From patchwork Thu Nov 9 23:48:29 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergey Senozhatsky X-Patchwork-Id: 10052139 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E44D8601EA for ; Thu, 9 Nov 2017 23:51:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D584F2B1F6 for ; Thu, 9 Nov 2017 23:51:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CA13B2B1FA; Thu, 9 Nov 2017 23:51:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,FREEMAIL_FROM,RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4506F2B1FE for ; Thu, 9 Nov 2017 23:51:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755409AbdKIXuz (ORCPT ); Thu, 9 Nov 2017 18:50:55 -0500 Received: from mail-pf0-f193.google.com ([209.85.192.193]:51483 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755383AbdKIXuw (ORCPT ); Thu, 9 Nov 2017 18:50:52 -0500 Received: by mail-pf0-f193.google.com with SMTP id j28so3101964pfk.8; Thu, 09 Nov 2017 15:50:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=gBEgXOJBzLHOxPJ8KiISypx9SW4dgzTQv6pFfa20/w4=; b=VkCc6weJqwrSRWclAYxQSMLVJIICzRe+5jC8ztEkdmVJ+24CNe/4jHTOsKae1/W3aE aDiDj4I5H98lCPfADB6Bw9N7zzLDFgniry6RmD7e/vnTLWGzxEOOulBMosQbZVxYTvyF vIn4yLXlTYwsnE6gQhw8B9UUPv7X2DNR4hQQLTEaPcQQhcNtNHXykXz0VBeVO2OG6XwW uKrBRV8kOvnsQXWj3QsTOIuVj3IpU8xQHmZ0YuQ5A0vRiT/xeHFukQ4PZgj5p36AyIw7 7/erskcEagNVpE5PIvTWj6YqzHUXdDoGhjQ+KFfsHEdWD0FOJAKzfUqUqvrwoucxQv6Z D9fg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=gBEgXOJBzLHOxPJ8KiISypx9SW4dgzTQv6pFfa20/w4=; b=dx8HsoxMse9Uszqsbxc26jgQMhBuh2RXpvfklq0B6KMHSD+2tI7P4QT1Hw9G/3OHW1 v3X/sI28Z1FT0LC5UKd/HL6T+2q39dxWIU/aQIvOkVWpOtQ1eL13Dr8wMm7r4PD5PPxQ hxB3QLex/sYx5f2Wef9WKZ2Z78ECRd3S3jZBvKOAu6BcYuWD7CPKOvJnxOSnQd6aXiZl o+sZu1RkOCmwgecBIiQwLSa35ja24vVPmsgln7/Z8Ls9oB+4Dk5UEf/qfIrW6eCYmC5X tlSlbHfIkjwZ5jMAE1Ee4lOyAZLHqpl28JcllWYzk4czSyvAY9NffZrfvHmIY5m2plS+ y2ig== X-Gm-Message-State: AJaThX7MpLIuEXYarwHE3ufvDPpxbmxXH4aopZ217hD0Mu3V5OSNm8AH na3rFpLHh8ZkJ2anMlxZlqQ= X-Google-Smtp-Source: ABhQp+S2+KZagx7Eu7kHnOE5hoy7P1XfkgqeQ1KWNWGDvg5ZeSqb12E8tMQbXRQyXK0PlMigZ1LQ8w== X-Received: by 10.98.17.7 with SMTP id z7mr2205572pfi.206.1510271451668; Thu, 09 Nov 2017 15:50:51 -0800 (PST) Received: from localhost.localdomain ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id t25sm13160477pfh.67.2017.11.09.15.50.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 Nov 2017 15:50:51 -0800 (PST) From: Sergey Senozhatsky To: Tony Luck , Fenghua Yu , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , James Bottomley Cc: Andrew Morton , Jessica Yu , Petr Mladek , Steven Rostedt , linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCHv4 5/6] symbol lookup: introduce dereference_symbol_descriptor() Date: Fri, 10 Nov 2017 08:48:29 +0900 Message-Id: <20171109234830.5067-6-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171109234830.5067-1-sergey.senozhatsky@gmail.com> References: <20171109234830.5067-1-sergey.senozhatsky@gmail.com> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP dereference_symbol_descriptor() invokes appropriate ARCH specific function descriptor dereference callbacks: - dereference_kernel_function_descriptor() if the pointer is a kernel symbol; - dereference_module_function_descriptor() if the pointer is a module symbol. This is the last step needed to make '%pS/%ps' smart enough to handle function descriptor dereference on affected ARCHs and to retire '%pF/%pf'. To refresh it: Some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers - the function pointer points to a function descriptor and we need to dereference it to get the actual function pointer. Function descriptors live in .opd elf section and all affected ARCHs (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. Signed-off-by: Sergey Senozhatsky --- Documentation/printk-formats.txt | 49 ++++++++++++++++------------------------ include/linux/kallsyms.h | 2 ++ kernel/kallsyms.c | 19 ++++++++++++++++ lib/vsprintf.c | 5 ++-- 4 files changed, 42 insertions(+), 33 deletions(-) diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt index 361789df51ec..2f17e684b72e 100644 --- a/Documentation/printk-formats.txt +++ b/Documentation/printk-formats.txt @@ -50,42 +50,31 @@ Symbols/Function Pointers :: - %pF