From patchwork Wed Dec 14 17:52:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13073319 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7495EC4167B for ; Wed, 14 Dec 2022 17:52:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237321AbiLNRwR (ORCPT ); Wed, 14 Dec 2022 12:52:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236910AbiLNRwQ (ORCPT ); Wed, 14 Dec 2022 12:52:16 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 05D9F1274D; Wed, 14 Dec 2022 09:52:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B2B33B819D8; Wed, 14 Dec 2022 17:52:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1F68C433EF; Wed, 14 Dec 2022 17:52:11 +0000 (UTC) Date: Wed, 14 Dec 2022 12:52:09 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Andrew Morton , Ross Zwisler , Tom Zanussi Subject: [PATCH] tracing: Add a way to filter function addresses to function names Message-ID: <20221214125209.09d736dd@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: "Steven Rostedt (Google)" There's been several times where an event records a function address in its field and I needed to filter on that address for a specific function name. It required looking up the function in kallsyms, finding its size, and doing a compare of "field >= function_start && field < function_end". But this would change from boot to boot and is unreliable in scripts. Also, it is useful to have this at boot up, where the addresses will not be known. For example, on the boot command line: trace_trigger="initcall_finish.traceoff if initcall_finish.function == acpi_init" To implement this, add a ".function" prefix, that will check that the field is of size long, and the only operations allowed (so far) are "==" and "!=". Signed-off-by: Steven Rostedt (Google) --- [ Resending due to claws-mail messing up the format of the original patch ] Documentation/trace/events.rst | 12 +++++ kernel/trace/trace_events.c | 2 +- kernel/trace/trace_events_filter.c | 79 +++++++++++++++++++++++++++++- 3 files changed, 91 insertions(+), 2 deletions(-) diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst index c47f381d0c00..d0fd5c7220b7 100644 --- a/Documentation/trace/events.rst +++ b/Documentation/trace/events.rst @@ -207,6 +207,18 @@ field name:: As the kernel will have to know how to retrieve the memory that the pointer is at from user space. +You can convert any long type to a function address and search by function name:: + + call_site.function == security_prepare_creds + +The above will filter when the field "call_site" falls on the address within +"security_prepare_creds". That is, it will compare the value of "call_site" and +the filter will return true if it is greater than or equal to the start of +the function "security_prepare_creds" and less than the end of that function. + +The ".function" postfix can only be attached to values of size long, and can only +be compared with "==" or "!=". + 5.2 Setting filters ------------------- diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 33e0b4f8ebe6..db6e2f399440 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2822,7 +2822,7 @@ static __init int setup_trace_triggers(char *str) if (!trigger) break; bootup_triggers[i].event = strsep(&trigger, "."); - bootup_triggers[i].trigger = strsep(&trigger, "."); + bootup_triggers[i].trigger = strsep(&trigger, ""); if (!bootup_triggers[i].trigger) break; } diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 96acc2b71ac7..eef6426051bb 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -64,6 +64,7 @@ enum filter_pred_fn { FILTER_PRED_FN_PCHAR_USER, FILTER_PRED_FN_PCHAR, FILTER_PRED_FN_CPU, + FILTER_PRED_FN_FUNCTION, FILTER_PRED_FN_, FILTER_PRED_TEST_VISITED, }; @@ -71,6 +72,7 @@ enum filter_pred_fn { struct filter_pred { enum filter_pred_fn fn_num; u64 val; + u64 val2; struct regex regex; unsigned short *ops; struct ftrace_event_field *field; @@ -103,6 +105,7 @@ struct filter_pred { C(INVALID_FILTER, "Meaningless filter expression"), \ C(IP_FIELD_ONLY, "Only 'ip' field is supported for function trace"), \ C(INVALID_VALUE, "Invalid value (did you forget quotes)?"), \ + C(NO_FUNCTION, "Function not found"), \ C(ERRNO, "Error"), \ C(NO_FILTER, "No filter found") @@ -876,6 +879,17 @@ static int filter_pred_comm(struct filter_pred *pred, void *event) return cmp ^ pred->not; } +/* Filter predicate for functions. */ +static int filter_pred_function(struct filter_pred *pred, void *event) +{ + unsigned long *addr = (unsigned long *)(event + pred->offset); + unsigned long start = (unsigned long)pred->val; + unsigned long end = (unsigned long)pred->val2; + int ret = *addr >= start && *addr < end; + + return pred->op == OP_EQ ? ret : !ret; +} + /* * regex_match_foo - Basic regex callbacks * @@ -1335,6 +1349,8 @@ static int filter_pred_fn_call(struct filter_pred *pred, void *event) return filter_pred_pchar(pred, event); case FILTER_PRED_FN_CPU: return filter_pred_cpu(pred, event); + case FILTER_PRED_FN_FUNCTION: + return filter_pred_function(pred, event); case FILTER_PRED_TEST_VISITED: return test_pred_visited_fn(pred, event); default: @@ -1350,8 +1366,13 @@ static int parse_pred(const char *str, void *data, struct trace_event_call *call = data; struct ftrace_event_field *field; struct filter_pred *pred = NULL; + unsigned long offset; + unsigned long size; + unsigned long ip; char num_buf[24]; /* Big enough to hold an address */ char *field_name; + char *name; + bool function = false; bool ustring = false; char q; u64 val; @@ -1393,6 +1414,12 @@ static int parse_pred(const char *str, void *data, i += len; } + /* See if the field is a user space string */ + if ((len = str_has_prefix(str + i, ".function"))) { + function = true; + i += len; + } + while (isspace(str[i])) i++; @@ -1423,7 +1450,57 @@ static int parse_pred(const char *str, void *data, pred->offset = field->offset; pred->op = op; - if (ftrace_event_is_function(call)) { + if (function) { + /* The field must be the same size as long */ + if (field->size != sizeof(long)) { + parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i); + goto err_free; + } + + /* Function only works with '==' or '!=' and an unquoted string */ + switch (op) { + case OP_NE: + case OP_EQ: + break; + default: + parse_error(pe, FILT_ERR_INVALID_OP, pos + i); + goto err_free; + } + + if (isdigit(str[i])) { + ret = kstrtol(num_buf, 0, &ip); + if (ret) { + parse_error(pe, FILT_ERR_INVALID_VALUE, pos + i); + goto err_free; + } + } else { + s = i; + for (; str[i] && !isspace(str[i]); i++) + ; + + len = i - s; + name = kmemdup_nul(str + s, len, GFP_KERNEL); + if (!name) + goto err_mem; + ip = kallsyms_lookup_name(name); + kfree(name); + if (!ip) { + parse_error(pe, FILT_ERR_NO_FUNCTION, pos + i); + goto err_free; + } + } + + /* Now find the function start and end address */ + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) { + parse_error(pe, FILT_ERR_NO_FUNCTION, pos + i); + goto err_free; + } + + pred->fn_num = FILTER_PRED_FN_FUNCTION; + pred->val = ip - offset; + pred->val2 = pred->val + size; + + } else if (ftrace_event_is_function(call)) { /* * Perf does things different with function events. * It only allows an "ip" field, and expects a string.