LinuxHelper: open the device with buffering=0 to avoid caching #2058
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…eading physical memory
npmitche
approved these changes
Feb 6, 2024
npmitche
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Sae86,
ErikBjorge,
frinzell,
BrentHoltsclaw,
dscott90 and
jun2zhou
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| @@ -188,7 +188,8 @@ | |||
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| estr = "Unable to open chipsec device. Did you run as root/sudo and load the driver?\n {}" | |||
| try: | |||
| self.dev_fh = open(self.DEVICE_NAME, "rb+") | |||
| # Do not buffer access to physical memory... | |||
| self.dev_fh = open(self.DEVICE_NAME, "rb+", buffering=0) | |||
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dscott90
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Feb 7, 2024
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LinuxHelper: open the device with buffering=0 to avoid caching when reading physical memory
I am using chipsec to read and write physical memory, and particularly expect this memory to change because some devices use it for DMA.
On linux, the python helper linuxhelper.py opens the device "/dev/chipsec" without setting
buffering=0. It implies that calling theread_physical_memAPI will be cached ifflush()is not called.flush()is only called when writing. So if I expect a change in the DMA, it will never occur until I usewrite_physical_mem.I think the read/write accesses to the device and therefore to physical memory should never be cached by the python bindings.
It might have some performance impact on the tool, but I don't think this is the behavior expected.