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    SubjectRe: [PATCH 26/26] x86, pkeys: Documentation
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    On 10/01/2015 06:38 PM, Linus Torvalds wrote:
    > On Thu, Oct 1, 2015 at 6:56 PM, Dave Hansen <dave@sr71.net> wrote:
    >>
    >> Also, a quick ftrace showed that most mmap() callers that set PROT_EXEC
    >> also set PROT_READ. I'm just assuming that folks are setting PROT_READ
    >> but aren't _really_ going to read it, so we can safely deny them all
    >> access other than exec.
    >
    > That's a completely insane assumption. There are tons of reasons to
    > have code and read-only data in the same segment, and it's very
    > traditional. Just assuming that you only execute out of something that
    > has PROT_EXEC | PROT_READ is insane.

    Yes, it's insane, and I confirmed that ld.so actually reads some stuff
    out of the first page of the r-x part of the executable.

    But, it did find a bug in my code where I wouldn't allow instruction
    fetches to fault in pages in a pkey-protected area, so it wasn't a
    completely worthless exercise.


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