Messages in this thread | | | Date | Tue, 20 Feb 2018 15:30:09 -0800 | From | "Luck, Tony" <> | Subject | Re: [PATCH 1/2] fs/efivarfs: restrict inode permissions |
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On Tue, Feb 20, 2018 at 02:01:51PM -0800, Linus Torvalds wrote: > And just on general principlies, I don't want to see weasel-wordy > commit messages like > > "Reading certain EFI variables trigger SMIs" > > I understand *writing* them causing SMI's due to some flash protection > scheme. What's the reading thing? And why aren't we calling that > garbage out?
Too much weasel there. Should say:
EFI[1] stinks. Reading any file in /sys/firmware/efi/efivars/ generates 4 (yes FOUR!) SMIs.
# rdmsr 0x34 14e2 # cat /sys/firmware/efi/efivars/ConIn-8be4df61-93ca-11d2-aa0d-00e098032b8c > /dev/null # rdmsr 0x34 14e6
-Tony
[1] I didn't dig through the Linux code to check whether we manage to get those four SMIs from a single EFI call, or whether we make multiple EFI calls to open/read/close one file. It is possible that we stink a bit too if we are doing more EFI calls than required.
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