def setup_root_stack():
# The gcmap table is a list of pairs of pointers:
# void *SafePointAddress;
# void *Shape;
# Here, i.e. when the program starts, we sort it
# in-place on the SafePointAddress to allow for more
# efficient searches.
gcmapstart = llop.llvm_gcmapstart(llmemory.Address)
gcmapend = llop.llvm_gcmapend(llmemory.Address)
insertion_sort(gcmapstart, gcmapend)
def walk_to_parent_frame(self, callee, caller):
"""Starting from 'callee', walk the next older frame on the stack
and fill 'caller' accordingly. Also invokes the collect_stack_root()
callback from the GC code for each GC root found in 'caller'.
"""
#
# The gcmap table is a list of entries, two machine words each:
# void *SafePointAddress;
# int Shape;
#
# A "safe point" is the return address of a call.
# The "shape" of a safe point is a list of integers
# that represent "locations". A "location" can be
# either in the stack or in a register. See
# getlocation() for the decoding of this integer.
# The locations stored in a "shape" are as follows:
#
# * The "location" of the return address. This is just
# after the end of the frame of 'callee'; it is the
# first word of the frame of 'caller' (see picture
# below).
#
# * Four "locations" that specify where the function saves
# each of the four callee-saved registers (%ebx, %esi,
# %edi, %ebp).
#
# * The number of live GC roots around the call.
#
# * For each GC root, an integer that specify where the
# GC pointer is stored. This is a "location" too.
#
# XXX the details are completely specific to X86!!!
# a picture of the stack may help:
# ^ ^ ^
# | ... | to older frames
# +--------------+
# | ret addr | <------ caller_frame (addr of retaddr)
# | ... |
# | caller frame |
# | ... |
# +--------------+
# | ret addr | <------ callee_frame (addr of retaddr)
# | ... |
# | callee frame |
# | ... | lower addresses
# +--------------+ v v v
#
retaddr = callee.frame_address.address[0]
#
# try to locate the caller function based on retaddr.
#
gcmapstart = llop.llvm_gcmapstart(llmemory.Address)
gcmapend = llop.llvm_gcmapend(llmemory.Address)
item = search_in_gcmap(gcmapstart, gcmapend, retaddr)
if not item:
# the item may have been not found because the array was
# not sorted. Sort it and try again.
sort_gcmap(gcmapstart, gcmapend)
item = search_in_gcmap(gcmapstart, gcmapend, retaddr)
if not item:
llop.debug_fatalerror(lltype.Void, "cannot find gc roots!")
return False
#
# found! Enumerate the GC roots in the caller frame
#
shape = item.signed[1]
if shape < 0:
shape = ~ shape # can ignore this "range" marker here
self._shape_decompressor.setpos(shape)
collect_stack_root = self.gcdata._gc_collect_stack_root
gc = self.gc
while True:
location = self._shape_decompressor.next()
if location == 0:
break
addr = self.getlocation(callee, location)
if addr.address[0] != llmemory.NULL:
collect_stack_root(gc, addr)
#
# track where the caller_frame saved the registers from its own
# caller
#
reg = CALLEE_SAVED_REGS - 1
while reg >= 0:
location = self._shape_decompressor.next()
addr = self.getlocation(callee, location)
caller.regs_stored_at[reg] = addr
reg -= 1
location = self._shape_decompressor.next()
caller.frame_address = self.getlocation(callee, location)
# we get a NULL marker to mean "I'm the frame
# of the entry point, stop walking"
return caller.frame_address != llmemory.NULL
def walk_to_parent_frame(self):
#
# The gcmap table is a list of pairs of pointers:
# void *SafePointAddress;
# void *Shape;
#
# A "safe point" is the return address of a call.
# The "shape" of a safe point records the size of the
# frame of the function containing it, as well as a
# list of the variables that contain gc roots at that
# time. Each variable is described by its offset in
# the frame.
#
callee_frame = self.stack_current
if llmemory.cast_adr_to_int(callee_frame) & 1:
