From a3ae45ebe1b3576428f5eb27347704b2d099eab0 Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Mon, 6 Dec 2021 16:05:55 -0500 Subject: [PATCH] runtime/pprof: consume tag for first CPU record profBuf.write uses an index in b.tags for each entry, even if that entry has no tag (that slice entry just remains 0). profBuf.read similarly returns a tags slice with exactly as many entries as there are records in data. profileBuilder.addCPUData iterates through the tags in lockstep with the data records. Except in the special case of the first record, where it forgets to increment tags. Thus the first read of profiling data has all tags off-by-one. To help avoid regressions, addCPUData is changed to assert that tags contains exactly the correct number of tags. For #50007. Change-Id: I5f32f93003297be8d6e33ad472c185d924a63256 Reviewed-on: https://go-review.googlesource.com/c/go/+/369741 Reviewed-by: Austin Clements Trust: Michael Pratt Run-TryBot: Michael Pratt TryBot-Result: Gopher Robot --- src/runtime/cpuprof.go | 2 ++ src/runtime/pprof/pprof_test.go | 12 +++++++++++- src/runtime/pprof/proto.go | 22 +++++++++++++++------- src/runtime/pprof/proto_test.go | 14 +++++++++----- 4 files changed, 37 insertions(+), 13 deletions(-) diff --git a/src/runtime/cpuprof.go b/src/runtime/cpuprof.go index 6076564716..48cef46fe9 100644 --- a/src/runtime/cpuprof.go +++ b/src/runtime/cpuprof.go @@ -200,6 +200,8 @@ func runtime_pprof_runtime_cyclesPerSecond() int64 { // If profiling is turned off and all the profile data accumulated while it was // on has been returned, readProfile returns eof=true. // The caller must save the returned data and tags before calling readProfile again. +// The returned data contains a whole number of records, and tags contains +// exactly one entry per record. // //go:linkname runtime_pprof_readProfile runtime/pprof.readProfile func runtime_pprof_readProfile() ([]uint64, []unsafe.Pointer, bool) { diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go index e32928b347..913f899593 100644 --- a/src/runtime/pprof/pprof_test.go +++ b/src/runtime/pprof/pprof_test.go @@ -1608,6 +1608,7 @@ func TestTryAdd(t *testing.T) { testCases := []struct { name string input []uint64 // following the input format assumed by profileBuilder.addCPUData. + count int // number of records in input. wantLocs [][]string // ordered location entries with function names. wantSamples []*profile.Sample // ordered samples, we care only about Value and the profile location IDs. }{{ @@ -1617,6 +1618,7 @@ func TestTryAdd(t *testing.T) { 3, 0, 500, // hz = 500. Must match the period. 5, 0, 50, inlinedCallerStack[0], inlinedCallerStack[1], }, + count: 2, wantLocs: [][]string{ {"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}, }, @@ -1633,6 +1635,7 @@ func TestTryAdd(t *testing.T) { 7, 0, 10, inlinedCallerStack[0], inlinedCallerStack[1], inlinedCallerStack[0], inlinedCallerStack[1], 5, 0, 20, inlinedCallerStack[0], inlinedCallerStack[1], }, + count: 3, wantLocs: [][]string{{"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}}, wantSamples: []*profile.Sample{ {Value: []int64{10, 10 * period}, Location: []*profile.Location{{ID: 1}, {ID: 1}}}, @@ -1646,6 +1649,7 @@ func TestTryAdd(t *testing.T) { // entry. The "stk" entry is actually the count. 4, 0, 0, 4242, }, + count: 2, wantLocs: [][]string{{"runtime/pprof.lostProfileEvent"}}, wantSamples: []*profile.Sample{ {Value: []int64{4242, 4242 * period}, Location: []*profile.Location{{ID: 1}}}, @@ -1664,6 +1668,7 @@ func TestTryAdd(t *testing.T) { 5, 0, 30, inlinedCallerStack[0], inlinedCallerStack[0], 4, 0, 40, inlinedCallerStack[0], }, + count: 3, // inlinedCallerDump shows up here because // runtime_expandFinalInlineFrame adds it to the stack frame. wantLocs: [][]string{{"runtime/pprof.inlinedCalleeDump"}, {"runtime/pprof.inlinedCallerDump"}}, @@ -1677,6 +1682,7 @@ func TestTryAdd(t *testing.T) { 3, 0, 500, // hz = 500. Must match the period. 9, 0, 10, recursionStack[0], recursionStack[1], recursionStack[2], recursionStack[3], recursionStack[4], recursionStack[5], }, + count: 2, wantLocs: [][]string{ {"runtime/pprof.recursionChainBottom"}, { @@ -1700,6 +1706,7 @@ func TestTryAdd(t *testing.T) { 5, 0, 50, inlinedCallerStack[0], inlinedCallerStack[1], 4, 0, 60, inlinedCallerStack[0], }, + count: 3, wantLocs: [][]string{{"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}}, wantSamples: []*profile.Sample{ {Value: []int64{50, 50 * period}, Location: []*profile.Location{{ID: 1}}}, @@ -1712,6 +1719,7 @@ func TestTryAdd(t *testing.T) { 4, 0, 70, inlinedCallerStack[0], 5, 0, 80, inlinedCallerStack[0], inlinedCallerStack[1], }, + count: 3, wantLocs: [][]string{{"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}}, wantSamples: []*profile.Sample{ {Value: []int64{70, 70 * period}, Location: []*profile.Location{{ID: 1}}}, @@ -1724,6 +1732,7 @@ func TestTryAdd(t *testing.T) { 3, 0, 500, // hz = 500. Must match the period. 