Bug 1898382 - Remove Android < 5.0 specific code from the linker. r=gsvelto

Also remove workarounds for older NDKs.

Differential Revision: https://phabricator.services.mozilla.com/D211299

mozglue/linker/ElfLoader.cpp

@@ -7,6 +7,7 @@
 #include <cstdlib>
 #include <cstdio>
 #include <dlfcn.h>
+#include <link.h>
 #include <optional>
 #include <unistd.h>
 #include <errno.h>
@@ -55,12 +56,6 @@ extern "C" MOZ_EXPORT const void* __gnu_Unwind_Find_exidx(void* pc, int* pcount)
     __attribute__((weak));
 #endif
 
-/* Ideally we'd #include <link.h>, but that's a world of pain
- * Moreover, not all versions of android support it, so we need a weak
- * reference. */
-extern "C" MOZ_EXPORT int dl_iterate_phdr(dl_phdr_cb callback, void* data)
-    __attribute__((weak));
-
 /* Pointer to the PT_DYNAMIC section of the executable or library
  * containing this code. */
 extern "C" Elf::Dyn _DYNAMIC[];
@@ -246,7 +241,6 @@ int __wrap_dl_iterate_phdr(dl_phdr_cb callback, void* data) {
   DlIteratePhdrHelper helper;
   AutoLock lock(&ElfLoader::Singleton.handlesMutex);
 
-  if (dl_iterate_phdr) {
   for (ElfLoader::LibHandleList::reverse_iterator it =
            ElfLoader::Singleton.handles.rbegin();
        it < ElfLoader::Singleton.handles.rend(); ++it) {
@@ -254,25 +248,11 @@ int __wrap_dl_iterate_phdr(dl_phdr_cb callback, void* data) {
     if (!elf) {
       continue;
     }
-      int ret = helper.fill_and_call(callback, (*it)->GetBase(),
-                                     (*it)->GetPath(), data);
+    int ret = helper.fill_and_call(callback, (*it)->GetBase(), (*it)->GetPath(),
+                                   data);
     if (ret) return ret;
   }
   return dl_iterate_phdr(callback, data);
-  }
-
-  /* For versions of Android that don't support dl_iterate_phdr (< 5.0),
-   * we go through the debugger helper data, which is known to be racy, but
-   * there's not much we can do about this :( . */
-  if (!ElfLoader::Singleton.dbg) return -1;
-
-  for (ElfLoader::DebuggerHelper::iterator it =
-           ElfLoader::Singleton.dbg.begin();
-       it < ElfLoader::Singleton.dbg.end(); ++it) {
-    int ret = helper.fill_and_call(callback, it->l_addr, it->l_name, data);
-    if (ret) return ret;
-  }
-  return 0;
 }
 
 #ifdef __ARM_EABI__
@@ -304,11 +284,6 @@ const char* LeafName(const char* path) {
  */
 template <class Lambda>
 static bool RunWithSystemLinkerLock(Lambda&& aLambda) {
-  if (!dl_iterate_phdr) {
-    // No dl_iterate_phdr support.
-    return false;
-  }
-
 #if defined(ANDROID)
   if (GetAndroidSDKVersion() < 23) {
     // dl_iterate_phdr is _not_ protected by a lock on Android < 23.
@@ -530,19 +505,6 @@ void ElfLoader::Init() {
   if (dladdr(_DYNAMIC, &info) != 0) {
     self_elf = LoadedElf::Create(info.dli_fname, info.dli_fbase);
   }
-#if defined(ANDROID)
-  // On Android < 5.0, resolving weak symbols via dlsym doesn't work.
-  // The weak symbols Gecko uses are in either libc or libm, so we
-  // wrap those such that this linker does symbol resolution for them.
-  if (GetAndroidSDKVersion() < 21) {
-    if (dladdr(FunctionPtr(syscall), &info) != 0) {
-      libc = LoadedElf::Create(info.dli_fname, info.dli_fbase);
-    }
-    if (dladdr(FunctionPtr<int (*)(double)>(isnan), &info) != 0) {
-      libm = LoadedElf::Create(info.dli_fname, info.dli_fbase);
-    }
-  }
-#endif
 }
 
 ElfLoader::~ElfLoader() {
@@ -554,10 +516,6 @@ ElfLoader::~ElfLoader() {
 
   /* Release self_elf and libc */
   self_elf = nullptr;
-#if defined(ANDROID)
-  libc = nullptr;
-  libm = nullptr;
-#endif
 
   AutoLock lock(&handlesMutex);
   /* Build up a list of all library handles with direct (external) references.
@@ -701,8 +659,7 @@ ElfLoader::DebuggerHelper::DebuggerHelper()
 
   /* Finally, scan forward to find the last environment variable pointer and
    * thus the first auxiliary vector. */
-  while (*scan++)
-    ;
+  while (*scan++);
 
   /* Some platforms have more NULLs here, so skip them if we encounter them */
   while (!*scan) scan++;

mozglue/linker/ElfLoader.h

@@ -34,13 +34,6 @@ typedef struct {
 #endif
 int __wrap_dladdr(const void* addr, Dl_info* info);
 
