From b90b4a608ea2401cc491828f7a385edd2e236e37 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 15 Mar 2016 11:22:57 +0000 Subject: [PATCH] arm64: fix KASLR boot-time I-cache maintenance Commit f80fb3a3d50843a4 ("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 8ec41987436d566f ("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 Acked-by: Ard Biesehvuel Cc: Will Deacon Signed-off-by: Catalin Marinas --- arch/arm64/kernel/head.S | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 50c2134a4aaf..1672ca9e963b 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -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 -- 2.20.1