1 files changed, 91 insertions, 0 deletions
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index a0cda3485c6..bda0cb33097 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -19,6 +19,7 @@
 #include <sys/socket.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
+#include <sys/user.h>
 #include <sys/wait.h>
 
 // C++ Includes
@@ -46,6 +47,19 @@
 #ifndef PTRACE_SETREGSET
   #define PTRACE_SETREGSET 0x4205
 #endif
+#ifndef PTRACE_GET_THREAD_AREA
+  #define PTRACE_GET_THREAD_AREA 25
+#endif
+#ifndef PTRACE_ARCH_PRCTL
+  #define PTRACE_ARCH_PRCTL      30
+#endif
+#ifndef ARCH_GET_FS
+  #define ARCH_SET_GS 0x1001
+  #define ARCH_SET_FS 0x1002
+  #define ARCH_GET_FS 0x1003
+  #define ARCH_GET_GS 0x1004
+#endif
+
 
 // Support hardware breakpoints in case it has not been defined
 #ifndef TRAP_HWBKPT
@@ -703,6 +717,74 @@ WriteRegisterSetOperation::Execute(ProcessMonitor *monitor)
 }
 
 //------------------------------------------------------------------------------
+/// @class ReadThreadPointerOperation
+/// @brief Implements ProcessMonitor::ReadThreadPointer.
+class ReadThreadPointerOperation : public Operation
+{
+public:
+    ReadThreadPointerOperation(lldb::tid_t tid, lldb::addr_t *addr, bool &result)
+        : m_tid(tid), m_addr(addr), m_result(result)
+        { }
+
+    void Execute(ProcessMonitor *monitor);
+
+private:
+    lldb::tid_t m_tid;
+    lldb::addr_t *m_addr;
+    bool &m_result;
+};
+
+void
+ReadThreadPointerOperation::Execute(ProcessMonitor *monitor)
+{
+    Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (POSIX_LOG_REGISTERS));
+    if (log)
+        log->Printf ("ProcessMonitor::%s()", __FUNCTION__);
+
+    // The process for getting the thread area on Linux is
+    // somewhat... obscure. There's several different ways depending on
+    // what arch you're on, and what kernel version you have.
+
+    const ArchSpec& arch = monitor->GetProcess().GetTarget().GetArchitecture();
+    switch(arch.GetMachine())
+    {
+    case llvm::Triple::x86:
+    {
+        // Find the GS register location for our host architecture.
+        size_t gs_user_offset = offsetof(struct user, regs);
+#ifdef __x86_64__
+        gs_user_offset += offsetof(struct user_regs_struct, gs);
+#endif
+#ifdef __i386__
+        gs_user_offset += offsetof(struct user_regs_struct, xgs);
+#endif
+
+        // Read the GS register value to get the selector.
+        errno = 0;
+        long gs = PTRACE(PTRACE_PEEKUSER, m_tid, (void*)gs_user_offset, NULL, 0);
+        if (errno)
+        {
+            m_result = false;
+            break;
+        }
+
+        // Read the LDT base for that selector.
+        uint32_t tmp[4];
+        m_result = (PTRACE(PTRACE_GET_THREAD_AREA, m_tid, (void *)(gs >> 3), &tmp, 0) == 0);
+        *m_addr = tmp[1];
+        break;
+    }
+    case llvm::Triple::x86_64:
+        // Read the FS register base.
+        m_result = (PTRACE(PTRACE_ARCH_PRCTL, m_tid, m_addr, (void *)ARCH_GET_FS, 0) == 0);
+        break;
+    default:
+        m_result = false;
+        break;
+    }
+}
+
+//------------------------------------------------------------------------------
 /// @class ResumeOperation
 /// @brief Implements ProcessMonitor::Resume.
 class ResumeOperation : public Operation
@@ -2106,6 +2188,15 @@ ProcessMonitor::WriteRegisterSet(lldb::tid_t tid, void *buf, size_t buf_size, un
 }
 
 bool
+ProcessMonitor::ReadThreadPointer(lldb::tid_t tid, lldb::addr_t &value)
+{
+    bool result;
+    ReadThreadPointerOperation op(tid, &value, result);
+    DoOperation(&op);
+    return result;
+}
+
+bool
 ProcessMonitor::Resume(lldb::tid_t tid, uint32_t signo)
 {
     bool result;