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