Add profile probe provider

README.md

@@ -110,6 +110,12 @@ Attach script to a statically defined tracepoint in the kernel:
 
 Tracepoints are guaranteed to be stable between kernel versions, unlike kprobes.
 
+### timers
+Run the script at specified time intervals:
+
+`profile:hz:99 { ... }`
+`profile:ms:10 { ... }`
+
 ### Multiple attachment points
 More than one function/tracepoint can be specified for a single probe:
 

src/ast.cpp

@@ -104,6 +104,8 @@ std::string AttachPoint::name(const std::string &attach_point) const
     n += ":" + target;
   if (attach_point != "")
     n += ":" + attach_point;
+  if (freq != 0)
+    n += ":" + std::to_string(freq);
   return n;
 }
 
@@ -117,6 +119,8 @@ std::string Probe::name() const
       n += ":" + attach_point->target;
     if (attach_point->func != "")
       n += ":" + attach_point->func;
+    if (attach_point->freq != 0)
+      n += ":" + std::to_string(attach_point->freq);
     n += ",";
   }
   return n.substr(0, n.size()-1);

src/ast.h

@@ -147,10 +147,15 @@ public:
               const std::string &target,
               const std::string &func)
     : provider(provider), target(target), func(func) { }
+  AttachPoint(const std::string &provider,
+              const std::string &target,
+              int freq)
+    : provider(provider), target(target), freq(freq) { }
 
   std::string provider;
   std::string target;
   std::string func;
+  int freq = 0;
 
   void accept(Visitor &v) override;
   std::string name(const std::string &attach_point) const;

src/attached_probe.cpp

@@ -6,8 +6,10 @@
 
 #include "attached_probe.h"
 #include "bcc_syms.h"
+#include "common.h"
 #include "libbpf.h"
 #include "perf_reader.h"
+#include <linux/perf_event.h>
 
 namespace bpftrace {
 
@@ -32,6 +34,7 @@ bpf_prog_type progtype(ProbeType t)
     case ProbeType::uprobe:     return BPF_PROG_TYPE_KPROBE; break;
     case ProbeType::uretprobe:  return BPF_PROG_TYPE_KPROBE; break;
     case ProbeType::tracepoint: return BPF_PROG_TYPE_TRACEPOINT; break;
+    case ProbeType::profile:      return BPF_PROG_TYPE_PERF_EVENT; break;
     default: abort();
   }
 }
@@ -54,6 +57,9 @@ AttachedProbe::AttachedProbe(Probe &probe, std::tuple<uint8_t *, uintptr_t> &fun
     case ProbeType::tracepoint:
       attach_tracepoint();
       break;
+    case ProbeType::profile:
+      attach_profile();
+      break;
     default:
       abort();
   }
@@ -62,6 +68,7 @@ AttachedProbe::AttachedProbe(Probe &probe, std::tuple<uint8_t *, uintptr_t> &fun
 AttachedProbe::~AttachedProbe()
 {
   close(progfd_);
+  if (perf_reader_)
     perf_reader_free(perf_reader_);
   int err = 0;
   switch (probe_.type)
@@ -77,6 +84,9 @@ AttachedProbe::~AttachedProbe()
     case ProbeType::tracepoint:
       err = bpf_detach_tracepoint(probe_.path.c_str(), eventname().c_str());
       break;
+    case ProbeType::profile:
+      err = detach_profile();
+      break;
     default:
       abort();
   }
@@ -206,4 +216,59 @@ void AttachedProbe::attach_tracepoint()
     throw std::runtime_error("Error attaching probe: " + probe_.name);
 }
 
