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x86/mm/32: Set NX in __supported_pte_mask before enabling paging

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There's a short window in which very early mappings can end up
with NX clear because they are created before we've noticed that
we have NX.

It turns out that we detect NX very early, so there's no need to
defer __supported_pte_mask setup.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2b544627345f7110160545a3f47031eb45c3ad4f.1453239349.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-01-19 13:38:58 -08:00 committed by Ingo Molnar
parent 43c75f933b
commit 320d25b6a0
2 changed files with 8 additions and 3 deletions
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6
arch/x86/kernel/head_32.S
View file

@ -389,6 +389,12 @@ default_entry:
/* Make changes effective */
wrmsr
/*
* And make sure that all the mappings we set up have NX set from
* the beginning.
*/
orl $(1 << (_PAGE_BIT_NX - 32)), pa(__supported_pte_mask + 4)
enable_paging:
/*

5
arch/x86/mm/setup_nx.c
View file

@ -31,9 +31,8 @@ early_param("noexec", noexec_setup);
void x86_configure_nx(void)
{
if (boot_cpu_has(X86_FEATURE_NX) && !disable_nx)
__supported_pte_mask |= _PAGE_NX;
else
/* If disable_nx is set, clear NX on all new mappings going forward. */
if (disable_nx)
__supported_pte_mask &= ~_PAGE_NX;
}