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#! /usr/bin/python3 # # argdist Trace a function and display a distribution of its # parameter values as a histogram or frequency count. # # USAGE: argdist [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-n COUNT] [-v] # [-c] [-T TOP] [-C specifier] [-H specifier] [-I header] # [-t TID] # # Licensed under the Apache License, Version 2.0 (the "License") # Copyright (C) 2016 Sasha Goldshtein. from bcc import BPF, USDT, StrcmpRewrite from time import sleep, strftime import argparse import re import traceback import os import sys class Probe(object): next_probe_index = 0 streq_index = 0 aliases = {"$PID": "(bpf_get_current_pid_tgid() >> 32)", "$COMM": "&val.name"} def _substitute_aliases(self, expr): if expr is None: return expr for alias, subst in Probe.aliases.items(): expr = expr.replace(alias, subst) return expr def _parse_signature(self): params = map(str.strip, self.signature.split(',')) self.param_types = {} for param in params: # If the type is a pointer, the * can be next to the # param name. Other complex types like arrays are not # supported right now. index = param.rfind('*') index = index if index != -1 else param.rfind(' ') param_type = param[0:index + 1].strip() param_name = param[index + 1:].strip() self.param_types[param_name] = param_type # Maintain list of user params. Then later decide to # switch to bpf_probe_read_kernel or bpf_probe_read_user. if "__user" in param_type.split(): self.probe_user_list.add(param_name) def _generate_entry(self): self.entry_probe_func = self.probe_func_name + "_entry" text = """ int PROBENAME(struct pt_regs *ctx SIGNATURE) { u64 __pid_tgid = bpf_get_current_pid_tgid(); u32 __pid = __pid_tgid; // lower 32 bits u32 __tgid = __pid_tgid >> 32; // upper 32 bits PID_FILTER TID_FILTER COLLECT return 0; } """ text = text.replace("PROBENAME", self.entry_probe_func) text = text.replace("SIGNATURE", "" if len(self.signature) == 0 else ", " + self.signature) text = text.replace("PID_FILTER", self._generate_pid_filter()) text = text.replace("TID_FILTER", self._generate_tid_filter()) collect = "" for pname in self.args_to_probe: param_hash = self.hashname_prefix + pname if pname == "__latency": collect += """ u64 __time = bpf_ktime_get_ns(); %s.update(&__pid, &__time); """ % param_hash else: collect += "%s.update(&__pid, &%s);\n" % \ (param_hash, pname) text = text.replace("COLLECT", collect) return text def _generate_entry_probe(self): # Any $entry(name) expressions result in saving that argument # when entering the function. self.args_to_probe = set() regex = r"\$entry\((\w+)\)" for expr in self.exprs: for arg in re.finditer(regex, expr): self.args_to_probe.add(arg.group(1)) for arg in re.finditer(regex, self.filter): self.args_to_probe.add(arg.group(1)) if any(map(lambda expr: "$latency" in expr, self.exprs)) or \ "$latency" in self.filter: self.args_to_probe.add("__latency") self.param_types["__latency"] = "u64" # nanoseconds for pname in self.args_to_probe: if pname not in self.param_types: raise ValueError("$entry(%s): no such param" % arg) self.hashname_prefix = "%s_param_" % self.probe_hash_name text = "" for pname in self.args_to_probe: # Each argument is stored in a separate hash that is # keyed by pid. text += "BPF_HASH(%s, u32, %s);\n" % \ (self.hashname_prefix + pname, self.param_types[pname]) text += self._generate_entry() return text def _generate_retprobe_prefix(self): # After we're done here, there are __%s_val variables for each # argument we needed to probe using $entry(name), and they all # have values (which isn't necessarily the case if we missed # the method entry probe). text = "" self.param_val_names = {} for pname in self.args_to_probe: val_name = "__%s_val" % pname text += "%s *%s = %s.lookup(&__pid);\n" % \ (self.param_types[pname], val_name, self.hashname_prefix + pname) text += "if (%s == 0) { return 0 ; }\n" % val_name self.param_val_names[pname] = val_name return text def _generate_comm_prefix(self): text = """ struct val_t { u32 pid; char name[sizeof(struct __string_t)]; }; struct val_t val = {.pid = (bpf_get_current_pid_tgid() >> 32) }; bpf_get_current_comm(&val.name, sizeof(val.name)); """ return text def _replace_entry_exprs(self): for pname, vname in self.param_val_names.items(): if pname == "__latency": entry_expr = "$latency" val_expr = "(bpf_ktime_get_ns() - *%s)" % vname else: entry_expr = "$entry(%s)" % pname val_expr = "(*%s)" % vname for i in range(0, len(self.exprs)): self.exprs[i] = self.exprs[i].replace( entry_expr, val_expr) self.filter = self.filter.replace(entry_expr, val_expr) def _attach_entry_probe(self): if self.is_user: self.bpf.attach_uprobe(name=self.library, sym=self.function, fn_name=self.entry_probe_func, pid=self.pid or -1) else: self.bpf.attach_kprobe(event=self.function, fn_name=self.entry_probe_func) def _bail(self, error): raise ValueError("error parsing probe '%s': %s" % (self.raw_spec, error)) def _validate_specifier(self): # Everything after '#' is the probe label, ignore it spec = self.raw_spec.split('#')[0] parts = spec.strip().split(':') if len(parts) < 3: self._bail("at least the probe type, library, and " + "function signature must be specified") if len(parts) > 6: self._bail("extraneous ':'-separated parts detected") if parts[0] not in ["r", "p", "t", "u"]: self._bail("probe type must be 'p', 'r', 't', or 'u'" + " but got '%s'" % parts[0]) if re.match(r"\S+\(.*\)", parts[2]) is None: self._bail(("function signature '%s' has an invalid " + "format") % parts[2]) def _parse_expr_types(self, expr_types): if len(expr_types) == 0: self._bail("no expr types specified") self.expr_types = expr_types.split(',') def _parse_exprs(self, exprs): if len(exprs) == 0: self._bail("no exprs specified") self.exprs = exprs.split(',') def _make_valid_identifier(self, ident): return re.sub(r'[^A-Za-z0-9_]', '_', ident) def __init__(self, tool, type, specifier): self.usdt_ctx = None self.streq_functions = "" self.pid = tool.args.pid self.tid = tool.args.tid self.cumulative = tool.args.cumulative or False self.raw_spec = specifier self.probe_user_list = set() self.bin_cmp = False self._validate_specifier() spec_and_label = specifier.split('#') self.label = spec_and_label[1] \ if len(spec_and_label) == 2 else None parts = spec_and_label[0].strip().split(':') self.type = type # hist or freq self.probe_type = parts[0] fparts = parts[2].split('(') self.function = fparts[0].strip() if self.probe_type == "t": self.library = "" # kernel self.tp_category = parts[1] self.tp_event = self.function elif self.probe_type == "u": self.library = parts[1] self.probe_func_name = self._make_valid_identifier( "%s_probe%d" % (self.function, Probe.next_probe_index)) self._enable_usdt_probe() else: self.library = parts[1] self.is_user = len(self.library) > 0 self.signature = fparts[1].strip()[:-1] self._parse_signature() # If the user didn't specify an expression to probe, we probe # the retval in a ret probe, or simply the value "1" otherwise. self.is_default_expr = len(parts) < 5 if not self.is_default_expr: self._parse_expr_types(parts[3]) self._parse_exprs(parts[4]) if len(self.exprs) != len(self.expr_types): self._bail("mismatched # of exprs and types") if self.type == "hist" and len(self.expr_types) > 1: self._bail("histograms can only have 1 expr") else: if not self.probe_type == "r" and self.type == "hist": self._bail("histograms must have expr") self.expr_types = \ ["u64" if not self.probe_type == "r" else "int"] self.exprs = \ ["1" if not self.probe_type == "r" else "$retval"] self.filter = "" if len(parts) != 6 else parts[5] self._substitute_exprs() # Do we need to attach an entry probe so that we can collect an # argument that is required for an exit (return) probe? def check(expr): keywords = ["$entry", "$latency"] return any(map(lambda kw: kw in expr, keywords)) self.entry_probe_required = self.probe_type == "r" and \ (any(map(check, self.exprs)) or check(self.filter)) self.probe_func_name = self._make_valid_identifier( "%s_probe%d" % (self.function, Probe.next_probe_index)) self.probe_hash_name = self._make_valid_identifier( "%s_hash%d" % (self.function, Probe.next_probe_index)) Probe.next_probe_index += 1 def _enable_usdt_probe(self): self.usdt_ctx = USDT(path=self.library, pid=self.pid) self.usdt_ctx.enable_probe( self.function, self.probe_func_name) def _substitute_exprs(self): def repl(expr): expr = self._substitute_aliases(expr) rdict = StrcmpRewrite.rewrite_expr(expr, self.bin_cmp, self.library, self.probe_user_list, self.streq_functions, Probe.streq_index) expr = rdict["expr"] self.streq_functions = rdict["streq_functions"] Probe.streq_index = rdict["probeid"] return expr.replace("$retval", "PT_REGS_RC(ctx)") for i in range(0, len(self.exprs)): self.exprs[i] = repl(self.exprs[i]) self.filter = repl(self.filter) def _is_string(self, expr_type): return expr_type == "char*" or expr_type == "char *" def _generate_hash_field(self, i): if self._is_string(self.expr_types[i]): return "struct __string_t v%d;\n" % i else: return "%s v%d;\n" % (self.expr_types[i], i) def _generate_usdt_arg_assignment(self, i): expr = self.exprs[i] if self.probe_type == "u" and expr[0:3] == "arg": arg_index = int(expr[3]) arg_ctype = self.usdt_ctx.get_probe_arg_ctype( self.function, arg_index - 1) return (" %s %s = 0;\n" + " bpf_usdt_readarg(%s, ctx, &%s);\n") \ % (arg_ctype, expr, expr[3], expr) else: return "" def _generate_field_assignment(self, i): text = self._generate_usdt_arg_assignment(i) if self._is_string(self.expr_types[i]): if self.is_user or \ self.exprs[i] in self.probe_user_list: probe_readfunc = "bpf_probe_read_user" else: probe_readfunc = "bpf_probe_read_kernel" return (text + " %s(&__key.v%d.s," + " sizeof(__key.v%d.s), (void *)%s);\n") % \ (probe_readfunc, i, i, self.exprs[i]) else: return text + " __key.v%d = %s;\n" % \ (i, self.exprs[i]) def _generate_hash_decl(self): if self.type == "hist": return "BPF_HISTOGRAM(%s, %s);" % \ (self.probe_hash_name, self.expr_types[0]) else: text = "struct %s_key_t {\n" % self.probe_hash_name for i in range(0, len(self.expr_types)): text += self._generate_hash_field(i) text += "};\n" text += "BPF_HASH(%s, struct %s_key_t, u64);\n" % \ (self.probe_hash_name, self.probe_hash_name) return text def _generate_key_assignment(self): if self.type == "hist": return self._generate_usdt_arg_assignment(0) + \ ("%s __key = %s;\n" % (self.expr_types[0], self.exprs[0])) else: text = "struct %s_key_t __key = {};\n" % \ self.probe_hash_name for i in range(0, len(self.exprs)): text += self._generate_field_assignment(i) return text def _generate_hash_update(self): if self.type == "hist": return "%s.atomic_increment(bpf_log2l(__key));" % \ self.probe_hash_name else: return "%s.atomic_increment(__key);" % \ self.probe_hash_name def _generate_pid_filter(self): # Kernel probes need to explicitly filter pid, because the # attach interface doesn't support pid filtering if self.pid is not None and not self.is_user: return "if (__tgid != %d) { return 0; }" % self.pid else: return "" def _generate_tid_filter(self): if self.tid is not None and not self.is_user: return "if (__pid != %d) { return 0; }" % self.tid else: return "" def generate_text(self): program = "" probe_text = """ DATA_DECL """ + ( "TRACEPOINT_PROBE(%s, %s)" % (self.tp_category, self.tp_event) if self.probe_type == "t" else "int PROBENAME(struct pt_regs *ctx SIGNATURE)") + """ { u64 __pid_tgid = bpf_get_current_pid_tgid(); u32 __pid = __pid_tgid; // lower 32 bits u32 __tgid = __pid_tgid >> 32; // upper 32 bits PID_FILTER TID_FILTER PREFIX KEY_EXPR if (!