From nobody Sun May 10 08:26:37 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FDD2C433EF for ; Sun, 15 May 2022 05:13:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235577AbiEOFMN (ORCPT ); Sun, 15 May 2022 01:12:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234060AbiEOFML (ORCPT ); Sun, 15 May 2022 01:12:11 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20DE413F9A for ; Sat, 14 May 2022 22:12:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id AACA2B80AF5 for ; Sun, 15 May 2022 05:12:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C031EC385B8; Sun, 15 May 2022 05:12:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652591527; bh=7qrCaB40KpTA4LFePIZNR7GNlq1nhQHQleoNK2FIHSs=; h=From:To:Cc:Subject:Date:From; b=WsrdjM7cRFsGywpXdiSL3UiQtSKiF3Jj42RyLkwUD7+xomyVlUsgUQ6WRDTvcr5wZ CiIVsIswGZWpxw9kufLDPu1TclvR9w/ww1bvLYpiLzwEhRISL2lTr6kvwqygbtvUPL bRfJ+6+oyCmPeW3llVDXjVCJymGVQ+jbROfYkbgv3QUXhm1aXZGPBm/eMR0K4aq7Yq 0aOcYhXAKOdwa7YogjP6UfOgne/+l2IaxfmN/3zFfnN9qQlPTcyMw52DTTD5G76WLC CKEJaZiTuxKRVrgoikZ1boKoOwQWvUshA2A5hBwx9IY68PWXeFOFHsPNsyfm1ltVTt IF20ByfTxb4fg== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] riscv: add irq stack support Date: Sun, 15 May 2022 13:03:36 +0800 Message-Id: <20220515050336.1023-1-jszhang@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Currently, IRQs are still handled on the kernel stack of the current task on riscv platforms. If the task has a deep call stack at the time of interrupt, and handling the interrupt also requires a deep stack, it's possible to see stack overflow. Before this patch, the stack_max_size of a v5.17-rc1 kernel running on a lichee RV board gave: ~ # cat /sys/kernel/debug/tracing/stack_max_size 3736 After this patch, ~ # cat /sys/kernel/debug/tracing/stack_max_size 3176 We reduce the max kernel stack usage by 560 bytes! Signed-off-by: Jisheng Zhang --- since v2: - rebase on v5.18-rcN - update commit msg, I.E remove the "it's possible to reduce the THREAD_SIZE to 8KB for RV64 platforms..." since v1: - add __ro_after_init to the irq_stack[] array. arch/riscv/include/asm/thread_info.h | 1 + arch/riscv/kernel/asm-offsets.c | 2 ++ arch/riscv/kernel/entry.S | 33 +++++++++++++++++++++++++--- arch/riscv/kernel/irq.c | 16 ++++++++++++++ 4 files changed, 49 insertions(+), 3 deletions(-) diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/= thread_info.h index 74d888c8d631..98ea73721a0b 100644 --- a/arch/riscv/include/asm/thread_info.h +++ b/arch/riscv/include/asm/thread_info.h @@ -25,6 +25,7 @@ #endif #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) =20 +#define IRQ_STACK_SIZE THREAD_SIZE /* * By aligning VMAP'd stacks to 2 * THREAD_SIZE, we can detect overflow by * checking sp & (1 << THREAD_SHIFT), which we can do cheaply in the entry diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offset= s.c index df9444397908..9e32748af0e8 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -37,6 +37,8 @@ void asm_offsets(void) OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); + OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu); + OFFSET(TASK_STACK, task_struct, stack); =20 OFFSET(TASK_THREAD_F0, task_struct, thread.fstate.f[0]); OFFSET(TASK_THREAD_F1, task_struct, thread.fstate.f[1]); diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index c8b9ce274b9a..e91cae183ef4 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -126,12 +126,39 @@ skip_context_tracking: */ bge s4, zero, 1f =20 - la ra, ret_from_exception + /* preserve the sp */ + move s0, sp =20 - /* Handle interrupts */ move a0, sp /* pt_regs */ + + /* + * Compare sp with the base of the task stack. + * If the top ~(THREAD_SIZE - 1) bits match, we are on a task stack, + * and should switch to the irq stack. + */ + REG_L t0, TASK_STACK(tp) + xor t0, t0, s0 + li t1, ~(THREAD_SIZE - 1) + and t0, t0, t1 + bnez t0, 2f + + la t1, irq_stack + REG_L t2, TASK_TI_CPU(tp) + slli t2, t2, RISCV_LGPTR + add t1, t1, t2 + REG_L t2, 0(t1) + li t1, IRQ_STACK_SIZE + /* switch to the irq stack */ + add sp, t2, t1 + +2: + /* Handle interrupts */ la a1, generic_handle_arch_irq - jr a1 + jalr a1 + + /* Restore sp */ + move sp, s0 + j ret_from_exception 1: /* * Exceptions run with interrupts enabled or disabled depending on the diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c index 7207fa08d78f..f20cbfd42e82 100644 --- a/arch/riscv/kernel/irq.c +++ b/arch/riscv/kernel/irq.c @@ -10,6 +10,8 @@ #include #include =20 +void *irq_stack[NR_CPUS] __ro_after_init; + int arch_show_interrupts(struct seq_file *p, int prec) { show_ipi_stats(p, prec); @@ -18,7 +20,21 @@ int arch_show_interrupts(struct seq_file *p, int prec) =20 void __init init_IRQ(void) { + int cpu; + irqchip_init(); if (!handle_arch_irq) panic("No interrupt controller found."); + + for_each_possible_cpu(cpu) { +#ifdef CONFIG_VMAP_STACK + void *s =3D __vmalloc_node(IRQ_STACK_SIZE, THREAD_ALIGN, + THREADINFO_GFP, cpu_to_node(cpu), + __builtin_return_address(0)); +#else + void *s =3D (void *)__get_free_pages(GFP_KERNEL, get_order(IRQ_STACK_SIZ= E)); +#endif + + irq_stack[cpu] =3D s; + } } --=20 2.34.1