpret_cast<uintptr_t>(NearBlock->base()) +
                                       NearBlock->size() : 0;
+  static const size_t PageSize = Process::getPageSize();
   if (Start && Start % PageSize)
     Start += PageSize - Start % PageSize;
 
-  void *Addr = ::mmap(reinterpret_cast<void*>(Start), PageSize*NumPages,
-                      Protect, MMFlags, fd, 0);
+  void *Addr = ::mmap(reinterpret_cast<void *>(Start), NumBytes, Protect,
+                      MMFlags, fd, 0);
   if (Addr == MAP_FAILED) {
     if (NearBlock) //Try again without a near hint
       return allocateMappedMemory(NumBytes, nullptr, PFlags, EC);
@@ -128,7 +126,7 @@
 
   MemoryBlock Result;
   Result.Address = Addr;
-  Result.Size = NumPages*PageSize;
+  Result.Size = NumBytes;
 
   // Rely on protectMappedMemory to invalidate instruction cache.
   if (PFlags & MF_EXEC) {
Index: llvm/trunk/lib/ExecutionEngine/SectionMemoryManager.cpp
===================================================================
--- llvm/trunk/lib/ExecutionEngine/SectionMemoryManager.cpp
+++ llvm/trunk/lib/ExecutionEngine/SectionMemoryManager.cpp
@@ -242,7 +242,11 @@
   allocateMappedMemory(SectionMemoryManager::AllocationPurpose Purpose,
                        size_t NumBytes, const sys::MemoryBlock *const NearBlock,
                        unsigned Flags, std::error_code &EC) override {
-    return sys::Memory::allocateMappedMemory(NumBytes, NearBlock, Flags, EC);
+    // allocateMappedMemory calls mmap(2). We round up a request size
+    // to page size to get extra space for free.
+    static const size_t PageSize = sys::Process::getPageSize();
+    size_t ReqBytes = (NumBytes + PageSize - 1) & ~(PageSize - 1);
+    return sys::Memory::allocateMappedMemory(ReqBytes, NearBlock, Flags, EC);
   }
 
   std::error_code protectMappedMemory(const sys::MemoryBlock &Block,


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