From 276e93279a630657fff4b086ba14c95955912dfa Mon Sep 17 00:00:00 2001 From: Kristina Martsenko Date: Wed, 3 May 2017 16:37:47 +0100 Subject: [PATCH] arm64: entry: improve data abort handling of tagged pointers When handling a data abort from EL0, we currently zero the top byte of the faulting address, as we assume the address is a TTBR0 address, which may contain a non-zero address tag. However, the address may be a TTBR1 address, in which case we should not zero the top byte. This patch fixes that. The effect is that the full TTBR1 address is passed to the task's signal handler (or printed out in the kernel log). When handling a data abort from EL1, we leave the faulting address intact, as we assume it's either a TTBR1 address or a TTBR0 address with tag 0x00. This is true as far as I'm aware, we don't seem to access a tagged TTBR0 address anywhere in the kernel. Regardless, it's easy to forget about address tags, and code added in the future may not always remember to remove tags from addresses before accessing them. So add tag handling to the EL1 data abort handler as well. This also makes it consistent with the EL0 data abort handler. Fixes: d50240a5f6ce ("arm64: mm: permit use of tagged pointers at EL0") Cc: # 3.12.x- Reviewed-by: Dave Martin Acked-by: Will Deacon Signed-off-by: Kristina Martsenko Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/asm-uaccess.h | 9 +++++++++ arch/arm64/kernel/entry.S | 5 +++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h index df411f3..ecd9788 100644 --- a/arch/arm64/include/asm/asm-uaccess.h +++ b/arch/arm64/include/asm/asm-uaccess.h @@ -62,4 +62,13 @@ alternative_if ARM64_ALT_PAN_NOT_UAO alternative_else_nop_endif .endm +/* + * Remove the address tag from a virtual address, if present. + */ + .macro clear_address_tag, dst, addr + tst \addr, #(1 << 55) + bic \dst, \addr, #(0xff << 56) + csel \dst, \dst, \addr, eq + .endm + #endif diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 43512d4..b738880 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -428,12 +428,13 @@ el1_da: /* * Data abort handling */ - mrs x0, far_el1 + mrs x3, far_el1 enable_dbg // re-enable interrupts if they were enabled in the aborted context tbnz x23, #7, 1f // PSR_I_BIT enable_irq 1: + clear_address_tag x0, x3 mov x2, sp // struct pt_regs bl do_mem_abort @@ -594,7 +595,7 @@ el0_da: // enable interrupts before calling the main handler enable_dbg_and_irq ct_user_exit - bic x0, x26, #(0xff << 56) + clear_address_tag x0, x26 mov x1, x25 mov x2, sp bl do_mem_abort -- 2.7.4