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authorDave Hansen <dave.hansen@linux.intel.com>2018-04-06 22:55:13 +0200
committerIngo Molnar <mingo@kernel.org>2018-04-12 09:05:58 +0200
commit430d4005b8b41c19966dd3bfdb33004bdb2de01c (patch)
tree0c24ef41097badc4e85ce4d61d4fe2fd5af7a621 /lib/test_module.c
parentx86/mm: Remove extra filtering in pageattr code (diff)
downloadlinux-430d4005b8b41c19966dd3bfdb33004bdb2de01c.tar.xz
linux-430d4005b8b41c19966dd3bfdb33004bdb2de01c.zip
x86/mm: Comment _PAGE_GLOBAL mystery
I was mystified as to where the _PAGE_GLOBAL in the kernel page tables for kernel text came from. I audited all the places I could find, but I missed one: head_64.S. The page tables that we create in here live for a long time, and they also have _PAGE_GLOBAL set, despite whether the processor supports it or not. It's harmless, and we got *lucky* that the pageattr code accidentally clears it when we wipe it out of __supported_pte_mask and then later try to mark kernel text read-only. Comment some of these properties to make it easier to find and understand in the future. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Kees Cook <keescook@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nadav Amit <namit@vmware.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180406205513.079BB265@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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