commit 126af757c6d6a6447c19236df8d98ba07f21996f
author Dmitriy Ivanov <dimitry@google.com> Wed Oct 07 16:34:20 2015 -0700
committer Dmitriy Ivanov <dimitry@google.com> Tue Oct 27 11:27:34 2015 -0700
tree b303f921749f2bb077096218b22ab20bf789d4be
parent 6a4ddeb56ef2144e98437ae82f84b09ea785e411

Implement load at fixed address feature

Bug: http://b/24683631
Change-Id: I3a39ab526c8f9e213339b60e135e5459d0f41381

linker/linker.cpp

diff --git a/linker/linker.cpp b/linker/linker.cpp
index 926fc9b..9f0b559 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -1995,12 +1995,20 @@
       DL_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
       return nullptr;
     }
+
     if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
         (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
       DL_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET without "
           "ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
       return nullptr;
     }
+
+    if ((extinfo->flags & ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS) != 0 &&
+        (extinfo->flags & (ANDROID_DLEXT_RESERVED_ADDRESS | ANDROID_DLEXT_RESERVED_ADDRESS_HINT)) != 0) {
+      DL_ERR("invalid extended flag combination: ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS is not "
+             "compatible with ANDROID_DLEXT_RESERVED_ADDRESS/ANDROID_DLEXT_RESERVED_ADDRESS_HINT");
+      return nullptr;
+    }
   }
 
   ProtectedDataGuard guard;

linker/linker_phdr.cpp

diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index a26187a..347983e 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -386,8 +386,9 @@
   void* start;
   size_t reserved_size = 0;
   bool reserved_hint = true;
+  bool strict_hint = false;
   // Assume position independent executable by default.
-  uint8_t* mmap_hint = nullptr;
+  void* mmap_hint = nullptr;
 
   if (extinfo != nullptr) {
     if (extinfo->flags & ANDROID_DLEXT_RESERVED_ADDRESS) {
@@ -397,8 +398,11 @@
       reserved_size = extinfo->reserved_size;
     }
 
-    if ((extinfo->flags & ANDROID_DLEXT_FORCE_FIXED_VADDR) != 0) {
+    if (addr != nullptr && (extinfo->flags & ANDROID_DLEXT_FORCE_FIXED_VADDR) != 0) {
       mmap_hint = addr;
+    } else if ((extinfo->flags & ANDROID_DLEXT_LOAD_AT_FIXED_ADDRESS) != 0) {
+      mmap_hint = extinfo->reserved_addr;
+      strict_hint = true;
     }
   }
 
@@ -414,6 +418,12 @@
       DL_ERR("couldn't reserve %zd bytes of address space for \"%s\"", load_size_, name_.c_str());
       return false;
     }
+    if (strict_hint && (start != mmap_hint)) {
+      munmap(start, load_size_);
+      DL_ERR("couldn't reserve %zd bytes of address space at %p for \"%s\"",
+             load_size_, mmap_hint, name_.c_str());
+      return false;
+    }
   } else {
     start = extinfo->reserved_addr;
   }