gmon requires target binary to be built with go1.23+

README.md

@@ -8,6 +8,7 @@
 
 - amd64 (x86_64)
 - Linux Kernel 5.8+ since `gmon` uses [BPF ring buffer](https://nakryiko.com/posts/bpf-ringbuf/)
+- Target Go binary must be compiled with Go 1.23+ since `gmon` uses fixed offset to get goroutine ID
 
 # Usage
 

ebpf/c/gmon.c

@@ -24,9 +24,9 @@ int runtime_newproc1(struct pt_regs *ctx) {
  bpf_printk("%s:%d | failed to extract new goroutine pointer from retval\n", __FILE__, __LINE__);
  return 0;
  }
- // `pahole -C runtime.g /path/to/gobinary 2>/dev/null` shows the offsets of the goid which is 152.
+ // `pahole -C runtime.g /path/to/gobinary 2>/dev/null` shows the offsets of the goid.
  int64_t goid = 0;
- if (bpf_core_read_user(&goid, sizeof(int64_t), newg_p + 152)) {
+ if (bpf_core_read_user(&goid, sizeof(int64_t), newg_p + 160)) {
  bpf_printk("%s:%d | failed to read goroutine id from newg with the offset\n", __FILE__, __LINE__);
  return 0;
  }

ebpf/c/goroutine.h

@@ -18,7 +18,7 @@ struct gobuf_t {
  uintptr_t bp;
 };
 
-// https://github.com/golang/go/blob/release-branch.go1.21/src/runtime/runtime2.go#L447
+// https://github.com/golang/go/blob/release-branch.go1.23/src/runtime/runtime2.go#L458
 struct g_t {
  struct stack_t stack_instance;
  uintptr_t stackguard0;
@@ -29,6 +29,7 @@ struct g_t {
  struct gobuf_t sched;
  uintptr_t syscallsp;
  uintptr_t syscallpc;
+ uintptr_t syscallbp;
  uintptr_t stktopsp;
  uintptr_t param;
  uint32_t atomicstatus;

fixture/go.mod

@@ -1,3 +1,3 @@
 module fixture
 
-go 1.22.1
+go 1.23.1

gmon.sh

@@ -43,7 +43,7 @@ ln -s /usr/bin/llvm-strip-14 /usr/bin/llvm-strip
 ln -s /usr/bin/clang-14 /usr/bin/clang
 ln -s /usr/bin/clang-format-14 /usr/bin/clang-format
 wget -O- --no-check-certificate https://github.com/libbpf/bpftool/releases/download/v7.3.0/bpftool-v7.3.0-amd64.tar.gz | tar -xzf - -C /usr/bin && chmod +x /usr/bin/bpftool
-wget -O- --no-check-certificate https://go.dev/dl/go1.22.3.linux-amd64.tar.gz | tar -xzf - -C /usr/local && chmod +x /usr/local/go/bin/go && ln -s /usr/local/go/bin/go /usr/bin/go
+wget -O- --no-check-certificate https://go.dev/dl/go1.23.1.linux-amd64.tar.gz | tar -xzf - -C /usr/local && chmod +x /usr/local/go/bin/go && ln -s /usr/local/go/bin/go /usr/bin/go
 END
 WORKDIR /usr/src
 COPY go.mod go.mod

go.mod

@@ -1,6 +1,6 @@
 module github.com/keisku/gmon
 
-go 1.22.3
+go 1.23.1
 
 require (
  github.com/cilium/ebpf v0.15.0

main.go

@@ -3,6 +3,7 @@ package main
 import (
  "bufio"
  "context"
+ "debug/buildinfo"
  "errors"
  "flag"
  "fmt"
@@ -16,6 +17,7 @@ import (
  "runtime"
  "runtime/debug"
  "runtime/trace"
+ "strconv"
  "strings"
 
  "github.com/cilium/ebpf/rlimit"
@@ -87,6 +89,14 @@ func main() {
  errlog.Fatalln("gmon only works on amd64 Linux")
  }
 
+ binfo, err := buildinfo.ReadFile(*binPath)
+ if err != nil {
+ errlog.Fatalln(err)
+ }
+ if !isGoVersion123OrHigher(binfo.GoVersion) {
+ errlog.Fatalf("gmon requires Go 1.23 or higher, but %s is used for %s", binfo.GoVersion, binfo.Main.Path)
+ }
+
  if *traceOutPath != "" {
  traceOutFile, err := os.Create(*traceOutPath)
  if err != nil {
@@ -161,3 +171,21 @@ func logTracePipe(done <-chan struct{}) {
  }()
  <-done
 }
+
+func isGoVersion123OrHigher(v string) bool {
+ versionSplit := strings.Split(v, ".")
+ if len(versionSplit) != 3 {
+ return false
+ }
+ if versionSplit[0] != "go1" {
+ return false
+ }
+ minor, err := strconv.Atoi(versionSplit[1])
+ if err != nil {
+ return false
+ }
+ if minor < 23 {
+ return false
+ }
+ return true
+}