ebpf-challenge/GetRuntimeAddresses/symbolyze/gdb_test.go

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package symbolyze
import (
"bufio"
"fmt"
"os"
"os/exec"
"regexp"
"strconv"
"sync"
"testing"
)
// buildSimple calls make in the testdata-directory in order to build the
// test-binary `simple` that is linked against python3.7. If this fails, make
// necessary adjustments to the Makefile and/or your environment and try again.
func buildSimple() error {
cmd := exec.Command("make", "-s")
cmd.Dir = "testdata"
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
return cmd.Run()
}
// TestSimpeGDB runs the program testdata/simple multiple times and uses gdb to
// extract the address of the symbol _PyRuntime for each pid. It compares
// those with the results from Scanner.Run().
func TestSimpleGDB(t *testing.T) {
ourResults := map[int]uint64{}
gdbResults := map[int]uint64{}
err := buildSimple()
if err != nil {
t.Fatal(err)
}
scanner := NewScanner("_PyRuntime", "*python3*")
var m sync.Mutex
scanner.OnFound(func(pid int, offset uint64) error {
t.Logf("scanner setting pid %d to offset %x", pid, offset)
m.Lock()
ourResults[pid] = offset
m.Unlock()
return nil
})
for i := 0; i < 5; i++ {
simple := exec.Command("testdata/simple")
if err := simple.Start(); err != nil {
t.Fatal(err)
}
defer func() {
simple.Process.Kill()
simple.Wait()
}()
t.Logf("Asking Gdb about PID %d", simple.Process.Pid)
offset, err := extractOffsetWithGdb(simple.Process.Pid, t)
if err != nil {
t.Fatalf("extractOffsetWithGdb: %v", err)
}
t.Logf("Found offset at 0x%x", offset)
gdbResults[simple.Process.Pid] = offset
}
if err = scanner.Run(); err != nil {
t.Logf("Scanner failure: %v", err)
}
for pid, off := range gdbResults {
if off2, ok := ourResults[pid]; !ok {
t.Fatalf("Scanner has no offset for pid %d", pid)
} else if off != off2 {
t.Fatalf("Scanner has found offset %x while gdb has found offset %x for pid %d", off2, off, pid)
} else {
t.Logf("Scanner and gdb agree: pid %d at offset %x", pid, off)
}
}
}
// searchRX should match the output of gdb when it prints the address of the
// symbol
var searchRX = regexp.MustCompile(`Symbol "_PyRuntime" is.* at.* 0x([0-9a-fA-F]+)`)
// extractOffsetWithGdb calls gdb in batch-mode on a pid and looks up the
// address of the symbol _PyRuntime by calling `info address _PyRuntime`. If
// found, it extracts the address from the gdb-output.
func extractOffsetWithGdb(pid int, t *testing.T) (offset uint64, err error) {
cmd := exec.Command("gdb",
"--batch",
"-p", strconv.Itoa(pid),
"-ex", "info address _PyRuntime",
"-ex", "quit")
output, err := cmd.StdoutPipe()
if err != nil {
return 0, err
}
if err := cmd.Start(); err != nil {
return 0, err
}
defer cmd.Wait()
scanner := bufio.NewScanner(output)
for scanner.Scan() {
line := scanner.Text()
// t.Logf("[gdb]: %v", line)
match := searchRX.FindStringSubmatch(line)
if len(match) > 1 {
return strconv.ParseUint(match[1], 16, 64)
}
}
return 0, fmt.Errorf("Symbol not found with gdb.\n" +
"Maybe /proc/sys/kernel/yama/ptrace_scope must be set to 0? Or try to run the test as root!")
}