[scudo] Implement and enable MemMapLinux

[Chia-hungDuan]

Summary

Most of the implementations are copied from linux.cpp and we will be
keeping those memory functions in linux.cpp for a while until we are
able to switch to use MemMap completely.

The remaining part is SizeClassAllocator32 which hasn't been switched to
use MemMap interface

[Chia-hungDuan]

Slightly improve the semantic of MemMapLinux::remap()

[cferris]

compiler-rt/lib/scudo/standalone/mem_map_linux.cpp

39–40

Is this still necessary? I'm not sure if you need to make this compile on old versions of Android, but PR_SET_VMA and PR_SET_VMA_ANON_NAME are available from the bionic kernel headers.

If you need to make this work on older versions of Android, maybe this should be changed to see if PR_SET_VMA is defined.

141

What happens if reserving fails? Should this function return a bool so that caller can fail gracefully?

[Chia-hungDuan]

Address review comment

[Chia-hungDuan]

Update commit message

[cferris]

A few questions.

compiler-rt/lib/scudo/standalone/mem_map_linux.cpp

96

This is a bit confusing. Why is the MapBase being set to Addr + Size? During the unmap, it doesn't seem like this shoudl happen.

97

Another slightly confusing part, it seems like unmapping would increase the total capacity, not decrease it.

[Chia-hungDuan]

Add more comments

compiler-rt/lib/scudo/standalone/mem_map_linux.cpp

39–40

This is copied from the old file linux.cpp, I added a TODO to mark it and we can discuss the necessity later

96

The unamp() supports partial unmapping but the result pages still have to be contiguous. So we check if the unmap() is either aligned to the begin addr or end addr in MemMapBase::unamp().

So far, this is not used so it's more like a contract for future. Like blocks merging in secondary.

97

Added few comments here. Let me know if it explains more.

141

Done. The API has been changed to return boolean.

[cferris]

LGTM the new comments answered my questions.

compiler-rt/lib/scudo/standalone/CMakeLists.txt

set(SCUDO_HEADERS
   internal_defs.h
   linux.h
   list.h
   local_cache.h
   memtag.h
   mem_map.h
   mem_map_base.h
   mem_map_fuchsia.h
+  mem_map_linux.h
   mutex.h
   options.h
   platform.h
   primary32.h
   primary64.h
   quarantine.h
   release.h
   report.h
set(SCUDO_SOURCES
   common.cpp
   crc32_hw.cpp
   flags_parser.cpp
   flags.cpp
   fuchsia.cpp
   linux.cpp
   mem_map.cpp
   mem_map_fuchsia.cpp
+  mem_map_linux.cpp
   release.cpp
   report.cpp
   rss_limit_checker.cpp
   string_utils.cpp
   timing.cpp
   )
 
 # Temporary hack until LLVM libc supports inttypes.h print format macros

compiler-rt/lib/scudo/standalone/linux.cpp

 #endif
 
 namespace scudo {
 
 uptr getPageSize() { return static_cast<uptr>(sysconf(_SC_PAGESIZE)); }
 
 void NORETURN die() { abort(); }
 
+// TODO: Will be deprecated. Use the interfaces in MemMapLinux instead.
 void *map(void *Addr, uptr Size, UNUSED const char *Name, uptr Flags,
           UNUSED MapPlatformData *Data) {
   int MmapFlags = MAP_PRIVATE | MAP_ANONYMOUS;
   int MmapProt;
   if (Flags & MAP_NOACCESS) {
     MmapFlags |= MAP_NORESERVE;
     MmapProt = PROT_NONE;
   } else {
#endif
   }
 #if SCUDO_ANDROID
   if (Name)
     prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, P, Size, Name);
 #endif
   return P;
 }
 
+// TODO: Will be deprecated. Use the interfaces in MemMapLinux instead.
 void unmap(void *Addr, uptr Size, UNUSED uptr Flags,
            UNUSED MapPlatformData *Data) {
   if (munmap(Addr, Size) != 0)
     dieOnMapUnmapError();
 }
 
+// TODO: Will be deprecated. Use the interfaces in MemMapLinux instead.
 void setMemoryPermission(uptr Addr, uptr Size, uptr Flags,
                          UNUSED MapPlatformData *Data) {
   int Prot = (Flags & MAP_NOACCESS) ? PROT_NONE : (PROT_READ | PROT_WRITE);
   if (mprotect(reinterpret_cast<void *>(Addr), Size, Prot) != 0)
     dieOnMapUnmapError();
 }
 
