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Date: Mon, 27 Dec 2021 17:06:04 -0800 From: Dan Li <ashimida@...ux.alibaba.com> To: catalin.marinas@....com, will@...nel.org, mark.rutland@....com, samitolvanen@...gle.com, maz@...nel.org, joey.gouly@....com, pcc@...gle.com Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, Dan Li <ashimida@...ux.alibaba.com> Subject: [PATCH] [RFC] aarch64: scs: reload shadow call stack in user exception entry When el0 exception occurs, kernel_entry/exit will load/save tsk->scs_sp to ensure scs working properly. AFAIK, the SCS offset should always be 0 at this time. Is it reasonable to reload x18 to scs_base directly in kernel_entry here, or am I missing something? Signed-off-by: Dan Li <ashimida@...ux.alibaba.com> --- arch/arm64/include/asm/scs.h | 7 +++++++ arch/arm64/kernel/entry.S | 3 +-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h index 8297bccf0784..2bc0d0575e75 100644 --- a/arch/arm64/include/asm/scs.h +++ b/arch/arm64/include/asm/scs.h @@ -9,6 +9,10 @@ #ifdef CONFIG_SHADOW_CALL_STACK scs_sp .req x18 + .macro scs_reload tsk + ldr scs_sp, [\tsk, #TSK_TI_SCS_BASE] + .endm + .macro scs_load tsk ldr scs_sp, [\tsk, #TSK_TI_SCS_SP] .endm @@ -17,6 +21,9 @@ str scs_sp, [\tsk, #TSK_TI_SCS_SP] .endm #else + .macro scs_reload tsk + .endm + .macro scs_load tsk .endm diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index bc6d5a970a13..57547a3e4f7c 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -265,7 +265,7 @@ alternative_if ARM64_HAS_ADDRESS_AUTH alternative_else_nop_endif 1: - scs_load tsk + scs_reload tsk .else add x21, sp, #PT_REGS_SIZE get_current_task tsk @@ -365,7 +365,6 @@ alternative_if ARM64_WORKAROUND_845719 alternative_else_nop_endif #endif 3: - scs_save tsk /* Ignore asynchronous tag check faults in the uaccess routines */ ldr x0, [tsk, THREAD_SCTLR_USER] -- 2.17.1
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