commit a2e83ab34845759f0999d0ec88f4cdf558c0a9f5
author Ryan Prichard <rprichard@google.com> Fri Aug 16 17:25:43 2019 -0700
committer Ryan Prichard <rprichard@google.com> Thu Aug 22 12:43:17 2019 -0700
tree 94c0adb62490e467936aae54b501c0fb577a122e
parent 3952113d90dd91adc67ce60899d4997bb5f63d0d

Add additional dl_phdr_info fields

Previously, Bionic's dl_phdr_info only included the first four
dl_iterate_phdr fields. Several other libc's have these additional fields:

    unsigned long long dlpi_adds -- incremented when a library is loaded
    unsigned long long dlpi_subs -- incremented when a library is unloaded
    size_t dlpi_tls_modid -- TLS module ID
    void* dlpi_tls_data -- pointer to current thread's TLS block or NULL

These extra fields are also exposed by glibc, musl, and FreeBSD. The
unwinder in libgcc.a, linked into shipping Android DSOs, has a
PC->eh_frame cache that activates if dl_phdr_info has the dlpi_adds and
dlpi_subs fields (indicated at run-time by a sufficiently-large size
argument to the callback).

Bug: https://github.com/android-ndk/ndk/issues/1062
Test: bionic unit tests
Change-Id: I6f0bab548cf8c828af2ddab9eb01c5c6d70cd81f

libc/bionic/dl_iterate_phdr_static.cpp

diff --git a/libc/bionic/dl_iterate_phdr_static.cpp b/libc/bionic/dl_iterate_phdr_static.cpp
index bbce1fc..7b44810 100644
--- a/libc/bionic/dl_iterate_phdr_static.cpp
+++ b/libc/bionic/dl_iterate_phdr_static.cpp
@@ -32,6 +32,10 @@
 #include <sys/types.h>
 #include <link.h>
 
+#include "private/bionic_elf_tls.h"
+#include "private/bionic_globals.h"
+#include "pthread_internal.h"
+
 /* ld provides this to us in the default link script */
 extern "C" void* __executable_start;
 
@@ -52,6 +56,21 @@
   exe_info.dlpi_name = NULL;
   exe_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(ehdr) + ehdr->e_phoff);
   exe_info.dlpi_phnum = ehdr->e_phnum;
+  exe_info.dlpi_adds = 0;
+  exe_info.dlpi_subs = 0;
+
+  const TlsModules& tls_modules = __libc_shared_globals()->tls_modules;
+  if (tls_modules.module_count == 0) {
+    exe_info.dlpi_tls_modid = 0;
+    exe_info.dlpi_tls_data = nullptr;
+  } else {
+    const size_t kExeModuleId = 1;
+    const StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
+    const TlsModule& tls_module = tls_modules.module_table[__tls_module_id_to_idx(kExeModuleId)];
+    char* static_tls = reinterpret_cast<char*>(__get_bionic_tcb()) - layout.offset_bionic_tcb();
+    exe_info.dlpi_tls_modid = kExeModuleId;
+    exe_info.dlpi_tls_data = static_tls + tls_module.static_offset;
+  }
 
   // Try the executable first.
   int rc = cb(&exe_info, sizeof(exe_info), data);
@@ -71,6 +90,10 @@
   vdso_info.dlpi_name = NULL;
   vdso_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
   vdso_info.dlpi_phnum = ehdr_vdso->e_phnum;
+  vdso_info.dlpi_adds = 0;
+  vdso_info.dlpi_subs = 0;
+  vdso_info.dlpi_tls_modid = 0;
+  vdso_info.dlpi_tls_data = nullptr;
   for (size_t i = 0; i < vdso_info.dlpi_phnum; ++i) {
     if (vdso_info.dlpi_phdr[i].p_type == PT_LOAD) {
       vdso_info.dlpi_addr = (ElfW(Addr)) ehdr_vdso - vdso_info.dlpi_phdr[i].p_vaddr;