Added support for reading thread-local storage variables, as defined using the __thread modifier.

To make this work this patch extends LLDB to:

- Explicitly track the link_map address for each module. This is effectively the module handle, not sure why it wasn't already being stored off anywhere. As an extension later, it would be nice if someone were to add support for printing this as part of the modules list.

- Allow reading the per-thread data pointer via ptrace. I have added support for Linux here. I'll be happy to add support for FreeBSD once this is reviewed. OS X does not appear to have __thread variables, so maybe we don't need it there. Windows support should eventually be workable along the same lines.

- Make DWARF expressions track which module they originated from.

- Add support for the DW_OP_GNU_push_tls_address DWARF opcode, as generated by gcc and recent versions of clang. Earlier versions of clang (such as 3.2, which is default on Ubuntu right now) do not generate TLS debug info correctly so can not be supported here.

- Understand the format of the pthread DTV block. This is where it gets tricky. We have three basic options here:

  1) Call "dlinfo" or "__tls_get_addr" on the inferior and ask it directly. However this won't work on core dumps, and generally speaking it's not a good idea for the debugger to call functions itself, as it has the potential to not work depending on the state of the target.

  2) Use libthread_db. This is what GDB does. However this option requires having a version of libthread_db on the host cross-compiled for each potential target. This places a large burden on the user, and would make it very hard to cross-debug from Windows to Linux, for example. Trying to build a library intended exclusively for one OS on a different one is not pleasant. GDB sidesteps the problem and asks the user to figure it out.

  3) Parse the DTV structure ourselves. On initial inspection this seems to be a bad option, as the DTV structure (the format used by the runtime to manage TLS data) is not in fact a kernel data structure, it is implemented entirely in useerland in libc. Therefore the layout of it's fields are version and OS dependent, and are not standardized.

  However, it turns out not to be such a problem. All OSes use basically the same algorithm (a per-module lookup table) as detailed in Ulrich Drepper's TLS ELF ABI document, so we can easily write code to decode it ourselves. The only question therefore is the exact field layouts required. Happily, the implementors of libpthread expose the structure of the DTV via metadata exported as symbols from the .so itself, designed exactly for this kind of thing. So this patch simply reads that metadata in, and re-implements libthread_db's algorithm itself. We thereby get cross-platform TLS lookup without either requiring third-party libraries, while still being independent of the version of libpthread being used.

Test case included.

llvm-svn: 192922

4 files changed, 168 insertions, 11 deletions

diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp
index 556df606248..3c5dcc5222a 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp
@@ -14,6 +14,7 @@
 #include "lldb/Core/Error.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
+#include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/Target.h"
 
@@ -55,6 +56,8 @@ DYLDRendezvous::DYLDRendezvous(Process *process)
       m_added_soentries(),
       m_removed_soentries()
 {
+    m_thread_info.valid = false;
+
     // Cache a copy of the executable path
     if (m_process)
     {
@@ -284,6 +287,8 @@ bool
 DYLDRendezvous::ReadSOEntryFromMemory(lldb::addr_t addr, SOEntry &entry)
 {
     entry.clear();
+
+    entry.link_addr = addr;
     
     if (!(addr = ReadPointer(addr, &entry.base_addr)))
         return false;
@@ -320,6 +325,51 @@ DYLDRendezvous::ReadSOEntryFromMemory(lldb::addr_t addr, SOEntry &entry)
     return true;
 }
 
