Allow installing watchpoints at less than 8-byte alligned addresses for AArch64 targets

This patch allows LLDB for AArch64 to watch all bytes, words or double words individually on non 8-byte alligned addresses.

This patch also adds tests to verify this functionality.

Differential revision: http://reviews.llvm.org/D21280

llvm-svn: 272916
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
index a09018e..f636511 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
@@ -566,6 +566,7 @@
         return LLDB_INVALID_INDEX32;
 		
     uint32_t control_value = 0, wp_index = 0;
+    lldb::addr_t real_addr = addr;
 
     // Check if we are setting watchpoint other than read/write/access
     // Also update watchpoint flag to match AArch64 write-read bit configuration.
@@ -588,9 +589,23 @@
         return LLDB_INVALID_INDEX32;
 
     // Check 8-byte alignment for hardware watchpoint target address.
-    // TODO: Add support for watching un-aligned addresses
+    // Below is a hack to recalculate address and size in order to
+    // make sure we can watch non 8-byte alligned addresses as well.
     if (addr & 0x07)
-        return LLDB_INVALID_INDEX32;
+    {
+        uint8_t watch_mask = (addr & 0x07) + size;
+
+        if (watch_mask > 0x08)
+            return LLDB_INVALID_INDEX32;
+        else if (watch_mask <= 0x02)
+            size = 2;
+        else if (watch_mask <= 0x04)
+            size = 4;
+        else
+            size = 8;
+
+        addr = addr & (~0x07);
+    }
 
     // Setup control value
     control_value = watch_flags << 3;
@@ -620,6 +635,7 @@
     if ((m_hwp_regs[wp_index].control & 1) == 0)
     {
         // Update watchpoint in local cache
+        m_hwp_regs[wp_index].real_addr = real_addr;
         m_hwp_regs[wp_index].address = addr;
         m_hwp_regs[wp_index].control = control_value;
         m_hwp_regs[wp_index].refcount = 1;
@@ -801,6 +817,7 @@
         if (m_hwp_regs[wp_index].refcount >= 1 && WatchpointIsEnabled(wp_index)
             && trap_addr >= watch_addr && trap_addr < watch_addr + watch_size)
         {
+            m_hwp_regs[wp_index].hit_addr = trap_addr;
             return Error();
         }
     }
@@ -821,7 +838,24 @@
         return LLDB_INVALID_ADDRESS;
 
     if (WatchpointIsEnabled(wp_index))
-        return m_hwp_regs[wp_index].address;
+        return m_hwp_regs[wp_index].real_addr;
+    else
+        return LLDB_INVALID_ADDRESS;
+}
+
+lldb::addr_t
+NativeRegisterContextLinux_arm64::GetWatchpointHitAddress (uint32_t wp_index)
+{
+    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_WATCHPOINTS));
+
+    if (log)
+        log->Printf ("NativeRegisterContextLinux_arm64::%s()", __FUNCTION__);
+
+    if (wp_index >= m_max_hwp_supported)
+        return LLDB_INVALID_ADDRESS;
+
+    if (WatchpointIsEnabled(wp_index))
+        return m_hwp_regs[wp_index].hit_addr;
     else
         return LLDB_INVALID_ADDRESS;
 }
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
index c60baa6..4d9a990 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
@@ -74,6 +74,9 @@
         GetWatchpointHitIndex(uint32_t &wp_index, lldb::addr_t trap_addr) override;
 
         lldb::addr_t
+        GetWatchpointHitAddress (uint32_t wp_index) override;
+
+        lldb::addr_t
         GetWatchpointAddress (uint32_t wp_index) override;
 
         uint32_t
@@ -161,6 +164,8 @@
         struct DREG
         {
             lldb::addr_t address;  // Breakpoint/watchpoint address value.
+            lldb::addr_t hit_addr; // Address at which last watchpoint trigger exception occurred.
+            lldb::addr_t real_addr;  // Address value that should cause target to stop.
             uint32_t control;  // Breakpoint/watchpoint control value.
             uint32_t refcount;  // Serves as enable/disable and refernce counter.
         };
diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
index f1212ae..13db5ce 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
@@ -2059,7 +2059,8 @@
                             {
                                 WatchpointSP wp_sp;
                                 ArchSpec::Core core = GetTarget().GetArchitecture().GetCore();
-                                if (core >= ArchSpec::kCore_mips_first && core <= ArchSpec::kCore_mips_last)
+                                if ((core >= ArchSpec::kCore_mips_first && core <= ArchSpec::kCore_mips_last) ||
+                                    (core >= ArchSpec::eCore_arm_arm64 && core <= ArchSpec::eCore_arm_aarch64))
                                     wp_sp = GetTarget().GetWatchpointList().FindByAddress(wp_hit_addr);
                                 if (!wp_sp)
                                     wp_sp = GetTarget().GetWatchpointList().FindByAddress(wp_addr);