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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 18 Jun 2019 19:23:14 +0100 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5IINDrb52691166 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 18 Jun 2019 18:23:13 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5554111C05B; Tue, 18 Jun 2019 18:23:13 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E438611C050; Tue, 18 Jun 2019 18:23:12 +0000 (GMT) Received: from localhost (unknown [9.85.74.6]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 18 Jun 2019 18:23:12 +0000 (GMT) Date: Tue, 18 Jun 2019 23:53:11 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH 5/7] powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Masami Hiramatsu , Ingo Molnar , Michael Ellerman , Nicholas Piggin References: <186656540d3e6225abd98374e791a13d10d86fab.1560868106.git.naveen.n.rao@linux.vnet.ibm.com> <20190618114509.5b1acbe5@gandalf.local.home> <1560881411.p0i6a1dkwk.naveen@linux.ibm.com> In-Reply-To: <1560881411.p0i6a1dkwk.naveen@linux.ibm.com> User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT X-TM-AS-GCONF: 00 x-cbid: 19061818-0016-0000-0000-0000028A2FFF X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061818-0017-0000-0000-000032E7827C Message-Id: <1560881840.vz9llflvnf.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-18_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906180146 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Naveen N. Rao wrote: > Steven Rostedt wrote: >> On Tue, 18 Jun 2019 20:17:04 +0530 >> "Naveen N. Rao" wrote: >> >>> @@ -1551,7 +1551,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) >>> key.flags = end; /* overload flags, as it is unsigned long */ >>> >>> for (pg = ftrace_pages_start; pg; pg = pg->next) { >>> - if (end < pg->records[0].ip || >>> + if (end <= pg->records[0].ip || >> >> This breaks the algorithm. "end" is inclusive. That is, if you look for >> a single byte, where "start" and "end" are the same, and it happens to >> be the first ip on the pg page, it will be skipped, and not found. > > Thanks. It looks like I should be over-riding ftrace_location() instead. > I will update this patch. I think I will have ftrace own the two instruction range, regardless of whether the preceding instruction is a 'mflr r0' or not. This simplifies things and I don't see an issue with it as of now. I will do more testing to confirm. - Naveen --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -951,6 +951,16 @@ void arch_ftrace_update_code(int command) } #ifdef CONFIG_MPROFILE_KERNEL +/* + * We consider two instructions -- 'mflr r0', 'bl _mcount' -- to be part + * of ftrace. When checking for the first instruction, we want to include + * the next instruction in the range check. + */ +unsigned long ftrace_location(unsigned long ip) +{ + return ftrace_location_range(ip, ip + MCOUNT_INSN_SIZE); +} + /* Returns 1 if we patched in the mflr */ static int __ftrace_make_call_prep(struct dyn_ftrace *rec) { diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 21d8e201ee80..122e2bb4a739 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1573,7 +1573,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) * the function tracer. It checks the ftrace internal tables to * determine if the address belongs or not. */ -unsigned long ftrace_location(unsigned long ip) +unsigned long __weak ftrace_location(unsigned long ip) { return ftrace_location_range(ip, ip); }