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| author | Mark Rutland | 2016-01-06 12:05:27 +0100 |
|---|---|---|
| committer | Will Deacon | 2016-01-06 17:00:56 +0100 |
| commit | 2a803c4db615d85126c5c7afd5849a3cfde71422 (patch) | |
| tree | 1d1726389bbdf21247488ecf3b0af3a35edafc00 /arch/arm64 | |
| parent | efi: stub: define DISABLE_BRANCH_PROFILING for all architectures (diff) | |
| download | kernel-qcow2-linux-2a803c4db615d85126c5c7afd5849a3cfde71422.tar.gz kernel-qcow2-linux-2a803c4db615d85126c5c7afd5849a3cfde71422.tar.xz kernel-qcow2-linux-2a803c4db615d85126c5c7afd5849a3cfde71422.zip | |
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.S | 15 |
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) |