+
+bool
+DYLDRendezvous::FindMetadata(const char *name, PThreadField field, uint32_t& value)
+{
+    Target& target = m_process->GetTarget();
+
+    SymbolContextList list;
+    if (!target.GetImages().FindSymbolsWithNameAndType (ConstString(name), eSymbolTypeAny, list))
+        return false;
+
+    Address address = list[0].symbol->GetAddress();
+    addr_t addr = address.GetLoadAddress (&target);
+    if (addr == LLDB_INVALID_ADDRESS)
+        return false;
+
+    Error error;
+    value = (uint32_t)m_process->ReadUnsignedIntegerFromMemory(addr + field*sizeof(uint32_t), sizeof(uint32_t), 0, error);
+    if (error.Fail())
+        return false;
+
+    if (field == eSize)
+        value /= 8; // convert bits to bytes
+
+    return true;
+}
+
+const DYLDRendezvous::ThreadInfo&
+DYLDRendezvous::GetThreadInfo()
+{
+    if (!m_thread_info.valid)
+    {
+        bool ok = true;
+
+        ok &= FindMetadata ("_thread_db_pthread_dtvp", eOffset, m_thread_info.dtv_offset);
+        ok &= FindMetadata ("_thread_db_dtv_dtv", eSize, m_thread_info.dtv_slot_size);
+        ok &= FindMetadata ("_thread_db_link_map_l_tls_modid", eOffset, m_thread_info.modid_offset);
+        ok &= FindMetadata ("_thread_db_dtv_t_pointer_val", eOffset, m_thread_info.tls_offset);
+
+        if (ok)
+            m_thread_info.valid = true;
+    }
+
+    return m_thread_info;
+}
+
 void
 DYLDRendezvous::DumpToLog(Log *log) const
 {
diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.h b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.h
index 5f8b013dd4a..ca008931799 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.h
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.h
@@ -48,6 +48,16 @@ class DYLDRendezvous {
     };
 
 public:
+    // Various metadata supplied by the inferior's threading library to describe
+    // the per-thread state.
+    struct ThreadInfo {
+        bool     valid;         // whether we read valid metadata
+        uint32_t dtv_offset;    // offset of DTV pointer within pthread
+        uint32_t dtv_slot_size; // size of one DTV slot
+        uint32_t modid_offset;  // offset of module ID within link_map
+        uint32_t tls_offset;    // offset of TLS pointer within DTV slot
+    };
+
     DYLDRendezvous(lldb_private::Process *process);
 
     /// Update the internal snapshot of runtime linker rendezvous and recompute
@@ -100,6 +110,10 @@ public:
     lldb::addr_t
     GetLDBase() const { return m_current.ldbase; }
 
+    /// @returns the thread layout metadata from the inferiors thread library.
+    const ThreadInfo&
+    GetThreadInfo();
+
     /// @returns true if modules have been loaded into the inferior since the
     /// last call to Resolve().
     bool
@@ -128,6 +142,7 @@ public:
     /// This object is a rough analogue to the struct link_map object which
     /// actually lives in the inferiors memory.
     struct SOEntry {
+        lldb::addr_t link_addr; ///< Address of this link_map.
         lldb::addr_t base_addr; ///< Base address of the loaded object.
         lldb::addr_t path_addr; ///< String naming the shared object.
         lldb::addr_t dyn_addr;  ///< Dynamic section of shared object.
@@ -142,6 +157,7 @@ public:
         }
 
         void clear() {
+            link_addr = 0;
             base_addr = 0;
             path_addr = 0;
             dyn_addr  = 0;
@@ -194,6 +210,9 @@ protected:
     /// Resolve().
     SOEntryList m_removed_soentries;
 
+    /// Threading metadata read from the inferior.
+    ThreadInfo  m_thread_info;
+
     /// Reads an unsigned integer of @p size bytes from the inferior's address
     /// space starting at @p addr.
     ///
@@ -232,6 +251,10 @@ protected:
     /// supplied by the runtime linker.
     bool
     TakeSnapshot(SOEntryList &entry_list);
+
+    enum PThreadField { eSize, eNElem, eOffset };
+
+    bool FindMetadata(const char *name, PThreadField field, uint32_t& value);
 };
 
 #endif
diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
index 8a0b194446c..cb7adc4f3ec 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
@@ -123,7 +123,7 @@ DynamicLoaderPOSIXDYLD::DidAttach()
     {
         ModuleList module_list;
         module_list.Append(executable);
-        UpdateLoadedSections(executable, load_offset);
+        UpdateLoadedSections(executable, LLDB_INVALID_ADDRESS, load_offset);
         LoadAllCurrentModules();
         m_process->GetTarget().ModulesDidLoad(module_list);
     }
@@ -144,7 +144,7 @@ DynamicLoaderPOSIXDYLD::DidLaunch()
     {
         ModuleList module_list;
         module_list.Append(executable);
-        UpdateLoadedSections(executable, load_offset);
+        UpdateLoadedSections(executable, LLDB_INVALID_ADDRESS, load_offset);
         ProbeEntry();
         m_process->GetTarget().ModulesDidLoad(module_list);
     }
@@ -209,13 +209,15 @@ DynamicLoaderPOSIXDYLD::CanLoadImage()
 }
 
 void
-DynamicLoaderPOSIXDYLD::UpdateLoadedSections(ModuleSP module, addr_t base_addr)
+DynamicLoaderPOSIXDYLD::UpdateLoadedSections(ModuleSP module, addr_t link_map_addr, addr_t base_addr)
 {
     SectionLoadList &load_list = m_process->GetTarget().GetSectionLoadList();
     const SectionList *sections = GetSectionListFromModule(module);
 
     assert(sections && "SectionList missing from loaded module.");
 
