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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6DE23C433F5 for ; Tue, 5 Oct 2021 14:02:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 552BA61507 for ; Tue, 5 Oct 2021 14:02:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236503AbhJEOEX (ORCPT ); Tue, 5 Oct 2021 10:04:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:40900 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235524AbhJEOCi (ORCPT ); Tue, 5 Oct 2021 10:02:38 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D3AE61A10; Tue, 5 Oct 2021 13:58:31 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1mXkxi-0055qU-59; Tue, 05 Oct 2021 09:58:30 -0400 Message-ID: <20211005135829.993877823@goodmis.org> User-Agent: quilt/0.66 Date: Tue, 05 Oct 2021 09:57:57 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Masami Hiramatsu , Josh Poimboeuf , Andrii Nakryiko Subject: [for-linus][PATCH 24/27] x86/kprobes: Push a fake return address at kretprobe_trampoline References: <20211005135733.485175654@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masami Hiramatsu Change __kretprobe_trampoline() to push the address of the __kretprobe_trampoline() as a fake return address at the bottom of the stack frame. This fake return address will be replaced with the correct return address in the trampoline_handler(). With this change, the ORC unwinder can check whether the return address is modified by kretprobes or not. Link: https://lkml.kernel.org/r/163163054185.489837.14338744048957727386.stgit@devnote2 Signed-off-by: Masami Hiramatsu Suggested-by: Josh Poimboeuf Tested-by: Andrii Nakryiko Acked-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (VMware) --- arch/x86/kernel/kprobes/core.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index d1436d7463fd..7e1111c19605 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1022,28 +1022,33 @@ 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 a 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 + /* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */ + " addq $8, %rsp\n" " popfq\n" #else - " pushl %esp\n" + /* Push a 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 + /* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */ + " addl $4, %esp\n" " popfl\n" #endif " ret\n" @@ -1063,8 +1068,10 @@ STACK_FRAME_NON_STANDARD_FP(__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 @@ -1072,8 +1079,17 @@ __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 = ®s->sp + 1; + + /* Replace fake return address with real one. */ + *frame_pointer = kretprobe_trampoline_handler(regs, frame_pointer); - return (void *)kretprobe_trampoline_handler(regs, ®s->sp); + /* + * Copy FLAGS to 'pt_regs::sp' so that __kretprobe_trapmoline() + * can do RET right after POPF. + */ + regs->sp = regs->flags; } NOKPROBE_SYMBOL(trampoline_handler); -- 2.32.0