Merge "Revert "Add randomized padding around shared library mappings.""
diff --git a/linker/linker.cpp b/linker/linker.cpp
index e5450c7..10608f4 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -301,14 +301,13 @@
return;
}
- void* start = reinterpret_cast<void*>(si->has_min_version(6) ? si->get_map_start() : si->base);
- size_t size = si->has_min_version(6) ? si->get_map_size() : si->size;
- if (start != nullptr && size != 0) {
+ if (si->base != 0 && si->size != 0) {
if (!si->is_mapped_by_caller()) {
- munmap(start, size);
+ munmap(reinterpret_cast<void*>(si->base), si->size);
} else {
// remap the region as PROT_NONE, MAP_ANONYMOUS | MAP_NORESERVE
- mmap(start, size, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+ mmap(reinterpret_cast<void*>(si->base), si->size, PROT_NONE,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
}
}
@@ -600,8 +599,6 @@
si_->load_bias = elf_reader.load_bias();
si_->phnum = elf_reader.phdr_count();
si_->phdr = elf_reader.loaded_phdr();
- si_->set_map_start(elf_reader.map_start());
- si_->set_map_size(elf_reader.map_size());
return true;
}
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 74d7a31..9b7a461 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -520,8 +520,7 @@
// Reserve a virtual address range such that if it's limits were extended to the next 2**align
// boundary, it would not overlap with any existing mappings.
-static void* ReserveWithAlignmentPadding(size_t size, size_t align, void** map_start,
- size_t* map_size) {
+static void* ReserveAligned(size_t size, size_t align) {
int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS;
if (align == PAGE_SIZE) {
void* mmap_ptr = mmap(nullptr, size, PROT_NONE, mmap_flags, -1, 0);
@@ -533,12 +532,7 @@
// Allocate enough space so that the end of the desired region aligned up is still inside the
// mapping.
-#if defined(__LP64__)
- constexpr size_t kLibraryPadding = 1ul << 24;
-#else
- constexpr size_t kLibraryPadding = 0;
-#endif
- size_t mmap_size = align_up(size + kLibraryPadding, align) + align - PAGE_SIZE;
+ size_t mmap_size = align_up(size, align) + align - PAGE_SIZE;
uint8_t* mmap_ptr =
reinterpret_cast<uint8_t*>(mmap(nullptr, mmap_size, PROT_NONE, mmap_flags, -1, 0));
if (mmap_ptr == MAP_FAILED) {
@@ -552,18 +546,8 @@
// created. Don't randomize then.
size_t n = is_first_stage_init() ? 0 : arc4random_uniform((last - first) / PAGE_SIZE + 1);
uint8_t* start = first + n * PAGE_SIZE;
- // Unmap the extra space around the allocation.
- // Keep it mapped PROT_NONE on 64-bit targets where address space is plentiful to make it harder
- // to defeat ASLR by probing for readable memory mappings.
-#if defined(__LP64__)
- *map_start = mmap_ptr;
- *map_size = mmap_size;
-#else
munmap(mmap_ptr, start - mmap_ptr);
munmap(start + size, mmap_ptr + mmap_size - (start + size));
- *map_start = start;
- *map_size = size;
-#endif
return start;
}
@@ -587,15 +571,13 @@
load_size_ - address_space->reserved_size, load_size_, name_.c_str());
return false;
}
- start = ReserveWithAlignmentPadding(load_size_, kLibraryAlignment, &map_start_, &map_size_);
+ start = ReserveAligned(load_size_, kLibraryAlignment);
if (start == nullptr) {
DL_ERR("couldn't reserve %zd bytes of address space for \"%s\"", load_size_, name_.c_str());
return false;
}
} else {
start = address_space->start_addr;
- map_start_ = start;
- map_size_ = load_size_;
mapped_by_caller_ = true;
// Update the reserved address space to subtract the space used by this library.
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index 18881ca..5d1cfc2 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -49,8 +49,6 @@
size_t phdr_count() const { return phdr_num_; }
ElfW(Addr) load_start() const { return reinterpret_cast<ElfW(Addr)>(load_start_); }
size_t load_size() const { return load_size_; }
- ElfW(Addr) map_start() const { return reinterpret_cast<ElfW(Addr)>(map_start_); }
- size_t map_size() const { return map_size_; }
ElfW(Addr) load_bias() const { return load_bias_; }
const ElfW(Phdr)* loaded_phdr() const { return loaded_phdr_; }
const ElfW(Dyn)* dynamic() const { return dynamic_; }
@@ -98,10 +96,6 @@
void* load_start_;
// Size in bytes of reserved address space.
size_t load_size_;
- // First page of reserved address space including randomized padding.
- void* map_start_;
- // Size in bytes of reserved address space including randomized padding.
- size_t map_size_;
// Load bias.
ElfW(Addr) load_bias_;
diff --git a/linker/linker_soinfo.cpp b/linker/linker_soinfo.cpp
index 088c17d..4f67003 100644
--- a/linker/linker_soinfo.cpp
+++ b/linker/linker_soinfo.cpp
@@ -900,24 +900,6 @@
g_soinfo_handles_map[handle_] = this;
}
-void soinfo::set_map_start(ElfW(Addr) map_start) {
- CHECK(has_min_version(6));
- map_start_ = map_start;
-}
-ElfW(Addr) soinfo::get_map_start() const {
- CHECK(has_min_version(6));
- return map_start_;
-}
-
-void soinfo::set_map_size(size_t map_size) {
- CHECK(has_min_version(6));
- map_size_ = map_size;
-}
-size_t soinfo::get_map_size() const {
- CHECK(has_min_version(6));
- return map_size_;
-}
-
// TODO(dimitry): Move SymbolName methods to a separate file.
uint32_t calculate_elf_hash(const char* name) {
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index 0ecf8d8..e1a3c30 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -66,7 +66,7 @@
#define FLAG_PRELINKED 0x00000400 // prelink_image has successfully processed this soinfo
#define FLAG_NEW_SOINFO 0x40000000 // new soinfo format
-#define SOINFO_VERSION 6
+#define SOINFO_VERSION 5
ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr);
@@ -345,12 +345,6 @@
SymbolLookupLib get_lookup_lib();
- void set_map_start(ElfW(Addr) map_start);
- ElfW(Addr) get_map_start() const;
-
- void set_map_size(size_t map_size);
- size_t get_map_size() const;
-
private:
bool is_image_linked() const;
void set_image_linked();
@@ -429,10 +423,6 @@
// version >= 5
std::unique_ptr<soinfo_tls> tls_;
std::vector<TlsDynamicResolverArg> tlsdesc_args_;
-
- // version >= 6
- ElfW(Addr) map_start_;
- size_t map_size_;
};
// This function is used by dlvsym() to calculate hash of sym_ver
