Fix unwinders on aarch64

Summary:
With a new enough version of gdb, we have a gdb.unwind module on
aarch64, so fix our unwinder to do the right thing.

Reviewed By: mxw

Differential Revision: D7202225

fbshipit-source-id: cfee595e7950fefb12e04eb2f93dc0041eb4f79a

hphp/tools/gdb/stack.py

@@ -74,9 +74,11 @@ def invoke(self, args, from_tty):
             print('walkstk: Cannot find any frames: corrupt stack?')
             return
 
+        arch = native_frame.architecture().name()
+        frame_reg = 'x29' if arch == 'aarch64' else 'rbp'
         # Set fp = $rbp, rip = $rip.
         fp_type = T('uintptr_t').pointer()
-        fp = native_frame.read_register('rbp').cast(fp_type)
+        fp = native_frame.read_register(frame_reg).cast(fp_type)
         rip = native_frame.pc()
 
         if len(argv) == 1:
@@ -193,14 +195,19 @@ def invoke(self, args, from_tty):
             return
 
         fp_type = T('uintptr_t').pointer()
-        fp = gdb.parse_and_eval('$rbp').cast(fp_type)
-        rip = gdb.parse_and_eval('$rip').cast(T('uintptr_t'))
 
-        if len(argv) >= 1:
-            fp = argv[0].cast(fp_type)
+        try:
+            arch = gdb.newest_frame().architecture().name()
+        except:
+            arch = 'i386:x86-64'
 
-            if len(argv) == 2:
-                rip = argv[1].cast(T('uintptr_t'))
+        frame_reg = '$x29' if arch == 'aarch64' else '$rbp'
+        pc_reg = '$pc' if arch == 'aarch64' else '$rip'
+
+        fp = (argv[0] if len(argv) >= 1 else
+              gdb.parse_and_eval(frame_reg)).cast(fp_type)
+        rip = (argv[1] if len(argv) == 2 else
+               gdb.parse_and_eval(pc_reg)).cast(T('uintptr_t'))
 
         i = 0
         fp = (fp, rip)

hphp/tools/gdb/unwind.py

@@ -26,12 +26,20 @@ class HHVMUnwinder(Unwinder):
 """
 
     def __init__(self):
+        try:
+            self.arch = gdb.newest_frame().architecture().name()
+        except:
+            self.arch = 'i386:x86-64'
+
+        self.frame_reg = 'x29' if self.arch == 'aarch64' else 'rbp'
+        self.stack_reg = 'sp' if self.arch == 'aarch64' else 'rsp'
+        self.pc_reg = 'pc' if self.arch == 'aarch64' else 'rip'
         super(HHVMUnwinder, self).__init__('hhvm_unwinder')
 
     def __call__(self, pending_frame):
-        fp = pending_frame.read_register('rbp')
-        sp = pending_frame.read_register('rsp')
-        ip = pending_frame.read_register('rip')
+        fp = pending_frame.read_register(self.frame_reg)
+        sp = pending_frame.read_register(self.stack_reg)
+        ip = pending_frame.read_register(self.pc_reg)
 
         if not frame.is_jitted(fp, ip):
             return None
@@ -50,18 +58,18 @@ def __call__(self, pending_frame):
 
         # Restore the saved frame pointer and instruction pointer.
         fp = fp.cast(T('uintptr_t').pointer())
-        unwind_info.add_saved_register('rbp', fp[0])
-        unwind_info.add_saved_register('rip', fp[1])
+        unwind_info.add_saved_register(self.frame_reg, fp[0])
+        unwind_info.add_saved_register(self.pc_reg, fp[1])
 
         if frame.is_jitted(fp[0], fp[1]):
             # Our parent frame is jitted.  Again, we are unable to track %rsp
             # properly in the TC, so just preserve its value (just as we do in
             # the TC's custom .eh_frame section).
-            unwind_info.add_saved_register('rsp', sp)
+            unwind_info.add_saved_register(self.stack_reg, sp)
         else:
             # Our parent frame is not jitted, so we're in enterTCHelper, and we
             # can restore our parent's %rsp as usual.
-            unwind_info.add_saved_register('rsp', fp + 16)
+            unwind_info.add_saved_register(self.stack_reg, fp + 16)
 
         return unwind_info