From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ard Biesheuvel Date: Mon, 14 Aug 2017 13:53:46 +0100 Message-Id: <20170814125411.22604-6-ard.biesheuvel@linaro.org> In-Reply-To: <20170814125411.22604-1-ard.biesheuvel@linaro.org> References: <20170814125411.22604-1-ard.biesheuvel@linaro.org> Subject: [kernel-hardening] [PATCH 05/30] ARM: head.S: use PC-relative insn sequence for secondary_data To: kernel-hardening@lists.openwall.com Cc: linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Arnd Bergmann , Nicolas Pitre , Russell King , Kees Cook , Thomas Garnier , Marc Zyngier , Mark Rutland , Tony Lindgren , Matt Fleming , Dave Martin List-ID: Replace the open coded PC relative offset calculations with adr_l and ldr_l invocations. This ensures these quantities are invariant under runtime relocation. Cc: Russell King Signed-off-by: Ard Biesheuvel --- arch/arm/kernel/head.S | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index 0a98aec0e39d..6e9df3663a57 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -386,10 +386,8 @@ ENTRY(secondary_startup) /* * Use the page tables supplied from __cpu_up. */ - adr r4, __secondary_data - ldmia r4, {r5, r7, r12} @ address to jump to after - sub lr, r4, r5 @ mmu has been enabled - add r3, r7, lr + adr_l r3, secondary_data + mov_l r12, __secondary_switched ldrd r4, [r3, #0] @ get secondary_data.pgdir ARM_BE8(eor r4, r4, r5) @ Swap r5 and r4 in BE: ARM_BE8(eor r5, r4, r5) @ it can be done in 3 steps @@ -404,22 +402,13 @@ ARM_BE8(eor r4, r4, r5) @ without using a temp reg. ENDPROC(secondary_startup) ENDPROC(secondary_startup_arm) - /* - * r6 = &secondary_data - */ ENTRY(__secondary_switched) - ldr sp, [r7, #12] @ get secondary_data.stack + ldr_l r7, secondary_data + 12 @ get secondary_data.stack + mov sp, r7 mov fp, #0 b secondary_start_kernel ENDPROC(__secondary_switched) - .align - - .type __secondary_data, %object -__secondary_data: - .long . - .long secondary_data - .long __secondary_switched #endif /* defined(CONFIG_SMP) */ -- 2.11.0