-struct dl_phdr_info {
-  Elf::Addr dlpi_addr;
-  const char* dlpi_name;
-  const Elf::Phdr* dlpi_phdr;
-  Elf::Half dlpi_phnum;
-};
-
 typedef int (*dl_phdr_cb)(struct dl_phdr_info*, size_t, void*);
 int __wrap_dl_iterate_phdr(dl_phdr_cb callback, void* data);
 
@@ -408,17 +401,6 @@ class ElfLoader : public SEGVHandler {
    * is used to resolve wrapped functions. */
   RefPtr<LibHandle> self_elf;
 
-#if defined(ANDROID)
-  /* System loader handle for the libc. This is used to resolve weak symbols
-   * that some libcs contain that the Android linker won't dlsym(). Normally,
-   * we wouldn't treat non-Android differently, but glibc uses versioned
-   * symbols which this linker doesn't support. */
-  RefPtr<LibHandle> libc;
-
-  /* And for libm. */
-  RefPtr<LibHandle> libm;
-#endif
-
   /* Bookkeeping */
   typedef std::vector<LibHandle*> LibHandleList;
   LibHandleList handles;

mozglue/linker/Elfxx.h

@@ -7,21 +7,9 @@
 
 #include "Utils.h"
 
-/**
- * Android system headers have two different elf.h file. The one under linux/
- * is the most complete on older Android API versions without unified headers.
- */
-#if defined(ANDROID) && __ANDROID_API__ < 21 && !defined(__ANDROID_API_L__)
-#  include <linux/elf.h>
-#else
-#  include <elf.h>
-#endif
+#include <elf.h>
 #include <endian.h>
 
-#if defined(__ARM_EABI__) && !defined(PT_ARM_EXIDX)
-#  define PT_ARM_EXIDX 0x70000001
-#endif
-
 /**
  * Generic ELF macros for the target system
  */
@@ -128,58 +116,6 @@
 #  error Unknown ELF machine type
 #endif
 
-/**
- * Android system headers don't have all definitions
- */
-#ifndef STN_UNDEF
-#  define STN_UNDEF 0
-#endif
-#ifndef DT_INIT_ARRAY
-#  define DT_INIT_ARRAY 25
-#endif
-#ifndef DT_FINI_ARRAY
-#  define DT_FINI_ARRAY 26
-#endif
-#ifndef DT_INIT_ARRAYSZ
-#  define DT_INIT_ARRAYSZ 27
-#endif
-#ifndef DT_FINI_ARRAYSZ
-#  define DT_FINI_ARRAYSZ 28
-#endif
-#ifndef DT_RELACOUNT
-#  define DT_RELACOUNT 0x6ffffff9
-#endif
-#ifndef DT_RELCOUNT
-#  define DT_RELCOUNT 0x6ffffffa
-#endif
-#ifndef DT_VERSYM
-#  define DT_VERSYM 0x6ffffff0
-#endif
-#ifndef DT_VERDEF
-#  define DT_VERDEF 0x6ffffffc
-#endif
-#ifndef DT_VERDEFNUM
-#  define DT_VERDEFNUM 0x6ffffffd
-#endif
-#ifndef DT_VERNEED
-#  define DT_VERNEED 0x6ffffffe
-#endif
-#ifndef DT_VERNEEDNUM
-#  define DT_VERNEEDNUM 0x6fffffff
-#endif
-#ifndef DT_FLAGS_1
-#  define DT_FLAGS_1 0x6ffffffb
-#endif
-#ifndef DT_FLAGS
-#  define DT_FLAGS 30
-#endif
-#ifndef DF_SYMBOLIC
-#  define DF_SYMBOLIC 0x00000002
-#endif
-#ifndef DF_TEXTREL
-#  define DF_TEXTREL 0x00000004
-#endif
-
 namespace Elf {
 
 /**
@@ -220,26 +156,29 @@ class Strtab : public UnsizedArray<const char> {
 /**
  * Helper class around Elf relocation.
  */
-struct Rel : public Elf_(Rel) {
-  /**
-   * Returns the addend for the relocation, which is the value stored
-   * at r_offset.
+struct Rel
+    : public Elf_(Rel){/**
+                        * Returns the addend for the relocation, which is the
+                        * value stored at r_offset.
                         */
-  Addr GetAddend(void* base) const {
-    return *(reinterpret_cast<const Addr*>(reinterpret_cast<const char*>(base) +
-                                           r_offset));
-  }
-};
+                       Addr GetAddend(void* base)
+                           const {return *(reinterpret_cast<const Addr*>(
+                               reinterpret_cast<const char*>(base) + r_offset));
+}  // namespace Elf
+}
+;
 
 /**
  * Helper class around Elf relocation with addend.
  */
-struct Rela : public Elf_(Rela) {
-  /**
+struct Rela
+    : public Elf_(Rela){/**
                          * Returns the addend for the relocation.
                          */
-  Addr GetAddend(void* base) const { return r_addend; }
-};
+                        Addr GetAddend(void* base) const {return r_addend;
+}
+}
+;
 
 } /* namespace Elf */