From b066d43b1d9184899aff32b1f243d092611ad9c6 Mon Sep 17 00:00:00 2001
From: Vladimir Marko <vmarko@google.com>
Date: Wed, 3 Jan 2018 13:14:37 +0000
Subject: Load ArtMethod* from .data.bimg.rel.ro entries.

Introduce a new .data.bimg.rel.ro section in oat files where
we store offsets of boot image objects from the beginning of
the boot image. At runtime we relocate these entries using
the actual boot image address to turn offsets to pointers.

Use the .data.bimg.rel.ro to prepare the boot image methods
used by HInvokeStaticOrDirect for PIC AOT app compilation.
Loading the ArtMethod* from .data.bimg.rel.ro instead of the
.bss avoids the initial call to the resolution trampoline.

Test: Additional test in 522-checker-sharpening
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing --pictest --npictest
Test: Pixel 2 XL boots.
Test: testrunner.py --target --optimizing --pictest --npictest
Bug: 71526895
Change-Id: Ie5f5b1f622704877b36730377146e59092e46c0c
---
 compiler/linker/elf_builder.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'compiler/linker/elf_builder.h')

diff --git a/compiler/linker/elf_builder.h b/compiler/linker/elf_builder.h
index a5f60992ca..3da7a43762 100644
--- a/compiler/linker/elf_builder.h
+++ b/compiler/linker/elf_builder.h
@@ -529,6 +529,8 @@ class ElfBuilder FINAL {
         stream_(output),
         rodata_(this, ".rodata", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0),
         text_(this, ".text", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR, nullptr, 0, kPageSize, 0),
+        data_bimg_rel_ro_(
+            this, ".data.bimg.rel.ro", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0),
         bss_(this, ".bss", SHT_NOBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0),
         dex_(this, ".dex", SHT_NOBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0),
         dynstr_(this, ".dynstr", SHF_ALLOC, kPageSize),
@@ -552,6 +554,7 @@ class ElfBuilder FINAL {
         loaded_size_(0u),
         virtual_address_(0) {
     text_.phdr_flags_ = PF_R | PF_X;
+    data_bimg_rel_ro_.phdr_flags_ = PF_R | PF_W;  // Shall be made read-only at run time.
     bss_.phdr_flags_ = PF_R | PF_W;
     dex_.phdr_flags_ = PF_R;
     dynamic_.phdr_flags_ = PF_R | PF_W;
@@ -566,6 +569,7 @@ class ElfBuilder FINAL {
   BuildIdSection* GetBuildId() { return &build_id_; }
   Section* GetRoData() { return &rodata_; }
   Section* GetText() { return &text_; }
+  Section* GetDataBimgRelRo() { return &data_bimg_rel_ro_; }
   Section* GetBss() { return &bss_; }
   Section* GetDex() { return &dex_; }
   StringSection* GetStrTab() { return &strtab_; }
@@ -694,6 +698,7 @@ class ElfBuilder FINAL {
   void PrepareDynamicSection(const std::string& elf_file_path,
                              Elf_Word rodata_size,
                              Elf_Word text_size,
+                             Elf_Word data_bimg_rel_ro_size,
                              Elf_Word bss_size,
                              Elf_Word bss_methods_offset,
                              Elf_Word bss_roots_offset,
@@ -707,6 +712,9 @@ class ElfBuilder FINAL {
     // Allocate all pre-dynamic sections.
     rodata_.AllocateVirtualMemory(rodata_size);
     text_.AllocateVirtualMemory(text_size);
+    if (data_bimg_rel_ro_size != 0) {
+      data_bimg_rel_ro_.AllocateVirtualMemory(data_bimg_rel_ro_size);
+    }
     if (bss_size != 0) {
       bss_.AllocateVirtualMemory(bss_size);
     }
@@ -735,6 +743,24 @@ class ElfBuilder FINAL {
       Elf_Word oatlastword_address = rodata_.GetAddress() + rodata_size - 4;
       dynsym_.Add(oatlastword, &rodata_, oatlastword_address, 4, STB_GLOBAL, STT_OBJECT);
     }
+    if (data_bimg_rel_ro_size != 0u) {
+      Elf_Word oatdatabimgrelro = dynstr_.Add("oatdatabimgrelro");
+      dynsym_.Add(oatdatabimgrelro,
+                  &data_bimg_rel_ro_,
+                  data_bimg_rel_ro_.GetAddress(),
+                  data_bimg_rel_ro_size,
+                  STB_GLOBAL,
+                  STT_OBJECT);
+      Elf_Word oatdatabimgrelrolastword = dynstr_.Add("oatdatabimgrelrolastword");
+      Elf_Word oatdatabimgrelrolastword_address =
+          data_bimg_rel_ro_.GetAddress() + data_bimg_rel_ro_size - 4;
+      dynsym_.Add(oatdatabimgrelrolastword,
+                  &data_bimg_rel_ro_,
+                  oatdatabimgrelrolastword_address,
+                  4,
+                  STB_GLOBAL,
+                  STT_OBJECT);
+    }
     DCHECK_LE(bss_roots_offset, bss_size);
     if (bss_size != 0u) {
       Elf_Word oatbss = dynstr_.Add("oatbss");
@@ -1010,6 +1036,7 @@ class ElfBuilder FINAL {
 
   Section rodata_;
   Section text_;
+  Section data_bimg_rel_ro_;
   Section bss_;
   Section dex_;
   CachedStringSection dynstr_;
-- 
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