Add bare bones unsupported syscall logging

This change introduces a new flags to create/run called
--user-log. Logs to this files are visible to users and
are meant to help debugging problems with their images
and containers.

For now only unsupported syscalls are sent to this log,
and only minimum support was added. We can build more
infrastructure around it as needed.

PiperOrigin-RevId: 216735977
Change-Id: I54427ca194604991c407d49943ab3680470de2d0

1 files changed, 36 insertions, 0 deletions

diff --git a/runsc/container/test_app.go b/runsc/container/test_app.go
index f69cfdf83..9e4b5326d 100644
--- a/runsc/container/test_app.go
+++ b/runsc/container/test_app.go
@@ -24,6 +24,7 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
+	sys "syscall"
 	"time"
 
 	"flag"
@@ -38,6 +39,7 @@ func main() {
 	subcommands.Register(new(taskTree), "")
 	subcommands.Register(new(forkBomb), "")
 	subcommands.Register(new(reaper), "")
+	subcommands.Register(new(syscall), "")
 
 	flag.Parse()
 
@@ -241,3 +243,37 @@ func (c *reaper) Execute(ctx context.Context, f *flag.FlagSet, args ...interface
 	defer stop()
 	select {}
 }
+
+type syscall struct {
+	sysno uint64
+}
+
+// Name implements subcommands.Command.
+func (*syscall) Name() string {
+	return "syscall"
+}
+
+// Synopsis implements subcommands.Command.
+func (*syscall) Synopsis() string {
+	return "syscall makes a syscall"
+}
+
+// Usage implements subcommands.Command.
+func (*syscall) Usage() string {
+	return "syscall <flags>"
+}
+
+// SetFlags implements subcommands.Command.
+func (s *syscall) SetFlags(f *flag.FlagSet) {
+	f.Uint64Var(&s.sysno, "syscall", 0, "syscall to call")
+}
+
+// Execute implements subcommands.Command.
+func (s *syscall) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if _, _, errno := sys.Syscall(uintptr(s.sysno), 0, 0, 0); errno != 0 {
+		fmt.Printf("syscall(%d, 0, 0...) failed: %v\n", s.sysno, errno)
+	} else {
+		fmt.Printf("syscall(%d, 0, 0...) success\n", s.sysno)
+	}
+	return subcommands.ExitSuccess
+}