+    m_loaded_modules[module] = link_map_addr;
+
     const size_t num_sections = sections->GetSize();
 
     for (unsigned i = 0; i < num_sections; ++i)
@@ -243,6 +245,8 @@ DynamicLoaderPOSIXDYLD::UnloadSections(const ModuleSP module)
 
     assert(sections && "SectionList missing from unloaded module.");
 
+    m_loaded_modules.erase(module);
+
     const size_t num_sections = sections->GetSize();
     for (size_t i = 0; i < num_sections; ++i)
     {
@@ -337,7 +341,7 @@ DynamicLoaderPOSIXDYLD::RefreshModules()
         for (I = m_rendezvous.loaded_begin(); I != E; ++I)
         {
             FileSpec file(I->path.c_str(), true);
-            ModuleSP module_sp = LoadModuleAtAddress(file, I->base_addr);
+            ModuleSP module_sp = LoadModuleAtAddress(file, I->link_addr, I->base_addr);
             if (module_sp.get())
             {
                 loaded_modules.AppendIfNeeded(module_sp);
@@ -439,11 +443,17 @@ DynamicLoaderPOSIXDYLD::LoadAllCurrentModules()
         return;
     }
 
+    // The rendezvous class doesn't enumerate the main module, so track
+    // that ourselves here.
+    ModuleSP executable = GetTargetExecutable();
+    m_loaded_modules[executable] = m_rendezvous.GetLinkMapAddress();
+
+
     for (I = m_rendezvous.begin(), E = m_rendezvous.end(); I != E; ++I)
     {
         const char *module_path = I->path.c_str();
         FileSpec file(module_path, false);
-        ModuleSP module_sp = LoadModuleAtAddress(file, I->base_addr);
+        ModuleSP module_sp = LoadModuleAtAddress(file, I->link_addr, I->base_addr);
         if (module_sp.get())
         {
             module_list.Append(module_sp);
@@ -461,7 +471,7 @@ DynamicLoaderPOSIXDYLD::LoadAllCurrentModules()
 }
 
 ModuleSP
-DynamicLoaderPOSIXDYLD::LoadModuleAtAddress(const FileSpec &file, addr_t base_addr)
+DynamicLoaderPOSIXDYLD::LoadModuleAtAddress(const FileSpec &file, addr_t link_map_addr, addr_t base_addr)
 {
     Target &target = m_process->GetTarget();
     ModuleList &modules = target.GetImages();
@@ -470,11 +480,11 @@ DynamicLoaderPOSIXDYLD::LoadModuleAtAddress(const FileSpec &file, addr_t base_ad
     ModuleSpec module_spec (file, target.GetArchitecture());
     if ((module_sp = modules.FindFirstModule (module_spec))) 
     {
-        UpdateLoadedSections(module_sp, base_addr);
+        UpdateLoadedSections(module_sp, link_map_addr, base_addr);
     }
     else if ((module_sp = target.GetSharedModule(module_spec))) 
     {
-        UpdateLoadedSections(module_sp, base_addr);
+        UpdateLoadedSections(module_sp, link_map_addr, base_addr);
     }
 
