add ostep homeworks
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yuchen
192
related_info/ostep/ostep4-paging-linear-translate.py
Executable file
192
related_info/ostep/ostep4-paging-linear-translate.py
Executable file
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#! /usr/bin/env python
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import sys
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from optparse import OptionParser
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import random
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import math
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def mustbepowerof2(bits, size, msg):
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if math.pow(2,bits) != size:
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print 'Error in argument: %s' % msg
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sys.exit(1)
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def mustbemultipleof(bignum, num, msg):
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if (int(float(bignum)/float(num)) != (int(bignum) / int(num))):
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print 'Error in argument: %s' % msg
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sys.exit(1)
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def convert(size):
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length = len(size)
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lastchar = size[length-1]
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if (lastchar == 'k') or (lastchar == 'K'):
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m = 1024
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nsize = int(size[0:length-1]) * m
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elif (lastchar == 'm') or (lastchar == 'M'):
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m = 1024*1024
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nsize = int(size[0:length-1]) * m
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elif (lastchar == 'g') or (lastchar == 'G'):
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m = 1024*1024*1024
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nsize = int(size[0:length-1]) * m
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else:
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nsize = int(size)
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return nsize
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#
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# main program
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#
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parser = OptionParser()
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parser.add_option('-A', '--addresses', default='-1',
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help='a set of comma-separated pages to access; -1 means randomly generate',
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action='store', type='string', dest='addresses')
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parser.add_option('-s', '--seed', default=0, help='the random seed', action='store', type='int', dest='seed')
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parser.add_option('-a', '--asize', default='16k', help='address space size (e.g., 16, 64k, 32m, 1g)', action='store', type='string', dest='asize')
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parser.add_option('-p', '--physmem', default='64k', help='physical memory size (e.g., 16, 64k, 32m, 1g)', action='store', type='string', dest='psize')
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parser.add_option('-P', '--pagesize', default='4k', help='page size (e.g., 4k, 8k, whatever)', action='store', type='string', dest='pagesize')
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parser.add_option('-n', '--numaddrs', default=5, help='number of virtual addresses to generate', action='store', type='int', dest='num')
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parser.add_option('-u', '--used', default=50, help='percent of virtual address space that is used', action='store', type='int', dest='used')
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parser.add_option('-v', help='verbose mode', action='store_true', default=False, dest='verbose')
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parser.add_option('-c', help='compute answers for me', action='store_true', default=False, dest='solve')
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(options, args) = parser.parse_args()
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print 'ARG seed', options.seed
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print 'ARG address space size', options.asize
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print 'ARG phys mem size', options.psize
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print 'ARG page size', options.pagesize
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print 'ARG verbose', options.verbose
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print 'ARG addresses', options.addresses
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print ''
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random.seed(options.seed)
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asize = convert(options.asize)
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psize = convert(options.psize)
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pagesize = convert(options.pagesize)
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addresses = str(options.addresses)
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if psize <= 1:
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print 'Error: must specify a non-zero physical memory size.'
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exit(1)
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if asize < 1:
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print 'Error: must specify a non-zero address-space size.'
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exit(1)
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if psize <= asize:
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print 'Error: physical memory size must be GREATER than address space size (for this simulation)'
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exit(1)
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if psize >= convert('1g') or asize >= convert('1g'):
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print 'Error: must use smaller sizes (less than 1 GB) for this simulation.'
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exit(1)
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mustbemultipleof(asize, pagesize, 'address space must be a multiple of the pagesize')
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mustbemultipleof(psize, pagesize, 'physical memory must be a multiple of the pagesize')
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# print some useful info, like the darn page table
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pages = psize / pagesize;
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import array
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used = array.array('i')
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pt = array.array('i')
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for i in range(0,pages):
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used.insert(i,0)
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vpages = asize / pagesize
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# now, assign some pages of the VA
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vabits = int(math.log(float(asize))/math.log(2.0))
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mustbepowerof2(vabits, asize, 'address space must be a power of 2')
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pagebits = int(math.log(float(pagesize))/math.log(2.0))
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mustbepowerof2(pagebits, pagesize, 'page size must be a power of 2')
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vpnbits = vabits - pagebits
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pagemask = (1 << pagebits) - 1
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# import ctypes
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# vpnmask = ctypes.c_uint32(~pagemask).value
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vpnmask = 0xFFFFFFFF & ~pagemask
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#if vpnmask2 != vpnmask:
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# print 'ERROR'
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# exit(1)
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# print 'va:%d page:%d vpn:%d -- %08x %08x' % (vabits, pagebits, vpnbits, vpnmask, pagemask)
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print ''
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print 'The format of the page table is simple:'
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print 'The high-order (left-most) bit is the VALID bit.'
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print ' If the bit is 1, the rest of the entry is the PFN.'
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print ' If the bit is 0, the page is not valid.'
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print 'Use verbose mode (-v) if you want to print the VPN # by'
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print 'each entry of the page table.'
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print ''
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print 'Page Table (from entry 0 down to the max size)'
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for v in range(0,vpages):
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done = 0
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while done == 0:
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if ((random.random() * 100.0) > (100.0 - float(options.used))):
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u = int(pages * random.random())
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if used[u] == 0:
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done = 1
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# print '%8d - %d' % (v, u)
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if options.verbose == True:
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print ' [%8d] ' % v,
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else:
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print ' ',
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print '0x%08x' % (0x80000000 | u)
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pt.insert(v,u)
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else:
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# print '%8d - not valid' % v
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if options.verbose == True:
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print ' [%8d] ' % v,
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else:
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print ' ',
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print '0x%08x' % 0
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pt.insert(v,-1)
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done = 1
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print ''
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#
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# now, need to generate virtual address trace
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#
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addrList = []
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if addresses == '-1':
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# need to generate addresses
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for i in range(0, options.num):
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n = int(asize * random.random())
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addrList.append(n)
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else:
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addrList = addresses.split(',')
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print 'Virtual Address Trace'
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for vStr in addrList:
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# vaddr = int(asize * random.random())
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vaddr = int(vStr)
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if options.solve == False:
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print ' VA 0x%08x (decimal: %8d) --> PA or invalid address?' % (vaddr, vaddr)
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else:
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paddr = 0
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# split vaddr into VPN | offset
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vpn = (vaddr & vpnmask) >> pagebits
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if pt[vpn] < 0:
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print ' VA 0x%08x (decimal: %8d) --> Invalid (VPN %d not valid)' % (vaddr, vaddr, vpn)
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else:
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pfn = pt[vpn]
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offset = vaddr & pagemask
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paddr = (pfn << pagebits) | offset
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print ' VA 0x%08x (decimal: %8d) --> %08x (decimal %8d) [VPN %d]' % (vaddr, vaddr, paddr, paddr, vpn)
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print ''
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if options.solve == False:
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print 'For each virtual address, write down the physical address it translates to'
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print 'OR write down that it is an out-of-bounds address (e.g., segfault).'
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print ''
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