FreeBSD hardware watchpoint implementation

Implement x86_64 debug register read/write in support of hardware
watchpoints. Hoist LinuxThread::TraceNotify code back into
POSIXThread::TraceNotify()

Patch by John Wolfe.

We still need to rework this later to avoid the #ifdef FreeBSD.

llvm-reviews.chandlerc.com/D2572
llvm.org/pr16706

llvm-svn: 201706

5 files changed, 70 insertions, 5 deletions

diff --git a/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp b/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
index 8d4c71ff269..cc759eaad96 100644
--- a/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
+++ b/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
@@ -65,7 +65,16 @@ POSIXThread::POSIXThread(Process &process, lldb::tid_t tid)
         lldb::WatchpointSP wp = wp_list.GetByIndex(wp_idx);
         if (wp.get() && wp->IsEnabled())
         {
-            assert(EnableHardwareWatchpoint(wp.get()));
+            // This watchpoint as been enabled; obviously this "new" thread
+            // has been created since that watchpoint was enabled.  Since
+            // the POSIXBreakpointProtocol has yet to be initialized, its
+            // m_watchpoints_initialized member will be FALSE.  Attempting to
+            // read the debug status register to determine if a watchpoint
+            // has been hit would result in the zeroing of that register.
+            // Since the active debug registers would have been cloned when
+            // this thread was created, simply force the m_watchpoints_initized
+            // member to TRUE and avoid resetting dr6 and dr7.
+            GetPOSIXBreakpointProtocol()->ForceWatchpointsInitialized();
         }
     }
 }
@@ -509,6 +518,21 @@ POSIXThread::WatchNotify(const ProcessMessage &message)
 void
 POSIXThread::TraceNotify(const ProcessMessage &message)
 {
+    POSIXBreakpointProtocol* reg_ctx = GetPOSIXBreakpointProtocol();
+    if (reg_ctx)
+    {
+        uint32_t num_hw_wps = reg_ctx->NumSupportedHardwareWatchpoints();
+        uint32_t wp_idx;
+        for (wp_idx = 0; wp_idx < num_hw_wps; wp_idx++)
+        {
+            if (reg_ctx->IsWatchpointHit(wp_idx))
+            {
+                WatchNotify(message);
+                return;
+            }
+        }
+    }
+
     SetStopInfo (StopInfo::CreateStopReasonToTrace(*this));
 }
 
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_i386.cpp b/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_i386.cpp
index 50ec8d414a1..01c9bb4cde8 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_i386.cpp
+++ b/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_i386.cpp
@@ -37,8 +37,18 @@ struct GPR
     uint32_t gs;
 };
 
-#define DR_SIZE 0
-#define DR_OFFSET(reg_index) 0
+struct dbreg {
+    uint32_t  dr[8];     /* debug registers */
+                         /* Index 0-3: debug address registers */
+                         /* Index 4-5: reserved */
+                         /* Index 6: debug status */
+                         /* Index 7: debug control */
+};
+
+
+#define DR_SIZE sizeof(uint32_t)
+#define DR_OFFSET(reg_index) \
+    (LLVM_EXTENSION offsetof(dbreg, dr[reg_index]))
 
 //---------------------------------------------------------------------------
 // Include RegisterInfos_i386 to declare our g_register_infos_i386 structure.
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_x86_64.cpp b/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_x86_64.cpp
index 471734580ff..2162aaffff1 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_x86_64.cpp
+++ b/lldb/source/Plugins/Process/POSIX/RegisterContextFreeBSD_x86_64.cpp
@@ -46,8 +46,19 @@ typedef struct _GPR
     uint64_t ss;
 } GPR;
 
-#define DR_SIZE 0
-#define DR_OFFSET(reg_index) 0
+struct dbreg {
+       uint64_t  dr[16];  /* debug registers */
+                          /* Index 0-3: debug address registers */
+                          /* Index 4-5: reserved */
+                          /* Index 6: debug status */
+                          /* Index 7: debug control */
+                          /* Index 8-15: reserved */
+};
+
+#define DR_SIZE sizeof(uint64_t)
+#define DR_OFFSET(reg_index) \
+    (LLVM_EXTENSION offsetof(dbreg, dr[reg_index]))
+
 
 //---------------------------------------------------------------------------
 // Include RegisterInfos_x86_64 to declare our g_register_infos_x86_64 structure.
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIX.h b/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIX.h
index e48c528403e..600dae73b5b 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIX.h
+++ b/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIX.h
@@ -66,6 +66,10 @@ public:
     virtual uint32_t
     NumSupportedHardwareWatchpoints () = 0;
 
+    // Force m_watchpoints_initialized to TRUE
+    void
+    ForceWatchpointsInitialized () {m_watchpoints_initialized = true;}
+
 protected:
     bool m_watchpoints_initialized;
 };
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIXProcessMonitor_x86.cpp b/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIXProcessMonitor_x86.cpp
index f833c9b4752..c446bbfa7dc 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIXProcessMonitor_x86.cpp
+++ b/lldb/source/Plugins/Process/POSIX/RegisterContextPOSIXProcessMonitor_x86.cpp
@@ -109,6 +109,15 @@ RegisterContextPOSIXProcessMonitor_x86_64::ReadRegister(const unsigned reg,
                                                         RegisterValue &value)
 {
     ProcessMonitor &monitor = GetMonitor();
+
+#if defined(__FreeBSD__)
+    if (reg >= m_reg_info.first_dr)
+        return monitor.ReadDebugRegisterValue(m_thread.GetID(),
+                                              GetRegisterOffset(reg),
+                                              GetRegisterName(reg),
+                                              GetRegisterSize(reg),
+                                              value);
+#endif
     return monitor.ReadRegisterValue(m_thread.GetID(),
                                      GetRegisterOffset(reg),
                                      GetRegisterName(reg),
@@ -164,6 +173,13 @@ RegisterContextPOSIXProcessMonitor_x86_64::WriteRegister(const unsigned reg,
     }
 
     ProcessMonitor &monitor = GetMonitor();
+#if defined(__FreeBSD__)
+    if (reg >= m_reg_info.first_dr)
+        return monitor.WriteDebugRegisterValue(m_thread.GetID(),
+                                               GetRegisterOffset(reg_to_write),
+                                               GetRegisterName(reg_to_write),
+                                               value_to_write);
+#endif
     return monitor.WriteRegisterValue(m_thread.GetID(),
                                       GetRegisterOffset(reg_to_write),
                                       GetRegisterName(reg_to_write),