golang.org/x/tools@v0.21.0/go/analysis/passes/framepointer/framepointer.go (about) 1 // Copyright 2020 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package framepointer defines an Analyzer that reports assembly code 6 // that clobbers the frame pointer before saving it. 7 package framepointer 8 9 import ( 10 "go/build" 11 "regexp" 12 "strings" 13 14 "golang.org/x/tools/go/analysis" 15 "golang.org/x/tools/go/analysis/passes/internal/analysisutil" 16 ) 17 18 const Doc = "report assembly that clobbers the frame pointer before saving it" 19 20 var Analyzer = &analysis.Analyzer{ 21 Name: "framepointer", 22 Doc: Doc, 23 URL: "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/framepointer", 24 Run: run, 25 } 26 27 var ( 28 re = regexp.MustCompile 29 asmWriteBP = re(`,\s*BP$`) // TODO: can have false positive, e.g. for TESTQ BP,BP. Seems unlikely. 30 asmMentionBP = re(`\bBP\b`) 31 asmControlFlow = re(`^(J|RET)`) 32 ) 33 34 func run(pass *analysis.Pass) (interface{}, error) { 35 if build.Default.GOARCH != "amd64" { // TODO: arm64 also? 36 return nil, nil 37 } 38 if build.Default.GOOS != "linux" && build.Default.GOOS != "darwin" { 39 return nil, nil 40 } 41 42 // Find assembly files to work on. 43 var sfiles []string 44 for _, fname := range pass.OtherFiles { 45 if strings.HasSuffix(fname, ".s") && pass.Pkg.Path() != "runtime" { 46 sfiles = append(sfiles, fname) 47 } 48 } 49 50 for _, fname := range sfiles { 51 content, tf, err := analysisutil.ReadFile(pass, fname) 52 if err != nil { 53 return nil, err 54 } 55 56 lines := strings.SplitAfter(string(content), "\n") 57 active := false 58 for lineno, line := range lines { 59 lineno++ 60 61 // Ignore comments and commented-out code. 62 if i := strings.Index(line, "//"); i >= 0 { 63 line = line[:i] 64 } 65 line = strings.TrimSpace(line) 66 67 // We start checking code at a TEXT line for a frameless function. 68 if strings.HasPrefix(line, "TEXT") && strings.Contains(line, "(SB)") && strings.Contains(line, "$0") { 69 active = true 70 continue 71 } 72 if !active { 73 continue 74 } 75 76 if asmWriteBP.MatchString(line) { // clobber of BP, function is not OK 77 pass.Reportf(analysisutil.LineStart(tf, lineno), "frame pointer is clobbered before saving") 78 active = false 79 continue 80 } 81 if asmMentionBP.MatchString(line) { // any other use of BP might be a read, so function is OK 82 active = false 83 continue 84 } 85 if asmControlFlow.MatchString(line) { // give up after any branch instruction 86 active = false 87 continue 88 } 89 } 90 } 91 return nil, nil 92 }