From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtUDFYKnw75OPpdaPay/9nG7GGkwvEYlz2zG4wFdbVCG4GzQDZaJCMmkPN9Bsdwjhz8ilWY ARC-Seal: i=1; a=rsa-sha256; t=1520945726; cv=none; d=google.com; s=arc-20160816; b=phhJj8ezD0ZK7/M9FAkVQ1okhKsJvJ2uXjv8j4D96EB1Uo0/8/amgsSMJ3pzODzDOs WXj6m4XZsXmkwIFf04Oita/ZfNtC6e8iuC3YKc3Zn9nl1uclAcRymhWDOrRONf4nfY4M FC6yTqbm3WwM236UPQMBGwIXwU7l+Tk1R+G/tsWQE0nXlYRMVNE4jIFhQ2B0J/sT+no7 Jc8F0W7Kt/epSSpMh4oA2USQ6L2UZ4Aduh/ij12MpABDHVcGfS0YwNXF8/RCRDyfUXth n4mtD88bq/eera3N5puBAY16jvjpmXBHPE0P+h8FoblmzUgZub2aC6pVU0jTxOvVaWgl 232w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:references:in-reply-to:date:subject:cc:to:from :arc-authentication-results; bh=hnD7mBfGc75S4c/jERf2u3y6Hf1yFZGwhcffD/hMB7s=; b=ft0o0JUW3tYsk16kPlqYMfJpXmq/0qxs+/fAKY9kb5XsCIVV+lDISVuJYYKgYa4tbW 6ZI7w9PfDokGplmh8VCEwWKTP9pjlpxrQepJDG6/LMC1Ao/QnNfVPIG3E+9yx73fydx5 mu0cNU+Mc2BC7FafUH7JYysV/Fs50Ndtk6VNzRi0MzHFzQWzxrXXcdRNnuhfFu+mGKFl WHY0FRcICnU0M7J5Nv/GPhgsvtNN7xXaPvsHYL3qBqBeS/bslR+AsH/RHJ0CX/y9b4yF EmyakNthRzxq89autfQ2Hy5LqPpnKqw16GLPd5J1ZC9qGz+oEwSLHdVWdAIqPNHVEiuh Ejrw== ARC-Authentication-Results: i=1; mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com From: Ravi Bangoria To: mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, srikar@linux.vnet.ibm.com Cc: 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 Subject: [PATCH 6/8] trace_uprobe/sdt: Fix multiple update of same reference counter Date: Tue, 13 Mar 2018 18:26:01 +0530 X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18031312-0016-0000-0000-00000530FAEA X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031312-0017-0000-0000-0000286E2CCD Message-Id: <20180313125603.19819-7-ravi.bangoria@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-13_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803130154 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594827186487084438?= X-GMAIL-MSGID: =?utf-8?q?1594827186487084438?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: For tiny binaries/libraries, different mmap regions points to the same file portion. In such cases, we may increment reference counter multiple times. But while de-registration, reference counter will get decremented only by once leaving reference counter > 0 even if no one is tracing on that marker. Ensure increment and decrement happens in sync by keeping list of mms in trace_uprobe. Increment reference counter only if mm is not present in the list and decrement only if mm is present in the list. Example # echo "p:sdt_tick/loop2 /tmp/tick:0x6e4(0x10036)" > uprobe_events Before patch: # perf stat -a -e sdt_tick:loop2 # /tmp/tick # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd 0000000: 02 . # pkill perf # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd 0000000: 01 . After patch: # perf stat -a -e sdt_tick:loop2 # /tmp/tick # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd 0000000: 01 . # pkill perf # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd 0000000: 00 . Signed-off-by: Ravi Bangoria --- kernel/trace/trace_uprobe.c | 105 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 103 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index b6c9b48..9bf3f7a 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -50,6 +50,11 @@ struct trace_uprobe_filter { struct list_head perf_events; }; +struct sdt_mm_list { + struct mm_struct *mm; + struct sdt_mm_list *next; +}; + /* * uprobe event core functions */ @@ -61,6 +66,8 @@ struct trace_uprobe { char *filename; unsigned long offset; unsigned long ref_ctr_offset; + struct sdt_mm_list *sml; + struct rw_semaphore sml_rw_sem; unsigned long nhit; struct trace_probe tp; }; @@ -274,6 +281,7 @@ static inline bool is_ret_probe(struct trace_uprobe *tu) if (is_ret) tu->consumer.ret_handler = uretprobe_dispatcher; init_trace_uprobe_filter(&tu->filter); + init_rwsem(&tu->sml_rw_sem); return tu; error: @@ -921,6 +929,74 @@ static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func, return trace_handle_return(s); } +static bool sdt_check_mm_list(struct trace_uprobe *tu, struct mm_struct *mm) +{ + struct sdt_mm_list *tmp = tu->sml; + + if (!tu->sml || !mm) + return false; + + while (tmp) { + if (tmp->mm == mm) + return true; + tmp = tmp->next; + } + + return false; +} + +static void sdt_add_mm_list(struct trace_uprobe *tu, struct mm_struct *mm) +{ + struct sdt_mm_list *tmp; + + tmp = kzalloc(sizeof(*tmp), GFP_KERNEL); + if (!tmp) + return; + + tmp->mm = mm; + tmp->next = tu->sml; + tu->sml = tmp; +} + +static void sdt_del_mm_list(struct trace_uprobe *tu, struct mm_struct *mm) +{ + struct sdt_mm_list *prev, *curr; + + if (!tu->sml) + return; + + if (tu->sml->mm == mm) { + curr = tu->sml; + tu->sml = tu->sml->next; + kfree(curr); + return; + } + + prev = tu->sml; + curr = tu->sml->next; + while (curr) { + if (curr->mm == mm) { + prev->next = curr->next; + kfree(curr); + return; + } + prev = curr; + curr = curr->next; + } +} + +static void sdt_flush_mm_list(struct trace_uprobe *tu) +{ + struct sdt_mm_list *next, *curr = tu->sml; + + while (curr) { + next = curr->next; + kfree(curr); + curr = next; + } + tu->sml = NULL; +} + static bool sdt_valid_vma(struct trace_uprobe *tu, struct vm_area_struct *vma) { unsigned long vaddr = vma_offset_to_vaddr(vma, tu->ref_ctr_offset); @@ -989,17 +1065,25 @@ static void sdt_increment_ref_ctr(struct trace_uprobe *tu) if (IS_ERR(info)) goto out; + down_write(&tu->sml_rw_sem); while (info) { + if (sdt_check_mm_list(tu, info->mm)) + goto cont; + down_write(&info->mm->mmap_sem); vma = sdt_find_vma(info->mm, tu); vaddr = vma_offset_to_vaddr(vma, tu->ref_ctr_offset); - sdt_update_ref_ctr(info->mm, vaddr, 1); + if (!sdt_update_ref_ctr(info->mm, vaddr, 1)) + sdt_add_mm_list(tu, info->mm); up_write(&info->mm->mmap_sem); + +cont: mmput(info->mm); info = uprobe_free_map_info(info); } + up_write(&tu->sml_rw_sem); out: uprobe_end_dup_mmap(); @@ -1020,8 +1104,16 @@ void trace_uprobe_mmap_callback(struct vm_area_struct *vma) !trace_probe_is_enabled(&tu->tp)) continue; + down_write(&tu->sml_rw_sem); + if (sdt_check_mm_list(tu, vma->vm_mm)) + goto cont; + vaddr = vma_offset_to_vaddr(vma, tu->ref_ctr_offset); - sdt_update_ref_ctr(vma->vm_mm, vaddr, 1); + if (!sdt_update_ref_ctr(vma->vm_mm, vaddr, 1)) + sdt_add_mm_list(tu, vma->vm_mm); + +cont: + up_write(&tu->sml_rw_sem); } mutex_unlock(&uprobe_lock); } @@ -1038,7 +1130,11 @@ static void sdt_decrement_ref_ctr(struct trace_uprobe *tu) if (IS_ERR(info)) goto out; + down_write(&tu->sml_rw_sem); while (info) { + if (!sdt_check_mm_list(tu, info->mm)) + goto cont; + down_write(&info->mm->mmap_sem); vma = sdt_find_vma(info->mm, tu); @@ -1046,9 +1142,14 @@ static void sdt_decrement_ref_ctr(struct trace_uprobe *tu) sdt_update_ref_ctr(info->mm, vaddr, -1); up_write(&info->mm->mmap_sem); + sdt_del_mm_list(tu, info->mm); + +cont: mmput(info->mm); info = uprobe_free_map_info(info); } + sdt_flush_mm_list(tu); + up_write(&tu->sml_rw_sem); out: uprobe_end_dup_mmap(); -- 1.8.3.1