+// TODO: Will be deprecated. Use the interfaces in MemMapLinux instead.
 void releasePagesToOS(uptr BaseAddress, uptr Offset, uptr Size,
                       UNUSED MapPlatformData *Data) {
   void *Addr = reinterpret_cast<void *>(BaseAddress + Offset);
 
   while (madvise(Addr, Size, MADV_DONTNEED) == -1 && errno == EAGAIN) {
   }
 }
 

compiler-rt/lib/scudo/standalone/mem_map.h

 // TODO: This is only used for `MapPlatformData`. Remove these includes when we
 // have all three platform specific `MemMap` and `ReservedMemory`
 // implementations.
 #include "fuchsia.h"
 #include "linux.h"
 #include "trusty.h"
 
 #include "mem_map_fuchsia.h"
+#include "mem_map_linux.h"
 
 namespace scudo {
 
 // This will be deprecated when every allocator has been supported by each
 // platform's `MemMap` implementation.
 class MemMapDefault final : public MemMapBase<MemMapDefault> {
 public:
   constexpr MemMapDefault() = default;

 
 private:
   uptr Base = 0;
   uptr Capacity = 0;
   MapPlatformData Data = {};
 };
 
 #if SCUDO_LINUX
-using ReservedMemoryT = ReservedMemoryDefault;
+using ReservedMemoryT = ReservedMemoryLinux;
 using MemMapT = ReservedMemoryT::MemMapT;
 #elif SCUDO_FUCHSIA
 using ReservedMemoryT = ReservedMemoryFuchsia;
 using MemMapT = ReservedMemoryT::MemMapT;
 #elif SCUDO_TRUSTY
 using ReservedMemoryT = ReservedMemoryDefault;
 using MemMapT = ReservedMemoryT::MemMapT;
 #else
 #error                                                                         \
     "Unsupported platform, please implement the ReservedMemory for your platform!"
 #endif
 
 } // namespace scudo
 
 #endif // SCUDO_MEM_MAP_H_

compiler-rt/lib/scudo/standalone/mem_map_linux.h

+//===-- mem_map_linux.h -----------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SCUDO_MEM_MAP_LINUX_H_
+#define SCUDO_MEM_MAP_LINUX_H_
+
+#include "platform.h"
+
+#if SCUDO_LINUX
+
+#include "common.h"
+#include "mem_map_base.h"
+
+namespace scudo {
+
+class MemMapLinux final : public MemMapBase<MemMapLinux> {
+public:
+  constexpr MemMapLinux() = default;
+  MemMapLinux(uptr Base, uptr Capacity)
+      : MapBase(Base), MapCapacity(Capacity) {}
+
+  // Impls for base functions.
+  bool mapImpl(uptr Addr, uptr Size, const char *Name, uptr Flags = 0);
+  void unmapImpl(uptr Addr, uptr Size);
+  bool remapImpl(uptr Addr, uptr Size, const char *Name, uptr Flags = 0);
+  void setMemoryPermissionImpl(uptr Addr, uptr Size, uptr Flags);
+  void releasePagesToOSImpl(uptr From, uptr Size) {
+    return releaseAndZeroPagesToOSImpl(From, Size);
+  }
+  void releaseAndZeroPagesToOSImpl(uptr From, uptr Size);
+  uptr getBaseImpl() { return MapBase; }
+  uptr getCapacityImpl() { return MapCapacity; }
+
+private:
+  uptr MapBase = 0;
+  uptr MapCapacity = 0;
+};
+
+// This will be deprecated when every allocator has been supported by each
+// platform's `MemMap` implementation.
+class ReservedMemoryLinux final
+    : public ReservedMemory<ReservedMemoryLinux, MemMapLinux> {
+public:
+  // The following two are the Impls for function in `MemMapBase`.
+  uptr getBaseImpl() { return MapBase; }
+  uptr getCapacityImpl() { return MapCapacity; }
+
+  // These threes are specific to `ReservedMemory`.
+  bool createImpl(uptr Addr, uptr Size, const char *Name, uptr Flags);
+  void releaseImpl();
+  MemMapT dispatchImpl(uptr Addr, uptr Size);
+
+private:
+  uptr MapBase = 0;
+  uptr MapCapacity = 0;
+};
+
+} // namespace scudo
+
+#endif // SCUDO_LINUX
+
+#endif // SCUDO_MEM_MAP_LINUX_H_

