Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Subject: Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference
 count (semaphore)
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     mhiramat@kernel.org, peterz@infradead.org,
        srikar@linux.vnet.ibm.com, acme@kernel.org,
        ananth@linux.vnet.ibm.com, akpm@linux-foundation.org,
        alexander.shishkin@linux.intel.com, alexis.berlemont@gmail.com,
        corbet@lwn.net, dan.j.williams@intel.com,
        gregkh@linuxfoundation.org, huawei.libin@huawei.com,
        hughd@google.com, jack@suse.cz, jglisse@redhat.com,
        jolsa@redhat.com, kan.liang@intel.com,
        kirill.shutemov@linux.intel.com, kjlx@templeofstupid.com,
        kstewart@linuxfoundation.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com,
        milian.wolff@kdab.com, mingo@redhat.com, namhyung@kernel.org,
        naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com,
        pombredanne@nexb.com, rostedt@goodmis.org, tglx@linutronix.de,
        tmricht@linux.vnet.ibm.com, willy@infradead.org,
        yao.jin@linux.intel.com, fengguang.wu@intel.com,
        Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com>
 <20180313125603.19819-6-ravi.bangoria@linux.vnet.ibm.com>
 <20180315142120.GA19218@redhat.com> <20180315143044.GA19643@redhat.com>
Date:   Fri, 16 Mar 2018 14:58:55 +0530
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.6.0
MIME-Version: 1.0
In-Reply-To: <20180315143044.GA19643@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Message-Id: <3b303a2d-35dd-9178-fc03-de9f2d588797@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 03/15/2018 08:00 PM, Oleg Nesterov wrote:
> On 03/15, Oleg Nesterov wrote:
>>> +static struct vm_area_struct *
>>> +sdt_find_vma(struct mm_struct *mm, struct trace_uprobe *tu)
>>> +{
>>> +	struct vm_area_struct *tmp;
>>> +
>>> +	for (tmp = mm->mmap; tmp != NULL; tmp = tmp->vm_next)
>>> +		if (sdt_valid_vma(tu, tmp))
>>> +			return tmp;
>>> +
>>> +	return NULL;
>> I can't understand the logic... Lets ignore sdt_valid_vma() for now.
>> The caller has uprobe_map_info, why it can't simply do
>> vma = find_vma(uprobe_map_info->vaddr)? and then check sdt_valid_vma().
> Note to mention that sdt_find_vma() can return NULL but the callers do
> vma_offset_to_vaddr(vma) without any check.

If the "mm" we are passing to sdt_find_vma() is returned by
uprobe_build_map_info(ref_ctr_offset), sdt_find_vma() must
_not_ return NULL.

Thanks for the review,
Ravi