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We're only calling that one function on the shadow stack so I doubt it'd result in a real issue, but might as well keep this lined up. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Palmer Dabbelt Reviewed-by: Jisheng Zhang --- arch/riscv/kernel/traps.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index be54ccea8c47..acdfcacd7e57 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -206,7 +206,7 @@ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used * to get per-cpu overflow stack(get_overflow_stack). */ -long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)]; +long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); asmlinkage unsigned long get_overflow_stack(void) { return (unsigned long)this_cpu_ptr(overflow_stack) + From patchwork Wed Nov 30 02:35:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Palmer Dabbelt X-Patchwork-Id: 13059405 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C30E4C4167B for ; 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Tue, 29 Nov 2022 18:35:46 -0800 (PST) Subject: [PATCH 2/2] RISC-V: Add some comments about the shadow and overflow stacks Date: Tue, 29 Nov 2022 18:35:15 -0800 Message-Id: <20221130023515.20217-2-palmer@rivosinc.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221130023515.20217-1-palmer@rivosinc.com> References: <20221130023515.20217-1-palmer@rivosinc.com> MIME-Version: 1.0 Cc: Palmer Dabbelt From: Palmer Dabbelt To: jszhang@kernel.org, guoren@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221129_183548_434291_F2C174DA X-CRM114-Status: GOOD ( 12.53 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org It took me a while to page all this back in when trying to review the recent spin_shadow_stack, so I figured I'd just write up some comments. Signed-off-by: Palmer Dabbelt Reviewed-by: Guo Ren Reviewed-by: Jisheng Zhang --- arch/riscv/kernel/traps.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index acdfcacd7e57..336d4aadadb1 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -200,18 +200,18 @@ void __init trap_init(void) } #ifdef CONFIG_VMAP_STACK +/* + * Extra stack space that allows us to provide panic messages when the kernel + * has overflowed its stack. + */ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)__aligned(16); /* - * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used - * to get per-cpu overflow stack(get_overflow_stack). + * A temporary stack for use by handle_kernel_stack_overflow. This is used so + * we can call into C code to get the per-hart overflow stack. Usage of this + * stack must be protected by spin_shadow_stack. */ long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); -asmlinkage unsigned long get_overflow_stack(void) -{ - return (unsigned long)this_cpu_ptr(overflow_stack) + - OVERFLOW_STACK_SIZE; -} /* * A pseudo spinlock to protect the shadow stack from being used by multiple @@ -222,6 +222,12 @@ asmlinkage unsigned long get_overflow_stack(void) */ unsigned long spin_shadow_stack; +asmlinkage unsigned long get_overflow_stack(void) +{ + return (unsigned long)this_cpu_ptr(overflow_stack) + + OVERFLOW_STACK_SIZE; +} + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk = (unsigned long)current->stack;