     return module_sp;
@@ -537,3 +547,68 @@ DynamicLoaderPOSIXDYLD::GetSectionListFromModule(const ModuleSP module) const
     }
     return sections;
 }
+
+static int ReadInt(Process *process, addr_t addr)
+{
+    Error error;
+    int value = (int)process->ReadUnsignedIntegerFromMemory(addr, sizeof(uint32_t), 0, error);
+    if (error.Fail())
+        return -1;
+    else
+        return value;
+}
+
+static addr_t ReadPointer(Process *process, addr_t addr)
+{
+    Error error;
+    addr_t value = process->ReadPointerFromMemory(addr, error);
+    if (error.Fail())
+        return LLDB_INVALID_ADDRESS;
+    else
+        return value;
+}
+
+lldb::addr_t
+DynamicLoaderPOSIXDYLD::GetThreadLocalData (const lldb::ModuleSP module, const lldb::ThreadSP thread)
+{
+    std::map<ModuleWP, addr_t>::const_iterator it = m_loaded_modules.find (module);
+    if (it == m_loaded_modules.end())
+        return LLDB_INVALID_ADDRESS;
+
+    addr_t link_map = it->second;
+    if (link_map == LLDB_INVALID_ADDRESS)
+        return LLDB_INVALID_ADDRESS;
+
+    const DYLDRendezvous::ThreadInfo &metadata = m_rendezvous.GetThreadInfo();
+    if (!metadata.valid)
+        return LLDB_INVALID_ADDRESS;
+
+    // Get the thread pointer.
+    addr_t tp = thread->GetThreadPointer ();
+    if (tp == LLDB_INVALID_ADDRESS)
+        return LLDB_INVALID_ADDRESS;
+
+    // Find the module's modid.
+    int modid = ReadInt (m_process, link_map + metadata.modid_offset);
+    if (modid == -1)
+        return LLDB_INVALID_ADDRESS;
+
+    // Lookup the DTV stucture for this thread.
+    addr_t dtv_ptr = tp + metadata.dtv_offset;
+    addr_t dtv = ReadPointer (m_process, dtv_ptr);
+    if (dtv == LLDB_INVALID_ADDRESS)
+        return LLDB_INVALID_ADDRESS;
+
+    // Find the TLS block for this module.
+    addr_t dtv_slot = dtv + metadata.dtv_slot_size*modid;
+    addr_t tls_block = ReadPointer (m_process, dtv_slot + metadata.tls_offset);
+
+    Module *mod = module.get();
+    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
+    if (log)
+        log->Printf("DynamicLoaderPOSIXDYLD::Performed TLS lookup: "
+                    "module=%s, link_map=0x%" PRIx64 ", tp=0x%" PRIx64 ", modid=%i, tls_block=0x%" PRIx64 "\n",
+                    mod->GetObjectName().AsCString(""), link_map, tp, modid, tls_block);
+
+    return tls_block;
+}
diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
index 414f12098cf..7997b34195a 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
@@ -61,6 +61,9 @@ public:
     virtual lldb_private::Error
     CanLoadImage();
 
+    virtual lldb::addr_t
+    GetThreadLocalData (const lldb::ModuleSP module, const lldb::ThreadSP thread);
+
     //------------------------------------------------------------------
     // PluginInterface protocol
     //------------------------------------------------------------------
@@ -95,6 +98,9 @@ protected:
     /// Rendezvous breakpoint.
     lldb::break_id_t m_dyld_bid;
 
+    /// Loaded module list. (link map for each module)
+    std::map<lldb::ModuleWP, lldb::addr_t, std::owner_less<lldb::ModuleWP>> m_loaded_modules;
+
     /// Enables a breakpoint on a function called by the runtime
     /// linker each time a module is loaded or unloaded.
     void
@@ -117,10 +123,13 @@ protected:
     ///
     /// @param module The module to traverse.
     ///
+    /// @param link_map_addr The virtual address of the link map for the @p module.
+    ///
     /// @param base_addr The virtual base address @p module is loaded at.
     void
-    UpdateLoadedSections(lldb::ModuleSP module, 
-                         lldb::addr_t base_addr = 0);
+    UpdateLoadedSections(lldb::ModuleSP module,
+                         lldb::addr_t link_map_addr,
+                         lldb::addr_t base_addr);
 
     /// Removes the loaded sections from the target in @p module.
     ///
@@ -131,7 +140,7 @@ protected:
     /// Locates or creates a module given by @p file and updates/loads the
     /// resulting module at the virtual base address @p base_addr.
     lldb::ModuleSP
-    LoadModuleAtAddress(const lldb_private::FileSpec &file, lldb::addr_t base_addr);
+    LoadModuleAtAddress(const lldb_private::FileSpec &file, lldb::addr_t link_map_addr, lldb::addr_t base_addr);
 
     /// Resolves the entry point for the current inferior process and sets a
     /// breakpoint at that address.