+void AttachedProbe::attach_profile()
+{
+  int pid = -1;
+  int group_fd = -1;
+
+  uint64_t period, freq;
+  if (probe_.path == "hz")
+  {
+    period = 0;
+    freq = probe_.freq;
+  }
+  else if (probe_.path == "s")
+  {
+    period = probe_.freq * 1e9;
+    freq = 0;
+  }
+  else if (probe_.path == "ms")
+  {
+    period = probe_.freq * 1e6;
+    freq = 0;
+  }
+  else if (probe_.path == "us")
+  {
+    period = probe_.freq * 1e3;
+    freq = 0;
+  }
+  else
+  {
+    abort();
+  }
+
+  std::vector<int> cpus = ebpf::get_online_cpus();
+  for (int cpu : cpus)
+  {
+    int perf_event_fd = bpf_attach_perf_event(progfd_, PERF_TYPE_SOFTWARE,
+        PERF_COUNT_SW_CPU_CLOCK, period, freq, pid, cpu, group_fd);
+
+    if (perf_event_fd < 0)
+      throw std::runtime_error("Error attaching probe: " + probe_.name);
+
+    perf_event_fds_.push_back(perf_event_fd);
+  }
+}
+
+int AttachedProbe::detach_profile()
+{
+  for (int perf_event_fd : perf_event_fds_)
+  {
+    int err = bpf_close_perf_event_fd(perf_event_fd);
+    if (err)
+      return err;
+  }
+  return 0;
+}
+
 } // namespace bpftrace

src/attached_probe.h

@@ -26,10 +26,13 @@ private:
   void attach_kprobe();
   void attach_uprobe();
   void attach_tracepoint();
+  void attach_profile();
+  int detach_profile();
 
   Probe &probe_;
   std::tuple<uint8_t *, uintptr_t> &func_;
-  void *perf_reader_;
+  std::vector<int> perf_event_fds_;
+  void *perf_reader_ = nullptr;
   int progfd_;
 };
 

src/bpftrace.cpp

@@ -78,6 +78,7 @@ int BPFtrace::add_probe(ast::Probe &p)
       probe.type = probetype(attach_point->provider);
       probe.prog_name = p.name();
       probe.name = attach_point->name(func);
+      probe.freq = attach_point->freq;
       probes_.push_back(probe);
     }
   }

src/parser.yy

@@ -121,6 +121,7 @@ attach_points : attach_points "," attach_point { $$ = $1; $1->push_back($3); }
 attach_point : IDENT               { $$ = new ast::AttachPoint($1); }
              | IDENT ":" wildcard  { $$ = new ast::AttachPoint($1, $3); }
              | IDENT PATH wildcard { $$ = new ast::AttachPoint($1, $2.substr(1, $2.size()-2), $3); }
+             | IDENT PATH INT      { $$ = new ast::AttachPoint($1, $2.substr(1, $2.size()-2), $3); }
              ;
 
 wildcard : wildcard IDENT { $$ = $1 + $2; }

src/semantic_analyser.cpp

@@ -339,6 +339,19 @@ void SemanticAnalyser::visit(AttachPoint &ap)
     if (ap.target == "" || ap.func == "")
       err_ << "tracepoint probe must have a target" << std::endl;
   }
+  else if (ap.provider == "profile") {
+    if (ap.target == "")
+      err_ << "profile probe must have unit of time" << std::endl;
+    else if (ap.target != "hz" &&
+             ap.target != "us" &&
+             ap.target != "ms" &&
+             ap.target != "s")
+      err_ << ap.target << " is not an accepted unit of time" << std::endl;
+    if (ap.func != "")
+      err_ << "profile probe must have an integer frequency" << std::endl;
+    else if (ap.freq <= 0)
+      err_ << "profile frequency should be a positive integer" << std::endl;
+  }
   else if (ap.provider == "BEGIN" || ap.provider == "END") {
     if (ap.target != "" || ap.func != "")
       err_ << "BEGIN/END probes should not have a target" << std::endl;

src/types.cpp

@@ -54,7 +54,9 @@ ProbeType probetype(const std::string &type)
     return ProbeType::uprobe;
   else if (type == "tracepoint")
     return ProbeType::tracepoint;
-  return ProbeType::invalid;
+  else if (type == "profile")
+    return ProbeType::profile;
+  abort();
 }
 
