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arm64: fix KASLR boot-time I-cache maintenance 

Commit f80fb3a3d5 ("arm64: add support for kernel ASLR") missed a
DSB necessary to complete I-cache maintenance in the primary boot path,
and hence stale instructions may still be present in the I-cache and may
be executed until the I-cache maintenance naturally completes.

Since commit 8ec4198743 ("arm64: mm: ensure patched kernel text is
fetched from PoU"), all CPUs invalidate their I-caches after their MMU
is enabled. Prior a CPU's MMU having been enabled, arbitrary lines may
have been fetched from the PoC into I-caches. We never patch text
expected to be executed with the MMU off. Thus, it is unnecessary to
perform broadcast I-cache maintenance in the primary boot path.

This patch reduces the scope of the I-cache maintenance to the local
CPU, and adds the missing DSB with similar scope, matching prior
maintenance in the primary boot path.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Ard Biesehvuel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2016-03-15 11:22:57 +00:00 committed by Catalin Marinas
parent b660950c60
commit b90b4a608e
1 changed files with 3 additions and 2 deletions
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5
arch/arm64/kernel/head.S
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@ -766,8 +766,9 @@ __enable_mmu:
msr sctlr_el1, x19 // re-enable the MMU
isb
ic ialluis // flush instructions fetched
isb // via old mapping
ic iallu // flush instructions fetched
dsb nsh // via old mapping
isb
add x27, x27, x23 // relocated __mmap_switched
#endif
br x27