versatile_init+0x0/0x110 - %pf versatile_init - %pS versatile_init+0x0/0x110 - %pSR versatile_init+0x9/0x110 - (with __builtin_extract_return_addr() translation) - %ps versatile_init - %pB prev_fn_of_versatile_init+0x88/0x88 - -The ``F`` and ``f`` specifiers are for printing function pointers, -for example, f->func, &gettimeofday. They have the same result as -``S`` and ``s`` specifiers. But they do an extra conversion on -ia64, ppc64 and parisc64 architectures where the function pointers -are actually function descriptors. - -The ``S`` and ``s`` specifiers can be used for printing symbols -from direct addresses, for example, __builtin_return_address(0), -(void *)regs->ip. They result in the symbol name with (``S``) or -without (``s``) offsets. If KALLSYMS are disabled then the symbol -address is printed instead. + %pS versatile_init+0x0/0x110 + %ps versatile_init + %pF versatile_init+0x0/0x110 + %pf versatile_init + %pSR versatile_init+0x9/0x110 + (with __builtin_extract_return_addr() translation) + %pB prev_fn_of_versatile_init+0x88/0x88 + +The ``S`` and ``s`` specifiers are used for printing a pointer in symbolic +format. They result in the symbol name with (``S``) or without (``s``) +offsets. If KALLSYMS are disabled then the symbol address is printed instead. + +Note, that the ``F`` and ``f`` specifiers are identical to ``S`` (``s``) +and thus deprecated. We have ``F`` and ``f`` because on ia64, ppc64 and +parisc64 function pointers are indirect and, in fact, are function +descriptors, which require additional dereferencing before we can lookup +the symbol. As of now, ``S`` and ``s`` perform dereferencing on those +platforms (when needed), so ``F`` and ``f`` exist for compatibility +reasons only. The ``B`` specifier results in the symbol name with offsets and should be used when printing stack backtraces. The specifier takes into consideration the effect of compiler optimisations which may occur when tail-call``s are used and marked with the noreturn GCC attribute. -Examples:: - - printk("Going to call: %pF\n", gettimeofday); - printk("Going to call: %pF\n", p->func); - printk("%s: called from %pS\n", __func__, (void *)_RET_IP_); - printk("%s: called from %pS\n", __func__, - (void *)__builtin_return_address(0)); - printk("Faulted at %pS\n", (void *)regs->ip); - printk(" %s%pB\n", (reliable ? "" : "? "), (void *)*stack); - - Kernel Pointers =============== diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index 11dd93e42580..73f7e874c3e1 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -16,6 +16,8 @@ struct module; +void *dereference_symbol_descriptor(void *ptr); + #ifdef CONFIG_KALLSYMS /* Lookup the address for a symbol. Returns 0 if not found. */ unsigned long kallsyms_lookup_name(const char *name); diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 1966fe1c2b57..18b3dffc4b84 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -411,6 +411,25 @@ static int __sprint_symbol(char *buffer, unsigned long address, return len; } +void *dereference_symbol_descriptor(void *ptr) +{ +#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR + struct module *mod; + + ptr = dereference_kernel_function_descriptor(ptr); + if (is_ksym_addr((unsigned long)ptr)) + return ptr; + + preempt_disable(); + mod = __module_address((unsigned long)ptr); + preempt_enable(); + + if (mod) + ptr = dereference_module_function_descriptor(mod, ptr); +#endif + return ptr; +} + /** * sprint_symbol - Look up a kernel symbol and return it in a text buffer * @buffer: buffer to be stored diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 1746bae94d41..16e2eefb0f79 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -40,7 +40,6 @@ #include "../mm/internal.h" /* For the trace_print_flags arrays */ #include /* for PAGE_SIZE */ -#include /* for dereference_function_descriptor() */ #include /* cpu_to_le16 */ #include @@ -1723,10 +1722,10 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, switch (*fmt) { case 'F': case 'f': - ptr = dereference_function_descriptor(ptr); - /* Fallthrough */ case 'S': case 's': + ptr = dereference_symbol_descriptor(ptr); + /* Fallthrough */ case 'B': return symbol_string(buf, end, ptr, spec, fmt); case 'R':