 } // namespace bpftrace

src/types.h

@@ -48,6 +48,7 @@ enum class ProbeType
   uprobe,
   uretprobe,
   tracepoint,
+  profile,
 };
 
 std::string typestr(Type t);
@@ -61,6 +62,7 @@ public:
   std::string attach_point;
   std::string prog_name;
   std::string name;
+  int freq;
 };
 
 } // namespace bpftrace

tests/bpftrace.cpp

@@ -51,6 +51,14 @@ void check_tracepoint(Probe &p, const std::string &target, const std::string &fu
   EXPECT_EQ("tracepoint:" + target + ":" + func, p.name);
 }
 
+void check_profile(Probe &p, const std::string &unit, int freq, const std::string &prog_name)
+{
+  EXPECT_EQ(ProbeType::profile, p.type);
+  EXPECT_EQ(freq, p.freq);
+  EXPECT_EQ(prog_name, p.prog_name);
+  EXPECT_EQ("profile:" + unit + ":" + std::to_string(freq), p.name);
+}
+
 void check_special_probe(Probe &p, const std::string &attach_point, const std::string &prog_name)
 {
   EXPECT_EQ(ProbeType::uprobe, p.type);
@@ -259,6 +267,22 @@ TEST(bpftrace, add_probes_tracepoint_wildcard_no_matches)
   EXPECT_EQ(0, bpftrace.get_special_probes().size());
 }
 
+TEST(bpftrace, add_probes_profile)
+{
+  ast::AttachPoint a("profile", "ms", 997);
+  ast::AttachPointList attach_points = { &a };
+  ast::Probe probe(&attach_points, nullptr, nullptr);
+
+  StrictMock<MockBPFtrace> bpftrace;
+
+  EXPECT_EQ(0, bpftrace.add_probe(probe));
+  EXPECT_EQ(1, bpftrace.get_probes().size());
+  EXPECT_EQ(0, bpftrace.get_special_probes().size());
+
+  std::string probe_prog_name = "profile:ms:997";
+  check_profile(bpftrace.get_probes().at(0), "ms", 997, probe_prog_name);
+}
+
 std::pair<std::vector<uint8_t>, std::vector<uint8_t>> key_value_pair_int(std::vector<uint64_t> key, int val)
 {
   std::pair<std::vector<uint8_t>, std::vector<uint8_t>> pair;

tests/parser.cpp

@@ -220,6 +220,22 @@ TEST(Parser, begin_probe)
       "  int: 1\n");
 }
 
+TEST(Parser, tracepoint_probe)
+{
+  test("tracepoint:sched:sched_switch { 1 }",
+      "Program\n"
+      " tracepoint:sched:sched_switch\n"
+      "  int: 1\n");
+}
+
+TEST(Parser, profile_probe)
+{
+  test("profile:ms:997 { 1 }",
+      "Program\n"
+      " profile:ms:997\n"
+      "  int: 1\n");
+}
+
 TEST(Parser, multiple_attach_points_kprobe)
 {
   test("BEGIN,kprobe:sys_open,uprobe:/bin/sh:foo,tracepoint:syscalls:sys_enter_* { 1 }",

tests/semantic_analyser.cpp

@@ -229,6 +229,18 @@ TEST(semantic_analyser, tracepoint)
   test("tracepoint { 1 }", 1);
 }
 
+TEST(semantic_analyser, profile)
+{
+  test("profile:hz:997 { 1 }", 0);
+  test("profile:s:10 { 1 }", 0);
+  test("profile:ms:100 { 1 }", 0);
+  test("profile:us:100 { 1 }", 0);
+  test("profile:ms:nan { 1 }", 1);
+  test("profile:unit:100 { 1 }", 1);
+  test("profile:f { 1 }", 1);
+  test("profile { 1 }", 1);
+}
+
 } // namespace semantic_analyser
 } // namespace test
 } // namespace bpftrace