Changes for Bug 17384

Summary:
Virtual dynamic shared objects, or vdso files were 
not loaded for Linux OS.In Bug 17384 the call 
stack could not be unwinded from functions
residing in the vdso object.

This commit adds support for loading such files by
reading the Aux vectors since a vdso is invisibily 
mapped to the inferiors address space and the
 actual file is not present in the filesystem. The 
presence of the vdso is detected by inspecting 
the Aux vector for AT_SYSINFO_EHDR tag.

Reviewers: lldb-commits, ovyalov, tberghammer

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D14118

llvm-svn: 251505

2 files changed, 33 insertions, 2 deletions

diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
index e563ad66b4a..6ba7b470d74 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
@@ -91,7 +91,8 @@ DynamicLoaderPOSIXDYLD::DynamicLoaderPOSIXDYLD(Process *process)
       m_load_offset(LLDB_INVALID_ADDRESS),
       m_entry_point(LLDB_INVALID_ADDRESS),
       m_auxv(),
-      m_dyld_bid(LLDB_INVALID_BREAK_ID)
+      m_dyld_bid(LLDB_INVALID_BREAK_ID),
+      m_vdso_base(LLDB_INVALID_ADDRESS)
 {
 }
 
@@ -126,6 +127,8 @@ DynamicLoaderPOSIXDYLD::DidAttach()
     if (log)
         log->Printf ("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " executable '%s', load_offset 0x%" PRIx64, __FUNCTION__, m_process ? m_process->GetID () : LLDB_INVALID_PROCESS_ID, executable_sp ? executable_sp->GetFileSpec().GetPath().c_str () : "<null executable>", load_offset);
 
+    EvalVdsoStatus();
+
     // if we dont have a load address we cant re-base
     bool rebase_exec = (load_offset == LLDB_INVALID_ADDRESS) ? false : true;
 
@@ -213,6 +216,7 @@ DynamicLoaderPOSIXDYLD::DidLaunch()
 
     executable = GetTargetExecutable();
     load_offset = ComputeLoadOffset();
+    EvalVdsoStatus();
 
     if (executable.get() && load_offset != LLDB_INVALID_ADDRESS)
     {
@@ -503,7 +507,15 @@ DynamicLoaderPOSIXDYLD::LoadAllCurrentModules()
     // that ourselves here.
     ModuleSP executable = GetTargetExecutable();
     m_loaded_modules[executable] = m_rendezvous.GetLinkMapAddress();
-
+    if (m_vdso_base != LLDB_INVALID_ADDRESS)
+    {
+        FileSpec file_spec("[vdso]", false);
+        ModuleSP module_sp = LoadModuleAtAddress(file_spec, LLDB_INVALID_ADDRESS, m_vdso_base, false);
+        if (module_sp.get())
+        {
+            module_list.Append(module_sp);
+        }
+    }
     for (I = m_rendezvous.begin(), E = m_rendezvous.end(); I != E; ++I)
     {
         ModuleSP module_sp = LoadModuleAtAddress(I->file_spec, I->link_addr, I->base_addr, true);
@@ -551,6 +563,16 @@ DynamicLoaderPOSIXDYLD::ComputeLoadOffset()
     return m_load_offset;
 }
 
+void
+DynamicLoaderPOSIXDYLD::EvalVdsoStatus()
+{
+    AuxVector::iterator I = m_auxv->FindEntry(AuxVector::AT_SYSINFO_EHDR);
+
+    if (I != m_auxv->end())
+        m_vdso_base = I->value;
+
+}
+
 addr_t
 DynamicLoaderPOSIXDYLD::GetEntryPoint()
 {
diff --git a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
index d3407eb23cd..cb97bbf43ba 100644
--- a/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
+++ b/lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h
@@ -88,6 +88,10 @@ protected:
     /// Rendezvous breakpoint.
     lldb::break_id_t m_dyld_bid;
 
+    /// Contains AT_SYSINFO_EHDR, which means a vDSO has been
+    /// mapped to the address space
+    lldb::addr_t m_vdso_base;
+
     /// Loaded module list. (link map for each module)
     std::map<lldb::ModuleWP, lldb::addr_t, std::owner_less<lldb::ModuleWP>> m_loaded_modules;
 
@@ -159,6 +163,11 @@ protected:
     lldb::addr_t
     GetEntryPoint();
 
+    /// Evaluate if Aux vectors contain vDSO information
+    /// in case they do, read and assign the address to m_vdso_base
+    void
+    EvalVdsoStatus();
+
     /// Loads Module from inferior process.
     void
     ResolveExecutableModule(lldb::ModuleSP &module_sp);