(FILTER)) return 0; COLLECT return 0; } """ prefix = "" signature = "" # If any entry arguments are probed in a ret probe, we need # to generate an entry probe to collect them if self.entry_probe_required: program += self._generate_entry_probe() prefix += self._generate_retprobe_prefix() # Replace $entry(paramname) with a reference to the # value we collected when entering the function: self._replace_entry_exprs() if self.probe_type == "p" and len(self.signature) > 0: # Only entry uprobes/kprobes can have user-specified # signatures. Other probes force it to (). signature = ", " + self.signature # If COMM is specified prefix with code to get process name if self.exprs.count(self.aliases['$COMM']): prefix += self._generate_comm_prefix() program += probe_text.replace("PROBENAME", self.probe_func_name) program = program.replace("SIGNATURE", signature) program = program.replace("PID_FILTER", self._generate_pid_filter()) program = program.replace("TID_FILTER", self._generate_tid_filter()) decl = self._generate_hash_decl() key_expr = self._generate_key_assignment() collect = self._generate_hash_update() program = program.replace("DATA_DECL", decl) program = program.replace("KEY_EXPR", key_expr) program = program.replace("FILTER", "1" if len(self.filter) == 0 else self.filter) program = program.replace("COLLECT", collect) program = program.replace("PREFIX", prefix) return self.streq_functions + program def _attach_u(self): libpath = BPF.find_library(self.library) if libpath is None: libpath = BPF.find_exe(self.library) if libpath is None or len(libpath) == 0: self._bail("unable to find library %s" % self.library) if self.probe_type == "r": self.bpf.attach_uretprobe(name=libpath, sym=self.function, fn_name=self.probe_func_name, pid=self.pid or -1) else: self.bpf.attach_uprobe(name=libpath, sym=self.function, fn_name=self.probe_func_name, pid=self.pid or -1) def _attach_k(self): if self.probe_type == "t": pass # Nothing to do for tracepoints elif self.probe_type == "r": self.bpf.attach_kretprobe(event=self.function, fn_name=self.probe_func_name) else: self.bpf.attach_kprobe(event=self.function, fn_name=self.probe_func_name) def attach(self, bpf): self.bpf = bpf if self.probe_type == "u": return if self.is_user: self._attach_u() else: self._attach_k() if self.entry_probe_required: self._attach_entry_probe() # Check whether hash table batch ops is supported if self.type == "freq" and self.bpf.kernel_struct_has_field( b'bpf_map_ops', b'map_lookup_and_delete_batch') == 1: self.htab_batch_ops = True else: self.htab_batch_ops = False def _v2s(self, v): # Most fields can be converted with plain str(), but strings # are wrapped in a __string_t which has an .s field if "__string_t" in type(v).__name__: return str(v.s) return str(v) def _display_expr(self, i): # Replace ugly latency calculation with $latency expr = self.exprs[i].replace( "(bpf_ktime_get_ns() - *____latency_val)", "$latency") # Replace alias values back with the alias name for alias, subst in Probe.aliases.items(): expr = expr.replace(subst, alias) # Replace retval expression with $retval expr = expr.replace("PT_REGS_RC(ctx)", "$retval") # Replace ugly (*__param_val) expressions with param name return re.sub(r"\(\*__(\w+)_val\)", r"\1", expr) def _display_key(self, key): if self.is_default_expr: if not self.probe_type == "r": return "total calls" else: return "retval = %s" % str(key.v0) else: # The key object has v0, ..., vk fields containing # the values of the expressions from self.exprs def str_i(i): key_i = self._v2s(getattr(key, "v%d" % i)) return "%s = %s" % \ (self._display_expr(i), key_i) return ", ".join(map(str_i, range(0, len(self.exprs)))) def display(self, top): data = self.bpf.get_table(self.probe_hash_name) if self.type == "freq": print(self.label or self.raw_spec) print("\t%-10s %s" % ("COUNT", "EVENT")) sdata = sorted(data.items_lookup_batch() if self.htab_batch_ops else data.items(), key=lambda p: p[1].value) if top is not None: sdata = sdata[-top:] for key, value in sdata: # Print some nice values if the user didn't # specify an expression to probe if self.is_default_expr: if not self.probe_type == "r": key_str = "total calls" else: key_str = "retval = %s" % \ self._v2s(key.v0) else: key_str = self._display_key(key) print("\t%-10s %s" % (str(value.value), key_str)) elif self.type == "hist": label = self.label or (self._display_expr(0) if