diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2016-01-06 11:05:27 +0000 |
|---|---|---|
| committer | Jeff Vander Stoep <jeffv@google.com> | 2016-09-18 14:40:40 -0700 |
| commit | a725004a74ab543510a8158b206c334756e9d8cf (patch) | |
| tree | 119310ae92e2b6cefed5485aba371512ed30cdca /arch/arm64 | |
| parent | 3c31c6d7098894f0bf886ebe711fd930855626e5 (diff) | |
UPSTREAM: 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>
Bug: 30369029
Patchset: rework-pagetable
(cherry picked from commit 2a803c4db615d85126c5c7afd5849a3cfde71422)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: I3dc7050fe5566f2126cbea9abfa6063c8e6b029a
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/kernel/head.S | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 17ce7285bb12..917d98108b3f 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) |