return False # odd bit set here when the callee_frame
# is the frame of main(), i.e. when there
# is nothing more for us in the stack.
#
# XXX the details are completely specific to X86!!!
# a picture of the stack may help:
# ^ ^ ^
# | ... | to older frames
# +--------------+
# | first word | <------ caller_frame (addr of 1st word)
# + +
# | caller frame |
# | ... |
# | frame data | <------ frame_data_base
# +--------------+
# | ret addr |
# +--------------+
# | first word | <------ callee_frame (addr of 1st word)
# + +
# | callee frame |
# | ... |
# | frame data | lower addresses
# +--------------+ v v v
#
retaddr = callee_frame.address[1]
#
# try to locate the caller function based on retaddr.
#
gcmapstart = llop.llvm_gcmapstart(llmemory.Address)
gcmapend = llop.llvm_gcmapend(llmemory.Address)
item = binary_search(gcmapstart, gcmapend, retaddr)
if item.address[0] == retaddr:
#
# found! Setup pointers allowing us to
# parse the caller's frame structure...
#
shape = item.address[1]
# XXX assumes that .signed is 32-bit
framesize = shape.signed[0] # odd if it's main()
livecount = shape.signed[1]
caller_frame = callee_frame + 4 + framesize
self.stack_current = caller_frame
self.frame_data_base = callee_frame + 8
self.remaining_roots_in_current_frame = livecount
self.liveoffsets = shape + 8
return True
# retaddr not found!
llop.debug_fatalerror(lltype.Void, "cannot find gc roots!")
return False
def walk_to_parent_frame(self, callee, caller):
"""Starting from 'callee', walk the next older frame on the stack
and fill 'caller' accordingly. Also invokes the collect_stack_root()
callback from the GC code for each GC root found in 'caller'.
"""
#
# The gcmap table is a list of entries, two machine words each:
# void *SafePointAddress;
# int Shape;
#
# A "safe point" is the return address of a call.
# The "shape" of a safe point is a list of integers
# that represent "locations". A "location" can be
# either in the stack or in a register. See
# getlocation() for the decoding of this integer.
# The locations stored in a "shape" are as follows:
#
# * The "location" of the return address. This is just
# after the end of the frame of 'callee'; it is the
# first word of the frame of 'caller' (see picture
# below).
#
# * Four "locations" that specify where the function saves
# each of the four callee-saved registers (%ebx, %esi,
# %edi, %ebp).
#
# * The number of live GC roots around the call.
#
# * For each GC root, an integer that specify where the
# GC pointer is stored. This is a "location" too.
#
# XXX the details are completely specific to X86!!!
# a picture of the stack may help:
# ^ ^ ^
# | ... | to older frames
# +--------------+
# | ret addr | <------ caller_frame (addr of retaddr)
# | ... |
# | caller frame |
# | ... |
# +--------------+
# | ret addr | <------ callee_frame (addr of retaddr)
# | ... |
# | callee frame |
# | ... | lower addresses
# +--------------+ v v v
#
retaddr = callee.frame_address.address[0]
#
# try to locate the caller function based on retaddr.
#
gcmapstart = llop.llvm_gcmapstart(llmemory.Address)
gcmapend = llop.llvm_gcmapend(llmemory.Address)
item = search_in_gcmap(gcmapstart, gcmapend, retaddr)
if not item:
# the item may have been not found because the array was
# not sorted. Sort it and try again.
sort_gcmap(gcmapstart, gcmapend)
item = search_in_gcmap(gcmapstart, gcmapend, retaddr)
if not item:
llop.debug_fatalerror(lltype.Void, "cannot find gc roots!")
return False
#
# found! Enumerate the GC roots in the caller frame
#
shape = item.signed[1]
if shape < 0:
shape = ~shape # can ignore this "range" marker here
self._shape_decompressor.setpos(shape)
collect_stack_root = self.gcdata._gc_collect_stack_root
gc = self.gc
while True:
location = self._shape_decompressor.next()
if location == 0:
break
addr = self.getlocation(callee, location)
if addr.address[0] != llmemory.NULL:
collect_stack_root(gc, addr)
#
# track where the caller_frame saved the registers from its own
# caller
#
reg = CALLEE_SAVED_REGS - 1
while reg >= 0:
location = self._shape_decompressor.next()
addr = self.getlocation(callee, location)
caller.regs_stored_at[reg] = addr
reg -= 1
location = self._shape_decompressor.next()
caller.frame_address = self.getlocation(callee, location)
# we get a NULL marker to mean "I'm the frame
# of the entry point, stop walking"
return caller.frame_address != llmemory.NULL