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compute and display stack high water mark in 'freertos task' (GCC-312) #4

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compute and display stack high water mark in 'freertos task' (GCC-312) #4

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49 changes: 49 additions & 0 deletions freertos_gdb/task.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ class TaskProperty(StructProperty):
MUTEXES_HELD = ('', 'uxMutexesHeld', 'get_val')
SS = ('Used stack size.', 'pxEndOfStack', 'get_ss_val')
SL = ('Free/unused stack size.', 'pxTopOfStack', 'get_sl_val')
SHW = ('Stack high water mark (amount of stack space that has not been touched).', 'pxStack', 'get_shw_val')
RTC = ('Stores the amount of time the task has spent in the Running state.', 'ulRunTimeCounter', 'get_val')

def get_ss_val(self, task):
Expand All @@ -42,6 +43,54 @@ def get_ss_val(self, task):
def get_sl_val(self, task):
return abs(int(task['pxStack']) - int(task['pxTopOfStack']))

def get_shw_val(self, task):
# If neither of these symbols are defined, it's likely that FreeRTOS
# was not configured to initialize stacks with fill bytes, and so there
# is no way to compute the high water mark.
hwm_sym, _ = gdb.lookup_symbol('uxTaskGetStackHighWaterMark')
hwm2_sym, _ = gdb.lookup_symbol('uxTaskGetStackHighWaterMark2')
if hwm_sym is None and hwm2_sym is None:
return '??'

fill_byte = b'\xa5' # tskSTACK_FILL_BYTE

if not any(field.name == 'pxEndOfStack' for field in task.type.fields()):
# pxEndOfStack is not defined. Assume this means the stack grows
# downward (portSTACK_GROWTH == -1). In this case, we can only
# read out the currently unused part of the stack.
stack = gdb.selected_inferior().read_memory(
task['pxStack'],
int(task['pxTopOfStack']) - int(task['pxStack']))
direction = -1
else:
# pxEndOfStack is defined, so we can read out the complete stack.
stack = gdb.selected_inferior().read_memory(
task['pxStack'],
int(task['pxEndOfStack']) - int(task['pxStack']))
# Guess the stack growth direction based on which end appears to be
# unused.
if stack[:8] == fill_byte * 8:
direction = -1
elif stack[-8:] == fill_byte * 8:
direction = 1
else:
return '??' # no fill bytes found so we don't know

count = 0
if direction == 1:
# Stack grows upwards, so start counting untouched bytes from the
# end backwards.
stack = reversed(stack)
for b in stack:
if b == fill_byte:
count += 1
else:
break

# Round down to nearest multiple of sizeof(StackType_t).
word_size = gdb.lookup_type('StackType_t').sizeof
count = count // word_size * word_size
return count

def get_current_tcbs():
current_tcb_arr = []
Expand Down