compiler-rt/lib/scudo/standalone/mem_map_linux.cpp

+//===-- mem_map_linux.cpp ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "platform.h"
+
+#if SCUDO_LINUX
+
+#include "mem_map_linux.h"
+
+#include "common.h"
+#include "internal_defs.h"
+#include "linux.h"
+#include "mutex.h"
+#include "string_utils.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/futex.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#if SCUDO_ANDROID
+// TODO(chiahungduan): Review if we still need the followings macros.
+#include <sys/prctl.h>
+// Definitions of prctl arguments to set a vma name in Android kernels.
+#define ANDROID_PR_SET_VMA 0x53564d41
+#define ANDROID_PR_SET_VMA_ANON_NAME 0
+#endif
+
+namespace scudo {
+
+static void *mmapWrapper(uptr Addr, uptr Size, const char *Name, uptr Flags) {
+  int MmapFlags = MAP_PRIVATE | MAP_ANONYMOUS;
+  int MmapProt;
+  if (Flags & MAP_NOACCESS) {
+    MmapFlags |= MAP_NORESERVE;
+    MmapProt = PROT_NONE;
+  } else {
+    MmapProt = PROT_READ | PROT_WRITE;
+  }
+#if defined(__aarch64__)
+#ifndef PROT_MTE
+#define PROT_MTE 0x20
+#endif
+  if (Flags & MAP_MEMTAG)
+    MmapProt |= PROT_MTE;
+#endif
+  if (Addr)
+    MmapFlags |= MAP_FIXED;
+  void *P =
+      mmap(reinterpret_cast<void *>(Addr), Size, MmapProt, MmapFlags, -1, 0);
+  if (P == MAP_FAILED) {
+    if (!(Flags & MAP_ALLOWNOMEM) || errno != ENOMEM)
+      dieOnMapUnmapError(errno == ENOMEM ? Size : 0);
+    return nullptr;
+  }
+#if SCUDO_ANDROID
+  if (Name)
+    prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, P, Size, Name);
+#else
+  (void)Name;
+#endif
+
+  return P;
+}
+
+bool MemMapLinux::mapImpl(uptr Addr, uptr Size, const char *Name, uptr Flags) {
+  void *P = mmapWrapper(Addr, Size, Name, Flags);
+  if (P == nullptr)
+    return false;
+
+  MapBase = reinterpret_cast<uptr>(P);
+  MapCapacity = Size;
+  return true;
+}
+
+void MemMapLinux::unmapImpl(uptr Addr, uptr Size) {
+  // If we unmap all the pages, also mark `MapBase` to 0 to indicate invalid
+  // status.
+  if (Size == MapCapacity) {
+    MapBase = MapCapacity = 0;
+  } else {
+    // This is partial unmap and is unmapping the pages from the beginning,
+    // shift `MapBase` to the new base.
+    if (MapBase == Addr)
+      MapBase = Addr + Size;
+    MapCapacity -= Size;
+  }
+
+  if (munmap(reinterpret_cast<void *>(Addr), Size) != 0)
+    dieOnMapUnmapError();
+}
+
+bool MemMapLinux::remapImpl(uptr Addr, uptr Size, const char *Name,
+                            uptr Flags) {
+  void *P = mmapWrapper(Addr, Size, Name, Flags);
+  if (reinterpret_cast<uptr>(P) != Addr)
+    dieOnMapUnmapError();
+  return true;
+}
+
+void MemMapLinux::setMemoryPermissionImpl(uptr Addr, uptr Size, uptr Flags) {
+  int Prot = (Flags & MAP_NOACCESS) ? PROT_NONE : (PROT_READ | PROT_WRITE);
+  if (mprotect(reinterpret_cast<void *>(Addr), Size, Prot) != 0)
+    dieOnMapUnmapError();
+}
+
+void MemMapLinux::releaseAndZeroPagesToOSImpl(uptr From, uptr Size) {
+  void *Addr = reinterpret_cast<void *>(From);
+
+  while (madvise(Addr, Size, MADV_DONTNEED) == -1 && errno == EAGAIN) {
+  }
+}
+
+bool ReservedMemoryLinux::createImpl(uptr Addr, uptr Size, const char *Name,
+                                     uptr Flags) {
+  ReservedMemoryLinux::MemMapT MemMap;
+  if (!MemMap.map(Addr, Size, Name, Flags | MAP_NOACCESS))
+    return false;
+
+  MapBase = MemMap.getBase();
+  MapCapacity = MemMap.getCapacity();
+
+  return true;
+}
+
+void ReservedMemoryLinux::releaseImpl() {
+  if (munmap(reinterpret_cast<void *>(getBase()), getCapacity()) != 0)
+    dieOnMapUnmapError();
+}
+
+ReservedMemoryLinux::MemMapT ReservedMemoryLinux::dispatchImpl(uptr Addr,
+                                                               uptr Size) {
+  return ReservedMemoryLinux::MemMapT(Addr, Size);
+}
+
+} // namespace scudo
+
+#endif // SCUDO_LINUX