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#!/usr/bin/env python3
# sem_slots.py - read or write the per-channel u32 completion counters of a
# guest process (verification and fallback for the host's counter publish).
#
# Usage:
# sudo python3 sem_slots.py <pid> <first-va> [count] # read
# sudo python3 sem_slots.py <pid> <first-va> [count] --write <v> # write
#
# The slots are 16 bytes apart (one u32 per channel). Reading needs pagemap/
# mem access as root; writing uses /proc/<pid>/mem and mirrors the gdb poke
# used in earlier sessions (e.g. --write 1 to arm every waiter).
import os
import sys
def main():
if len(sys.argv) < 3:
print(__doc__)
return 1
pid = int(sys.argv[1])
first = int(sys.argv[2], 16)
count = 20
write_val = None
i = 3
while i < len(sys.argv):
if sys.argv[i] == '--write':
write_val = int(sys.argv[i + 1], 0)
i += 2
continue
count = int(sys.argv[i], 0)
i += 1
flags = os.O_RDWR if write_val is not None else os.O_RDONLY
mem = os.open('/proc/%d/mem' % pid, flags)
try:
for n in range(count):
va = first + n * 16
if write_val is not None:
os.pwrite(mem, write_val.to_bytes(4, 'little'), va)
print('idx=%d VA=0x%x written=%u' % (n, va, write_val))
else:
v = int.from_bytes(os.pread(mem, 4, va), 'little')
print('idx=%d VA=0x%x val=%u' % (n, va, v))
finally:
os.close(mem)
return 0
if __name__ == '__main__':
sys.exit(main())
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