From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3wz6cZ3ZfjzDr59 for ; Fri, 30 Jun 2017 03:49:50 +1000 (AEST) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v5THmoKl081891 for ; Thu, 29 Jun 2017 13:49:47 -0400 Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bd4aqnece-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 29 Jun 2017 13:49:47 -0400 Received: from localhost by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 30 Jun 2017 03:49:44 +1000 Received: from d23av06.au.ibm.com (d23av06.au.ibm.com [9.190.235.151]) by d23relay10.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v5THng2q1376560 for ; Fri, 30 Jun 2017 03:49:42 +1000 Received: from d23av06.au.ibm.com (localhost [127.0.0.1]) by d23av06.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v5THnf5m030503 for ; Fri, 30 Jun 2017 03:49:42 +1000 From: "Naveen N. Rao" To: Michael Ellerman Cc: Nicholas Piggin , Ananth N Mavinakayanahalli , Masami Hiramatsu , Anton Blanchard , linuxppc-dev@lists.ozlabs.org Subject: [PATCH v5 1/7] powerpc64/elfv1: Only dereference function descriptor for non-text symbols Date: Thu, 29 Jun 2017 23:19:14 +0530 In-Reply-To: References: In-Reply-To: References: Message-Id: <4bd8ff1d8855711d3bf8a11eecc8068e3aabac03.1498755960.git.naveen.n.rao@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Currently, we assume that the function pointer we receive in ppc_function_entry() points to a function descriptor. However, this is not always the case. In particular, assembly symbols without the right annotation do not have an associated function descriptor. Some of these symbols are added to the kprobe blacklist using _ASM_NOKPROBE_SYMBOL(). When such addresses are subsequently processed through arch_deref_entry_point() in populate_kprobe_blacklist(), we see the below errors during bootup: [ 0.663963] Failed to find blacklist at 7d9b02a648029b6c [ 0.663970] Failed to find blacklist at a14d03d0394a0001 [ 0.663972] Failed to find blacklist at 7d5302a6f94d0388 [ 0.663973] Failed to find blacklist at 48027d11e8610178 [ 0.663974] Failed to find blacklist at f8010070f8410080 [ 0.663976] Failed to find blacklist at 386100704801f89d [ 0.663977] Failed to find blacklist at 7d5302a6f94d00b0 Fix this by checking if the function pointer we receive in ppc_function_entry() already points to kernel text. If so, we just return it as is. If not, we assume that this is a function descriptor and proceed to dereference it. Suggested-by: Nicholas Piggin Reviewed-by: Nicholas Piggin Signed-off-by: Naveen N. Rao --- arch/powerpc/include/asm/code-patching.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h index abef812de7f8..5482928eea1b 100644 --- a/arch/powerpc/include/asm/code-patching.h +++ b/arch/powerpc/include/asm/code-patching.h @@ -83,8 +83,16 @@ static inline unsigned long ppc_function_entry(void *func) * On PPC64 ABIv1 the function pointer actually points to the * function's descriptor. The first entry in the descriptor is the * address of the function text. + * + * However, we may also receive pointer to an assembly symbol. To + * detect that, we first check if the function pointer we receive + * already points to kernel/module text and we only dereference it + * if it doesn't. */ - return ((func_descr_t *)func)->entry; + if (kernel_text_address((unsigned long)func)) + return (unsigned long)func; + else + return ((func_descr_t *)func)->entry; #else return (unsigned long)func; #endif -- 2.13.1