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authorMark Rutland <mark.rutland@arm.com>2016-01-06 11:05:27 +0000
committerWill Deacon <will.deacon@arm.com>2016-01-06 16:00:56 +0000
commit2a803c4db615d85126c5c7afd5849a3cfde71422 (patch)
tree1d1726389bbdf21247488ecf3b0af3a35edafc00 /arch/arm64
parentb523e185bba36164ca48a190f5468c140d815414 (diff)
downloadlinux-2a803c4db615d85126c5c7afd5849a3cfde71422.tar.bz2
arm64: head.S: use memset to clear BSS
Currently we use an open-coded memzero to clear the BSS. As it is a trivial implementation, it is sub-optimal. Our optimised memset doesn't use the stack, is position-independent, and for the memzero case can use of DC ZVA to clear large blocks efficiently. In __mmap_switched the MMU is on and there are no live caller-saved registers, so we can safely call an uninstrumented memset. This patch changes __mmap_switched to use memset when clearing the BSS. We use the __pi_memset alias so as to avoid any instrumentation in all kernel configurations. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/head.S15
1 files changed, 7 insertions, 8 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b363f340f2c7..ffe9c2b6431b 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -415,14 +415,13 @@ ENDPROC(__create_page_tables)
*/
.set initial_sp, init_thread_union + THREAD_START_SP
__mmap_switched:
- adr_l x6, __bss_start
- adr_l x7, __bss_stop
-
-1: cmp x6, x7
- b.hs 2f
- str xzr, [x6], #8 // Clear BSS
- b 1b
-2:
+ // Clear BSS
+ adr_l x0, __bss_start
+ mov x1, xzr
+ adr_l x2, __bss_stop
+ sub x2, x2, x0
+ bl __pi_memset
+
adr_l sp, initial_sp, x4
mov x4, sp
and x4, x4, #~(THREAD_SIZE - 1)