Do not unmap twice a mapping.

Put the mappings in mode 'reuse', as the mremaps following in the
methods will have unmapped them.

Test: m
Bug: 363118250
Bug: 319203762
Change-Id: I1c4eae39df1d0b175a83bb4f0cc9af53b400a931

2 files changed, 26 insertions, 9 deletions

diff --git a/libartbase/base/mem_map.h b/libartbase/base/mem_map.h
index a3af44fadb..4b4a56a23f 100644
--- a/libartbase/base/mem_map.h
+++ b/libartbase/base/mem_map.h
@@ -220,6 +220,28 @@ class MemMap {
                             error_msg);
   }
 
+  static MemMap MapFile(size_t byte_count,
+                        int prot,
+                        int flags,
+                        int fd,
+                        off_t start,
+                        bool low_4gb,
+                        const char* filename,
+                        bool reuse,
+                        std::string* error_msg) {
+    return MapFileAtAddress(nullptr,
+                            byte_count,
+                            prot,
+                            flags,
+                            fd,
+                            start,
+                            /*low_4gb=*/ low_4gb,
+                            filename,
+                            reuse,
+                            /*reservation=*/ nullptr,
+                            error_msg);
+  }
+
   // Map part of a file, taking care of non-page aligned offsets. The "start" offset is absolute,
   // not relative. This version allows requesting a specific address for the base of the mapping.
   //
@@ -425,8 +447,8 @@ class MemMap {
   size_t base_size_ = 0u;       // Length of mapping. May be changed by RemapAtEnd (ie Zygote).
   int prot_ = 0;                // Protection of the map.
 
-  // When reuse_ is true, this is just a view of an existing mapping
-  // and we do not take ownership and are not responsible for
+  // When reuse_ is true, this is a view of a mapping on which
+  // we do not take ownership and are not responsible for
   // unmapping.
   bool reuse_ = false;
 
diff --git a/runtime/jit/jit.cc b/runtime/jit/jit.cc
index 567f07adf0..bdfb911003 100644
--- a/runtime/jit/jit.cc
+++ b/runtime/jit/jit.cc
@@ -568,6 +568,7 @@ void Jit::NotifyZygoteCompilationDone() {
       /* start= */ 0,
       /* low_4gb= */ false,
       "boot-image-methods",
+      /* reuse= */ true,  // The mapping will be reused by the mremaps below.
       &error_str);
 
   if (!child_mapping_methods.IsValid()) {
@@ -640,10 +641,6 @@ void Jit::NotifyZygoteCompilationDone() {
   // Mark that compilation of boot classpath is done, and memory can now be
   // shared. Other processes will pick up this information.
   code_cache_->GetZygoteMap()->SetCompilationState(ZygoteCompilationState::kNotifiedOk);
-
-  // The private mapping created for this process has been mremaped. We can
-  // reset it.
-  child_mapping_methods.Reset();
 }
 
 class JitCompileTask final : public Task {
@@ -975,6 +972,7 @@ void Jit::MapBootImageMethods() {
       /* start= */ 0,
       /* low_4gb= */ false,
       "boot-image-methods",
+      /* reuse= */ true,  // The mapping will be reused by the mremaps below.
       &error_str);
 
   // We don't need the fd anymore.
@@ -1071,9 +1069,6 @@ void Jit::MapBootImageMethods() {
     offset += capacity;
   }
 
-  // The private mapping created for this process has been mremaped. We can
-  // reset it.
-  child_mapping_methods.Reset();
   LOG(INFO) << "Successfully mapped boot image methods";
 }