(Wangle) Possibly undefined behavior in collect

[folly.git] / folly / MemoryMapping.cpp

diff --git a/folly/MemoryMapping.cpp b/folly/MemoryMapping.cpp
index 4e78b560d9228d1c3f9eb608b86ffec9863d9b11..35c8eda69db9f424f3b0e3ce247629055a7f7ed6 100644 (file)
--- a/folly/MemoryMapping.cpp
+++ b/folly/MemoryMapping.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2015 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,8 +15,12 @@
  */
 
 #include <folly/MemoryMapping.h>
+
+#include <algorithm>
+#include <functional>
+#include <utility>
+
 #include <folly/Format.h>
-#include <folly/Portability.h>
 
 #ifdef __linux__
 #include <folly/experimental/io/HugePages.h>
@@ -38,7 +42,7 @@ DEFINE_int64(mlock_chunk_size, 1 << 20,  // 1MB
 
 namespace folly {
 
-MemoryMapping::MemoryMapping(MemoryMapping&& other) {
+MemoryMapping::MemoryMapping(MemoryMapping&& other) noexcept {
   swap(other);
 }
 
@@ -52,7 +56,10 @@ MemoryMapping::MemoryMapping(File file, off_t offset, off_t length,
 
 MemoryMapping::MemoryMapping(const char* name, off_t offset, off_t length,
                              Options options)
-  : MemoryMapping(File(name), offset, length, options) { }
+    : MemoryMapping(File(name, options.writable ? O_RDWR : O_RDONLY),
+                    offset,
+                    length,
+                    options) { }
 
 MemoryMapping::MemoryMapping(int fd, off_t offset, off_t length,
                              Options options)
@@ -237,9 +244,8 @@ bool MemoryMapping::mlock(LockMode lock) {
     return true;
   }
 
-  auto msg(folly::format(
-    "mlock({}) failed at {}",
-    mapLength_, amountSucceeded).str());
+  auto msg =
+    folly::sformat("mlock({}) failed at {}", mapLength_, amountSucceeded);
 
   if (lock == LockMode::TRY_LOCK && (errno == EPERM || errno == ENOMEM)) {
     PLOG(WARNING) << msg;
@@ -280,17 +286,36 @@ MemoryMapping::~MemoryMapping() {
     size_t amountSucceeded = 0;
     if (!memOpInChunks(::munmap, mapStart_, mapLength_, options_.pageSize,
                        amountSucceeded)) {
-      PLOG(FATAL) << folly::format(
-        "munmap({}) failed at {}",
-        mapLength_, amountSucceeded).str();
+      PLOG(FATAL) << folly::format("munmap({}) failed at {}",
+                                   mapLength_, amountSucceeded);
     }
   }
 }
 
-void MemoryMapping::advise(int advice) const {
-  if (mapLength_ && ::madvise(mapStart_, mapLength_, advice)) {
-    PLOG(WARNING) << "madvise()";
+void MemoryMapping::advise(int advice) const { advise(advice, 0, mapLength_); }
+
+void MemoryMapping::advise(int advice, size_t offset, size_t length) const {
+  CHECK_LE(offset + length, mapLength_)
+    << " offset: " << offset
+    << " length: " << length
+    << " mapLength_: " << mapLength_;
+
+  // Include the entire start page: round down to page boundary.
+  const auto offMisalign = offset % options_.pageSize;
+  offset -= offMisalign;
+  length += offMisalign;
+
+  // Round the last page down to page boundary.
+  if (offset + length != size_t(mapLength_)) {
+    length -= length % options_.pageSize;
   }
+
+  if (length == 0) {
+    return;
+  }
+
+  char* mapStart = static_cast<char*>(mapStart_) + offset;
+  PLOG_IF(WARNING, ::madvise(mapStart, length, advice)) << "madvise";
 }
 
 MemoryMapping& MemoryMapping::operator=(MemoryMapping other) {
@@ -298,7 +323,7 @@ MemoryMapping& MemoryMapping::operator=(MemoryMapping other) {
   return *this;
 }
 
-void MemoryMapping::swap(MemoryMapping& other) {
+void MemoryMapping::swap(MemoryMapping& other) noexcept {
   using std::swap;
   swap(this->file_, other.file_);
   swap(this->mapStart_, other.mapStart_);
@@ -308,7 +333,7 @@ void MemoryMapping::swap(MemoryMapping& other) {
   swap(this->data_, other.data_);
 }
 
-void swap(MemoryMapping& a, MemoryMapping& b) { a.swap(b); }
+void swap(MemoryMapping& a, MemoryMapping& b) noexcept { a.swap(b); }
 
 void alignedForwardMemcpy(void* dst, const void* src, size_t size) {
   assert(reinterpret_cast<uintptr_t>(src) % alignof(unsigned long) == 0);