Implement software breakpoints for arm in Linux platform.

[sas]

Summary

This change adds the list of software breakpoints for Linux-arm targets. The opcodes used are different from what is specified by ARM because the linux kernel expects something slightly different. The relevant code in the kernel can be found here: https://github.com/torvalds/linux/blob/master/arch/arm/kernel/ptrace.c#L223

[jasonmolenda]

This looks good to me but yeah, we should prob wait for Todd to sign off on it before committing.

[sas]

Ping.

[jasonmolenda]

I think Todd is a little busy with non-lldb stuff right now. I've reviewed this.

[jasonmolenda]

Landed in r220762.

[sas]

Thanks Jason.

source/Plugins/Platform/Linux/PlatformLinux.cpp

 #include <stdio.h>
 #ifndef LLDB_DISABLE_POSIX
 #include <sys/utsname.h>
 #endif
 
 // C++ Includes
 // Other libraries and framework includes
 // Project includes
+#include "lldb/Breakpoint/BreakpointLocation.h"
 #include "lldb/Core/Debugger.h"
 #include "lldb/Core/Error.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleList.h"
 #include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/State.h"
case llvm::Triple::x86_64:
         break;
     case llvm::Triple::hexagon:
         {
             static const uint8_t g_hex_opcode[] = { 0x0c, 0xdb, 0x00, 0x54 };
             trap_opcode = g_hex_opcode;
             trap_opcode_size = sizeof(g_hex_opcode);
         }
         break;
+    case llvm::Triple::arm:
+        {
+            // The ARM reference recommends the use of 0xe7fddefe and 0xdefe
+            // but the linux kernel does otherwise.
+            static const uint8_t g_arm_breakpoint_opcode[] = { 0xf0, 0x01, 0xf0, 0xe7 };
+            static const uint8_t g_thumb_breakpoint_opcode[] = { 0x01, 0xde };
+
+            lldb::BreakpointLocationSP bp_loc_sp (bp_site->GetOwnerAtIndex (0));
+            AddressClass addr_class = eAddressClassUnknown;
+
+            if (bp_loc_sp)
+                addr_class = bp_loc_sp->GetAddress ().GetAddressClass ();
+
+            if (addr_class == eAddressClassCodeAlternateISA ||
+                    (addr_class == eAddressClassUnknown &&
+                     bp_loc_sp->GetAddress().GetOffset() & 1))
+            {
+                trap_opcode = g_thumb_breakpoint_opcode;
+                trap_opcode_size = sizeof(g_thumb_breakpoint_opcode);
+            }
+            else
+            {
+                trap_opcode = g_arm_breakpoint_opcode;
+                trap_opcode_size = sizeof(g_arm_breakpoint_opcode);
+            }
+        }
+        break;
     }
 
     if (bp_site->SetTrapOpcode(trap_opcode, trap_opcode_size))
         return trap_opcode_size;
     return 0;
 }
 
 int32_t