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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 8995CC5518B for ; Wed, 22 Apr 2020 16:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7112E2082E for ; Wed, 22 Apr 2020 16:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726547AbgDVQ1x (ORCPT ); Wed, 22 Apr 2020 12:27:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:42708 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726456AbgDVQ1w (ORCPT ); Wed, 22 Apr 2020 12:27:52 -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 D2EFC21655; Wed, 22 Apr 2020 16:27:51 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1jRIE2-000O5N-Ov; Wed, 22 Apr 2020 12:27:50 -0400 Message-Id: <20200422162750.638839749@goodmis.org> User-Agent: quilt/0.65 Date: Wed, 22 Apr 2020 12:25:42 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , tglx@linutronix.de, jpoimboe@redhat.com, x86@kernel.org, mhiramat@kernel.org, mbenes@suse.cz, jthierry@redhat.com, alexandre.chartre@oracle.com Subject: [PATCH 3/3] x86/ftrace: Do not jump to direct code in created trampolines References: <20200422162539.808362933@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" When creating a trampoline based on the ftrace_regs_caller code, nop out the jnz test that would jmup to the code that would return to a direct caller (stored in the ORIG_RAX field) and not back to the function that called it. Signed-off-by: Steven Rostedt (VMware) --- arch/x86/kernel/ftrace.c | 15 +++++++++++++++ arch/x86/kernel/ftrace_64.S | 1 + 2 files changed, 16 insertions(+) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 2e11250d5647..1db87ddb268b 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -286,6 +286,7 @@ extern void ftrace_regs_caller_ret(void); extern void ftrace_caller_end(void); extern void ftrace_caller_op_ptr(void); extern void ftrace_regs_caller_op_ptr(void); +extern void ftrace_regs_caller_jmp(void); /* movq function_trace_op(%rip), %rdx */ /* 0x48 0x8b 0x15 */ @@ -316,6 +317,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) unsigned long end_offset; unsigned long op_offset; unsigned long call_offset; + unsigned long jmp_offset; unsigned long offset; unsigned long npages; unsigned long size; @@ -333,11 +335,13 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) end_offset = (unsigned long)ftrace_regs_caller_end; op_offset = (unsigned long)ftrace_regs_caller_op_ptr; call_offset = (unsigned long)ftrace_regs_call; + jmp_offset = (unsigned long)ftrace_regs_caller_jmp; } else { start_offset = (unsigned long)ftrace_caller; end_offset = (unsigned long)ftrace_caller_end; op_offset = (unsigned long)ftrace_caller_op_ptr; call_offset = (unsigned long)ftrace_call; + jmp_offset = 0; } size = end_offset - start_offset; @@ -367,6 +371,17 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) if (WARN_ON(ret < 0)) goto fail; + /* No need to test direct calls on created trampolines */ + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + /* NOP the jnz 1f; but make sure it's a 2 byte jnz */ + ip = trampoline + (jmp_offset - start_offset); + if (WARN_ON(*(char *)ip != 0x75)) + goto fail; + ret = probe_kernel_read(ip, ideal_nops[2], 2); + if (ret < 0) + goto fail; + } + /* * The address of the ftrace_ops that is used for this trampoline * is stored at the end of the trampoline. This will be used to diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 0882758d165a..f72ef157feb3 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -241,6 +241,7 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL) */ movq ORIG_RAX(%rsp), %rax testq %rax, %rax +SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL) jnz 1f restore_mcount_regs -- 2.26.1