From patchwork Mon Mar 22 06:41:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 12153909 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04776C433E0 for ; Mon, 22 Mar 2021 06:42:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D054C61980 for ; Mon, 22 Mar 2021 06:42:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230295AbhCVGmN (ORCPT ); Mon, 22 Mar 2021 02:42:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:56160 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230241AbhCVGlq (ORCPT ); Mon, 22 Mar 2021 02:41:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EBA9561970; Mon, 22 Mar 2021 06:41:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616395306; bh=0+MBkE3MCP9qu3e+CtLb8WoQb39qbfkwrEHxIPqK/GQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Hbu62fHARhMhoHUr7w/DkD8gymVNHk+TZYFR4VLGeaxu5KmjToQJ8b4d96ScJf/c1 q4vSuGaxqag4tHHftW1DzyxcqJLThSR0D0PZdwa6Dc+7mwkXXG/dRIp8+RH0KyOl1W d2HnZm0XHJkbWPilHbRiKIC50fv1nvKEahHAp0mIp6T7mg8bX/qKosegWI0p7kcJ+/ A8PLCjZ9kjcna6ZyvHVi+vhF4OVT44FVjBMfbQCWDBNCq/t7bWuxVuxBK80FyTrSKF 6cjUjbsTLiaJJWtPQb6zJhAjRICZRVBbnAjVXDSeWLBwZJ62PlEmXkETzN5XDH/p37 0QATc2eLbYWNw== From: Masami Hiramatsu To: Steven Rostedt , Ingo Molnar Cc: X86 ML , Masami Hiramatsu , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, Josh Poimboeuf , linux-ia64@vger.kernel.org, Abhishek Sagar Subject: [PATCH -tip v4 10/12] x86/kprobes: Push a fake return address at kretprobe_trampoline Date: Mon, 22 Mar 2021 15:41:40 +0900 Message-Id: <161639530062.895304.16962383429668412873.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <161639518354.895304.15627519393073806809.stgit@devnote2> References: <161639518354.895304.15627519393073806809.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org This changes x86/kretprobe stack frame on kretprobe_trampoline a bit, which now push the kretprobe_trampoline as a fake return address at the bottom of the stack frame. With this fix, the ORC unwinder will see the kretprobe_trampoline as a return address. Signed-off-by: Masami Hiramatsu Suggested-by: Josh Poimboeuf --- arch/x86/kernel/kprobes/core.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 23255663c434..d7b90541eda1 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -782,28 +782,31 @@ asm( ".global kretprobe_trampoline\n" ".type kretprobe_trampoline, @function\n" "kretprobe_trampoline:\n" - /* We don't bother saving the ss register */ #ifdef CONFIG_X86_64 - " pushq %rsp\n" + /* Push fake return address to tell the unwinder it's a kretprobe */ + " pushq $kretprobe_trampoline\n" UNWIND_HINT_FUNC + /* Save the sp-8, this will be fixed later */ + " pushq %rsp\n" " pushfq\n" SAVE_REGS_STRING " movq %rsp, %rdi\n" " call trampoline_handler\n" - /* Replace saved sp with true return address. */ - " movq %rax, 19*8(%rsp)\n" RESTORE_REGS_STRING + " addq $8, %rsp\n" " popfq\n" #else - " pushl %esp\n" + /* Push fake return address to tell the unwinder it's a kretprobe */ + " pushl $kretprobe_trampoline\n" UNWIND_HINT_FUNC + /* Save the sp-4, this will be fixed later */ + " pushl %esp\n" " pushfl\n" SAVE_REGS_STRING " movl %esp, %eax\n" " call trampoline_handler\n" - /* Replace saved sp with true return address. */ - " movl %eax, 15*4(%esp)\n" RESTORE_REGS_STRING + " addl $4, %esp\n" " popfl\n" #endif " ret\n" @@ -814,8 +817,10 @@ NOKPROBE_SYMBOL(kretprobe_trampoline); /* * Called from kretprobe_trampoline */ -__used __visible void *trampoline_handler(struct pt_regs *regs) +__used __visible void trampoline_handler(struct pt_regs *regs) { + unsigned long *frame_pointer; + /* fixup registers */ regs->cs = __KERNEL_CS; #ifdef CONFIG_X86_32 @@ -823,8 +828,16 @@ __used __visible void *trampoline_handler(struct pt_regs *regs) #endif regs->ip = (unsigned long)&kretprobe_trampoline; regs->orig_ax = ~0UL; + regs->sp += sizeof(long); + frame_pointer = ((unsigned long *)®s->sp) + 1; - return (void *)kretprobe_trampoline_handler(regs, ®s->sp); + /* Replace fake return address with real one. */ + *frame_pointer = kretprobe_trampoline_handler(regs, frame_pointer); + /* + * Move flags to sp so that kretprobe_trapmoline can return + * right after popf. + */ + regs->sp = regs->flags; } NOKPROBE_SYMBOL(trampoline_handler);