not self.is_default_expr else "retval") data.print_log2_hist(val_type=label) if not self.cumulative: if self.htab_batch_ops: data.items_delete_batch() else: data.clear() def __str__(self): return self.label or self.raw_spec class Tool(object): examples = """ Probe specifier syntax: {p,r,t,u}:{[library],category}:function(signature):type[,type...]:expr[,expr...][:filter]][#label] Where: p,r,t,u -- probe at function entry, function exit, kernel tracepoint, or USDT probe in exit probes: can use $retval, $entry(param), $latency library -- the library that contains the function (leave empty for kernel functions) category -- the category of the kernel tracepoint (e.g. net, sched) function -- the function name to trace (or tracepoint name) signature -- the function's parameters, as in the C header type -- the type of the expression to collect (supports multiple) expr -- the expression to collect (supports multiple) filter -- the filter that is applied to collected values label -- the label for this probe in the resulting output EXAMPLES: argdist -H 'p::__kmalloc(u64 size):u64:size' Print a histogram of allocation sizes passed to kmalloc argdist -p 1005 -C 'p:c:malloc(size_t size):size_t:size:size==16' Print a frequency count of how many times process 1005 called malloc with an allocation size of 16 bytes argdist -C 'r:c:gets():char*:(char*)$retval#snooped strings' Snoop on all strings returned by gets() argdist -H 'r::__kmalloc(size_t size):u64:$latency/$entry(size)#ns per byte' Print a histogram of nanoseconds per byte from kmalloc allocations argdist -C 'p::__kmalloc(size_t sz, gfp_t flags):size_t:sz:flags&GFP_ATOMIC' Print frequency count of kmalloc allocation sizes that have GFP_ATOMIC argdist -p 1005 -C 'p:c:write(int fd):int:fd' -T 5 Print frequency counts of how many times writes were issued to a particular file descriptor number, in process 1005, but only show the top 5 busiest fds argdist -p 1005 -H 'r:c:read()' Print a histogram of results (sizes) returned by read() in process 1005 argdist -C 'r::__vfs_read():u32:$PID:$latency > 100000' Print frequency of reads by process where the latency was >0.1ms argdist -C 'r::__vfs_read():u32:$COMM:$latency > 100000' Print frequency of reads by process name where the latency was >0.1ms argdist -H 'r::__vfs_read(void *file, void *buf, size_t count):size_t: $entry(count):$latency > 1000000' Print a histogram of read sizes that were longer than 1ms argdist -H \\ 'p:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1' Print a histogram of buffer sizes passed to write() across all processes, where the file descriptor was 1 (STDOUT) argdist -C 'p:c:fork()#fork calls' Count fork() calls in libc across all processes Can also use funccount.py, which is easier and more flexible argdist -H 't:block:block_rq_complete():u32:args->nr_sector' Print histogram of number of sectors in completing block I/O requests argdist -C 't:irq:irq_handler_entry():int:args->irq' Aggregate interrupts by interrupt request (IRQ) argdist -C 'u:pthread:pthread_start():u64:arg2' -p 1337 Print frequency of function addresses used as a pthread start function, relying on the USDT pthread_start probe in process 1337 argdist -H 'p:c:sleep(u32 seconds):u32:seconds' \\ -H 'p:c:nanosleep(struct timespec *req):long:req->tv_nsec' Print histograms of sleep() and nanosleep() parameter values argdist -p 2780 -z 120 \\ -C 'p:c:write(int fd, char* buf, size_t len):char*:buf:fd==1' Spy on writes to STDOUT performed by process 2780, up to a string size of 120 characters argdist -I 'kernel/sched/sched.h' \\ -C 'p::__account_cfs_rq_runtime(struct cfs_rq *cfs_rq):s64:cfs_rq->runtime_remaining' Trace on the cfs scheduling runqueue remaining runtime. The struct cfs_rq is defined in kernel/sched/sched.h which is in kernel source tree and not in kernel-devel package. So this command needs to run at the kernel source tree root directory so that the added header file can be found by the compiler. """ def __init__(self): parser = argparse.ArgumentParser(description="Trace a " + "function and display a summary of its parameter values.", formatter_class=argparse.RawDescriptionHelpFormatter, epilog=Tool.examples) parser.add_argument("-p", "--pid", type=int, help="id of the process to trace (optional)") parser.add_argument("-t", "--tid", type=int, help="id of the thread to trace (optional)") parser.add_argument("-z", "--string-size", default=80, type=int, help="maximum string size to read from char* arguments") parser.add_argument("-i", "--interval", default=1, type=int, help="output interval, in seconds (default 1 second)") parser.add_argument("-d", "--duration", type=int, help="total duration of trace, in seconds") parser.add_argument("-n", "--number", type=int, dest="count", help="number of outputs") parser.add_argument("-v", "--verbose", action="store_true", help="print resulting BPF program code before executing") parser.add_argument("-c", "--cumulative", action="store_true", help="do not clear histograms and freq counts at " + "each interval") parser.add_argument("-T", "--top", type=int, help="number of top results to show (not applicable to " + "histograms)") parser.add_argument("-H", "--histogram", action="append", dest="histspecifier", metavar="specifier", help="probe specifier to capture histogram of " + "(see examples below)") parser.add_argument("-C", "--count", action="append", dest="countspecifier", metavar="specifier", help="probe specifier to capture count of " + "(see examples below)") parser.add_argument("-I", "--include", action="append", metavar="header", help="additional header files to include in the BPF program " "as either full path, " "or relative to relative to current working directory, " "or relative to default kernel header search path") parser.add_argument("--ebpf", action="store_true", help=argparse.SUPPRESS) self.args = parser.parse_args() self.usdt_ctx = None def _create_probes(self): self.probes = [] for specifier in (self.args.countspecifier or []): self.probes.append(Probe(self, "freq", specifier)) for histspecifier in (self.args.histspecifier or []): self.probes.append(Probe(self, "hist", histspecifier)) if len(self.probes) == 0: print("at least one specifier is required") exit(1) def _generate_program(self): bpf_source = """ struct __string_t { char s[%d]; }; #include <uapi/linux/ptrace.h> """ % self.args.string_size for include in (self.args.include or []): if include.startswith((".", "/")): include = os.path.abspath(include) bpf_source += "#include \"%s\"\n" % include else: bpf_source += "#include <%s>\n" % include bpf_source += BPF.generate_auto_includes( map(lambda p: p.raw_spec, self.probes)) for probe in self.probes: bpf_source += probe.generate_text() if self.args.verbose: for text in [probe.usdt_ctx.get_text() for probe in self.probes if probe.usdt_ctx]: print(text) if self.args.verbose or self.args.ebpf: print(bpf_source) if self.args.ebpf: exit() usdt_contexts = [probe.usdt_ctx for probe in self.probes if probe.usdt_ctx] self.bpf = BPF(text=bpf_source, usdt_contexts=usdt_contexts) def _attach(self): for probe in self.probes: probe.attach(self.bpf) if self.args.verbose: print("open uprobes: %s" % list(self.bpf.uprobe_fds.keys())) print("open kprobes: %s" % list(self.bpf.kprobe_fds.keys())) def _main_loop(self): count_so_far = 0 seconds = 0 while True: try: sleep(self.args.interval) seconds += self.args.interval except KeyboardInterrupt: exit() print("[%s]" % strftime("%H:%M:%S")) for probe in self.probes: probe.display(self.args.top) count_so_far += 1 if self.args.count is not None and \ count_so_far >= self.args.count: exit() if self.args.duration and \ seconds >= self.args.duration: exit() def run(self): try: self._create_probes() self._generate_program() self._attach() self._main_loop() except: exc_info = sys.exc_info() sys_exit = exc_info[0] is SystemExit if self.args.verbose: traceback.print_exc() elif not sys_exit: print(exc_info[1]) exit(0 if sys_exit else 1) if __name__ == "__main__": Tool().run()