From patchwork Thu Nov 14 16:26:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 11243999 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6DE8D109A for ; Thu, 14 Nov 2019 16:26:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5895020718 for ; Thu, 14 Nov 2019 16:26:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726444AbfKNQ0P (ORCPT ); Thu, 14 Nov 2019 11:26:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:55698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726251AbfKNQ0P (ORCPT ); Thu, 14 Nov 2019 11:26:15 -0500 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 AD35720715; Thu, 14 Nov 2019 16:26:13 +0000 (UTC) Date: Thu, 14 Nov 2019 11:26:12 -0500 From: Steven Rostedt To: LKML Cc: linux-sh@vger.kernel.org, Yoshinori Sato , Rich Felker , Sami Tolvanen Subject: [PATCH v2] fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub Message-ID: <20191114112612.3937f281@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org From: "Steven Rostedt (VMware)" The C compiler is allowing more checks to make sure that function pointers are assigned to the correct prototype function. Unfortunately, the function graph tracer uses a special name with its assigned ftrace_graph_return function pointer that maps to a stub function used by the function tracer (ftrace_stub). The ftrace_graph_return variable is compared to the ftrace_stub in some archs to know if the function graph tracer is enabled or not. This means we can not just simply create a new function stub that compares it without modifying all the archs. Instead, have the linker script create a function_graph_stub that maps to ftrace_stub, and this way we can define the prototype for it to match the prototype of ftrace_graph_return, and make the compiler checks all happy! Link: http://lkml.kernel.org/r/20191015090055.789a0aed@gandalf.local.home Reported-by: Sami Tolvanen Signed-off-by: Steven Rostedt (VMware) --- Changes from v1: When I ran this through the ktest crosstests.conf, it failed on superh, as superh uses the vmlinux.lds file from the kernel for its compression, it requires that it has a ftrace_stub() function defined there too. arch/sh/boot/compressed/misc.c | 5 +++++ include/asm-generic/vmlinux.lds.h | 17 ++++++++++++++--- kernel/trace/fgraph.c | 11 ++++++++--- 3 files changed, 27 insertions(+), 6 deletions(-) diff --git a/arch/sh/boot/compressed/misc.c b/arch/sh/boot/compressed/misc.c index c15cac9251b9..e69ec12cbbe6 100644 --- a/arch/sh/boot/compressed/misc.c +++ b/arch/sh/boot/compressed/misc.c @@ -111,6 +111,11 @@ void __stack_chk_fail(void) error("stack-protector: Kernel stack is corrupted\n"); } +/* Needed because vmlinux.lds.h references this */ +void ftrace_stub(void) +{ +} + #ifdef CONFIG_SUPERH64 #define stackalign 8 #else diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index dae64600ccbf..0f358be551cd 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -111,18 +111,29 @@ #ifdef CONFIG_FTRACE_MCOUNT_RECORD #ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY +/* + * Need to also make ftrace_graph_stub point to ftrace_stub + * so that the same stub location may have different protocols + * and not mess up with C verifiers. + */ #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__patchable_function_entries)) \ - __stop_mcount_loc = .; + __stop_mcount_loc = .; \ + ftrace_graph_stub = ftrace_stub; #else #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__mcount_loc)) \ - __stop_mcount_loc = .; + __stop_mcount_loc = .; \ + ftrace_graph_stub = ftrace_stub; #endif #else -#define MCOUNT_REC() +# ifdef CONFIG_FUNCTION_TRACER +# define MCOUNT_REC() ftrace_graph_stub = ftrace_stub; +# else +# define MCOUNT_REC() +# endif #endif #ifdef CONFIG_TRACE_BRANCH_PROFILING diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index 7950a0356042..fa3ce10d0405 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -332,9 +332,14 @@ int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace) return 0; } +/* + * Simply points to ftrace_stub, but with the proper protocol. + * Defined by the linker script in linux/vmlinux.lds.h + */ +extern void ftrace_graph_stub(struct ftrace_graph_ret *); + /* The callbacks that hook a function */ -trace_func_graph_ret_t ftrace_graph_return = - (trace_func_graph_ret_t)ftrace_stub; +trace_func_graph_ret_t ftrace_graph_return = ftrace_graph_stub; trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub; @@ -614,7 +619,7 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) goto out; ftrace_graph_active--; - ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub; + ftrace_graph_return = ftrace_graph_stub; ftrace_graph_entry = ftrace_graph_entry_stub; __ftrace_graph_entry = ftrace_graph_entry_stub; ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);