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Use the 'force' flag for bss zeroing (#719)

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* Clean up bss trailer zeroing
This commit is contained in:
Yan Ivnitskiy
2018-01-31 11:47:46 -05:00
committed by GitHub
parent a1f809732d
commit 9f7b87d0b8
1 changed files with 11 additions and 34 deletions
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manticore/platforms/linux.py
+11 -34
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@@ -839,31 +839,13 @@ class Linux(Platform):
entry = elf_entry
real_elf_brk = elf_brk
# We need to explicitly zero any fractional pages
# after the data section (i.e. bss). This would
# contain the junk from the file that should not
# be in memory
#TODO:
#cpu.write_bytes(elf_bss, '\x00'*((elf_bss | (align-1))-elf_bss))
logger.debug("Zeroing main elf fractional pages. From %x to %x.", elf_bss, elf_brk)
logger.debug("Main elf bss:%x",elf_bss)
logger.debug("Main elf brk %x:",elf_brk)
#FIXME Need a way to inspect maps and perms so
#we can rollback all to the initial state after zeroing
#if elf_brk-elf_bss > 0:
# saved_perms = cpu.mem.perms(elf_bss)
# cpu.memory.mprotect(cpu.mem._ceil(elf_bss), elf_brk-elf_bss, 'rw ')
# logger.debug("Zeroing main elf fractional pages (%d bytes)", elf_brk-elf_bss)
# cpu.write_bytes(elf_bss, ['\x00'] * (elf_brk-elf_bss))
# cpu.memory.mprotect(cpu.memory._ceil(elf_bss), elf_brk-elf_bss, saved_perms)
if cpu.memory.access_ok(slice(elf_bss, elf_brk), 'w'):
cpu.memory[elf_bss:elf_brk] = '\x00'*(elf_brk-elf_bss)
else:
logger.warning("Failing to zerify the trailing: elf_brk-elf_bss")
# We need to explicitly clear bss, as fractional pages will have data from the file
bytes_to_clear = elf_brk - elf_bss
if bytes_to_clear > 0:
logger.debug("Zeroing main elf fractional pages. From bss(%x) to brk(%x), %d bytes.",
elf_bss, elf_brk, bytes_to_clear)
cpu.write_bytes(elf_bss, '\x00' * bytes_to_clear, force=True)
stack_size = 0x21000
@@ -932,16 +914,11 @@ class Linux(Platform):
entry += base
interpreter_base = base
logger.debug("Zeroing interpreter elf fractional pages. From %x to %x.", elf_bss, elf_brk)
logger.debug("Interpreter bss:%x", elf_bss)
logger.debug("Interpreter brk %x:", elf_brk)
cpu.memory.mprotect(cpu.memory._floor(elf_bss), elf_brk-elf_bss, 'rw ')
try:
cpu.memory[elf_bss:elf_brk] = '\x00'*(elf_brk-elf_bss)
except Exception, e:
logger.debug("Exception zeroing Interpreter fractional pages: %s",str(e))
#TODO #FIXME mprotect as it was before zeroing?
bytes_to_clear = elf_brk - elf_bss
if bytes_to_clear > 0:
logger.debug("Zeroing interpreter elf fractional pages. From bss(%x) to brk(%x), %d bytes.",
elf_bss, elf_brk, bytes_to_clear)
cpu.write_bytes(elf_bss, '\x00' * bytes_to_clear, force=True)
#free reserved brk space