4, 0, 70, inlinedCallerStack[0], }, + count: 2, wantLocs: [][]string{{"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}}, wantSamples: []*profile.Sample{ {Value: []int64{70, 70 * period}, Location: []*profile.Location{{ID: 1}}}, @@ -1739,6 +1748,7 @@ func TestTryAdd(t *testing.T) { // from getting merged into above. 5, 0, 80, inlinedCallerStack[1], inlinedCallerStack[0], }, + count: 3, wantLocs: [][]string{ {"runtime/pprof.inlinedCalleeDump", "runtime/pprof.inlinedCallerDump"}, {"runtime/pprof.inlinedCallerDump"}, @@ -1751,7 +1761,7 @@ func TestTryAdd(t *testing.T) { for _, tc := range testCases { t.Run(tc.name, func(t *testing.T) { - p, err := translateCPUProfile(tc.input) + p, err := translateCPUProfile(tc.input, tc.count) if err != nil { t.Fatalf("translating profile: %v", err) } diff --git a/src/runtime/pprof/proto.go b/src/runtime/pprof/proto.go index 54e7a80183..073a076802 100644 --- a/src/runtime/pprof/proto.go +++ b/src/runtime/pprof/proto.go @@ -266,8 +266,9 @@ func newProfileBuilder(w io.Writer) *profileBuilder { } // addCPUData adds the CPU profiling data to the profile. -// The data must be a whole number of records, -// as delivered by the runtime. +// +// The data must be a whole number of records, as delivered by the runtime. +// len(tags) must be equal to the number of records in data. func (b *profileBuilder) addCPUData(data []uint64, tags []unsafe.Pointer) error { if !b.havePeriod { // first record is period @@ -282,6 +283,9 @@ func (b *profileBuilder) addCPUData(data []uint64, tags []unsafe.Pointer) error b.period = 1e9 / int64(data[2]) b.havePeriod = true data = data[3:] + // Consume tag slot. Note that there isn't a meaningful tag + // value for this record. + tags = tags[1:] } // Parse CPU samples from the profile. @@ -306,14 +310,14 @@ func (b *profileBuilder) addCPUData(data []uint64, tags []unsafe.Pointer) error if data[0] < 3 || tags != nil && len(tags) < 1 { return fmt.Errorf("malformed profile") } + if len(tags) < 1 { + return fmt.Errorf("mismatched profile records and tags") + } count := data[2] stk := data[3:data[0]] data = data[data[0]:] - var tag unsafe.Pointer - if tags != nil { - tag = tags[0] - tags = tags[1:] - } + tag := tags[0] + tags = tags[1:] if count == 0 && len(stk) == 1 { // overflow record @@ -327,6 +331,10 @@ func (b *profileBuilder) addCPUData(data []uint64, tags []unsafe.Pointer) error } b.m.lookup(stk, tag).count += int64(count) } + + if len(tags) != 0 { + return fmt.Errorf("mismatched profile records and tags") + } return nil } diff --git a/src/runtime/pprof/proto_test.go b/src/runtime/pprof/proto_test.go index 4a9749a83f..ea0ed9aefd 100644 --- a/src/runtime/pprof/proto_test.go +++ b/src/runtime/pprof/proto_test.go @@ -17,16 +17,20 @@ import ( "runtime" "strings" "testing" + "unsafe" ) // translateCPUProfile parses binary CPU profiling stack trace data // generated by runtime.CPUProfile() into a profile struct. // This is only used for testing. Real conversions stream the // data into the profileBuilder as it becomes available. -func translateCPUProfile(data []uint64) (*profile.Profile, error) { +// +// count is the number of records in data. +func translateCPUProfile(data []uint64, count int) (*profile.Profile, error) { var buf bytes.Buffer b := newProfileBuilder(&buf) - if err := b.addCPUData(data, nil); err != nil { + tags := make([]unsafe.Pointer, count) + if err := b.addCPUData(data, tags); err != nil { return nil, err } b.build() @@ -46,7 +50,7 @@ func TestConvertCPUProfileEmpty(t *testing.T) { var buf bytes.Buffer b := []uint64{3, 0, 500} // empty profile at 500 Hz (2ms sample period) - p, err := translateCPUProfile(b) + p, err := translateCPUProfile(b, 1) if err != nil { t.Fatalf("translateCPUProfile: %v", err) } @@ -120,7 +124,7 @@ func TestConvertCPUProfile(t *testing.T) { 5, 0, 40, uint64(addr2 + 1), uint64(addr2 + 2), // 40 samples in addr2 5, 0, 10, uint64(addr1 + 1), uint64(addr1 + 2), // 10 samples in addr1 } - p, err := translateCPUProfile(b) + p, err := translateCPUProfile(b, 4) if err != nil { t.Fatalf("translating profile: %v", err) } @@ -429,7 +433,7 @@ func TestEmptyStack(t *testing.T) { 3, 0, 500, // hz = 500 3, 0, 10, // 10 samples with an empty stack trace } - _, err := translateCPUProfile(b) + _, err := translateCPUProfile(b, 2) if err != nil { t.Fatalf("translating profile: %v", err) }