commit e4d620bc805aa675924a4f50c7179195126d65a6
author Ryan Prichard <rprichard@google.com> Mon Apr 01 17:42:14 2019 -0700
committer Ryan Prichard <rprichard@google.com> Wed Apr 03 18:19:50 2019 -0700
tree 02318e36d725bc2d9be96ba86cd9cc8ae3bef927
parent db6edcca36082a1a7b7e258e5d48f242695d827b

Fix dlsym and dladdr for TLS symbols

 * dlsym: call __tls_get_addr for TLS symbols

 * dladdr: skip TLS symbols

Bug: b/123772574
Test: bionic unit tests
Change-Id: I59a8bc4a7d455e1018b0d577b027b6417c8487cd

linker/linker.cpp

diff --git a/linker/linker.cpp b/linker/linker.cpp
index c60ab6a..044689f 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -2383,9 +2383,26 @@
 
   if (sym != nullptr) {
     uint32_t bind = ELF_ST_BIND(sym->st_info);
+    uint32_t type = ELF_ST_TYPE(sym->st_info);
 
     if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
-      *symbol = reinterpret_cast<void*>(found->resolve_symbol_address(sym));
+      if (type == STT_TLS) {
+        // For a TLS symbol, dlsym returns the address of the current thread's
+        // copy of the symbol. This function may allocate a DTV and/or storage
+        // for the source TLS module. (Allocating a DTV isn't necessary if the
+        // symbol is part of static TLS, but it's simpler to reuse
+        // __tls_get_addr.)
+        soinfo_tls* tls_module = found->get_tls();
+        if (tls_module == nullptr) {
+          DL_ERR("TLS symbol \"%s\" in solib \"%s\" with no TLS segment",
+                 sym_name, found->get_realpath());
+          return false;
+        }
+        const TlsIndex ti { tls_module->module_id, sym->st_value };
+        *symbol = TLS_GET_ADDR(&ti);
+      } else {
+        *symbol = reinterpret_cast<void*>(found->resolve_symbol_address(sym));
+      }
       failure_guard.Disable();
       LD_LOG(kLogDlsym,
              "... dlsym successful: sym_name=\"%s\", sym_ver=\"%s\", found in=\"%s\", address=%p",

linker/linker_soinfo.cpp

diff --git a/linker/linker_soinfo.cpp b/linker/linker_soinfo.cpp
index 89119aa..31ee74c 100644
--- a/linker/linker_soinfo.cpp
+++ b/linker/linker_soinfo.cpp
@@ -297,7 +297,11 @@
 }
 
 static bool symbol_matches_soaddr(const ElfW(Sym)* sym, ElfW(Addr) soaddr) {
+  // Skip TLS symbols. A TLS symbol's value is relative to the start of the TLS segment rather than
+  // to the start of the solib. The solib only reserves space for the initialized part of the TLS
+  // segment. (i.e. .tdata is followed by .tbss, and .tbss overlaps other sections.)
   return sym->st_shndx != SHN_UNDEF &&
+      ELF_ST_TYPE(sym->st_info) != STT_TLS &&
       soaddr >= sym->st_value &&
       soaddr < sym->st_value + sym->st_size;
 }