From mboxrd@z Thu Jan 1 00:00:00 1970 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 8C9C8C7618B for ; Wed, 15 Mar 2023 12:24:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232289AbjCOMYZ (ORCPT ); Wed, 15 Mar 2023 08:24:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232064AbjCOMYG (ORCPT ); Wed, 15 Mar 2023 08:24:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C72296C03 for ; Wed, 15 Mar 2023 05:22:51 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 492F161D54 for ; Wed, 15 Mar 2023 12:22:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C927C433EF; Wed, 15 Mar 2023 12:22:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678882927; bh=QJSOPGkwVF0wW/Y1ZzPHP2XsMg3TTkuq4bsBm5nEq2M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hBu4mIE6Co3WyUAxFQJgJ9xYO4aghfJT/QX9F9HNpjJLtDUofFEPI96Dvy1A32W7y l7aNNlP37bfVSoTcBkMPJJIuTMYcgNL2Jqo7xQa8Puk0U9/aRlcRn+CqMpjZ7+le/C ZbAy7C9Yk0AJi5IaLYjACX6+bOncM9ZmEO9iUXz8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Steven Rostedt , Changbin Du , Palmer Dabbelt , Conor Dooley , Palmer Dabbelt , Sasha Levin Subject: [PATCH 5.10 055/104] RISC-V: Dont check text_mutex during stop_machine Date: Wed, 15 Mar 2023 13:12:26 +0100 Message-Id: <20230315115734.284840356@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230315115731.942692602@linuxfoundation.org> References: <20230315115731.942692602@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Conor Dooley [ Upstream commit 2a8db5ec4a28a0fce822d10224db9471a44b6925 ] We're currently using stop_machine() to update ftrace & kprobes, which means that the thread that takes text_mutex during may not be the same as the thread that eventually patches the code. This isn't actually a race because the lock is still held (preventing any other concurrent accesses) and there is only one thread running during stop_machine(), but it does trigger a lockdep failure. This patch just elides the lockdep check during stop_machine. Fixes: c15ac4fd60d5 ("riscv/ftrace: Add dynamic function tracer support") Suggested-by: Steven Rostedt Reported-by: Changbin Du Signed-off-by: Palmer Dabbelt Signed-off-by: Conor Dooley Link: https://lore.kernel.org/r/20230303143754.4005217-1-conor.dooley@microchip.com Signed-off-by: Palmer Dabbelt Signed-off-by: Sasha Levin --- arch/riscv/include/asm/ftrace.h | 2 +- arch/riscv/include/asm/patch.h | 2 ++ arch/riscv/kernel/ftrace.c | 14 ++++++++++++-- arch/riscv/kernel/patch.c | 28 +++++++++++++++++++++++++--- 4 files changed, 40 insertions(+), 6 deletions(-) --- a/arch/riscv/include/asm/ftrace.h +++ b/arch/riscv/include/asm/ftrace.h @@ -83,6 +83,6 @@ int ftrace_init_nop(struct module *mod, #define ftrace_init_nop ftrace_init_nop #endif -#endif +#endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* _ASM_RISCV_FTRACE_H */ --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -9,4 +9,6 @@ int patch_text_nosync(void *addr, const void *insns, size_t len); int patch_text(void *addr, u32 insn); +extern int riscv_patch_in_stop_machine; + #endif /* _ASM_RISCV_PATCH_H */ --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -15,11 +15,21 @@ int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) { mutex_lock(&text_mutex); + + /* + * The code sequences we use for ftrace can't be patched while the + * kernel is running, so we need to use stop_machine() to modify them + * for now. This doesn't play nice with text_mutex, we use this flag + * to elide the check. + */ + riscv_patch_in_stop_machine = true; + return 0; } int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) { + riscv_patch_in_stop_machine = false; mutex_unlock(&text_mutex); return 0; } @@ -109,9 +119,9 @@ int ftrace_init_nop(struct module *mod, { int out; - ftrace_arch_code_modify_prepare(); + mutex_lock(&text_mutex); out = ftrace_make_nop(mod, rec, MCOUNT_ADDR); - ftrace_arch_code_modify_post_process(); + mutex_unlock(&text_mutex); return out; } --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -11,6 +11,7 @@ #include #include #include +#include #include struct patch_insn { @@ -19,6 +20,8 @@ struct patch_insn { atomic_t cpu_count; }; +int riscv_patch_in_stop_machine = false; + #ifdef CONFIG_MMU static void *patch_map(void *addr, int fixmap) { @@ -55,8 +58,15 @@ static int patch_insn_write(void *addr, * Before reaching here, it was expected to lock the text_mutex * already, so we don't need to give another lock here and could * ensure that it was safe between each cores. + * + * We're currently using stop_machine() for ftrace & kprobes, and while + * that ensures text_mutex is held before installing the mappings it + * does not ensure text_mutex is held by the calling thread. That's + * safe but triggers a lockdep failure, so just elide it for that + * specific case. */ - lockdep_assert_held(&text_mutex); + if (!riscv_patch_in_stop_machine) + lockdep_assert_held(&text_mutex); if (across_pages) patch_map(addr + len, FIX_TEXT_POKE1); @@ -117,13 +127,25 @@ NOKPROBE_SYMBOL(patch_text_cb); int patch_text(void *addr, u32 insn) { + int ret; struct patch_insn patch = { .addr = addr, .insn = insn, .cpu_count = ATOMIC_INIT(0), }; - return stop_machine_cpuslocked(patch_text_cb, - &patch, cpu_online_mask); + /* + * kprobes takes text_mutex, before calling patch_text(), but as we call + * calls stop_machine(), the lockdep assertion in patch_insn_write() + * gets confused by the context in which the lock is taken. + * Instead, ensure the lock is held before calling stop_machine(), and + * set riscv_patch_in_stop_machine to skip the check in + * patch_insn_write(). + */ + lockdep_assert_held(&text_mutex); + riscv_patch_in_stop_machine = true; + ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask); + riscv_patch_in_stop_machine = false; + return ret; } NOKPROBE_SYMBOL(patch_text);