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, 5 insertions, 0 deletions

diff --git a/runsc/cmd/boot.go b/runsc/cmd/boot.go
index d26e92bcd..023b63dc0 100644
--- a/runsc/cmd/boot.go
+++ b/runsc/cmd/boot.go
@@ -66,6 +66,9 @@ type Boot struct {
 	// totalMem sets the initial amount of total memory to report back to the
 	// container.
 	totalMem uint64
+
+	// userLogFD is the file descriptor to write user logs to.
+	userLogFD int
 }
 
 // Name implements subcommands.Command.Name.
@@ -95,6 +98,7 @@ func (b *Boot) SetFlags(f *flag.FlagSet) {
 	f.BoolVar(&b.applyCaps, "apply-caps", false, "if true, apply capabilities defined in the spec to the process")
 	f.IntVar(&b.cpuNum, "cpu-num", 0, "number of CPUs to create inside the sandbox")
 	f.Uint64Var(&b.totalMem, "total-memory", 0, "sets the initial amount of total memory to report back to the container")
+	f.IntVar(&b.userLogFD, "user-log-fd", 0, "file descriptor to write user logs to. 0 means no logging.")
 }
 
 // Execute implements subcommands.Command.Execute.  It starts a sandbox in a
@@ -163,6 +167,7 @@ func (b *Boot) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
 		Console:      b.console,
 		NumCPU:       b.cpuNum,
 		TotalMem:     b.totalMem,
+		UserLogFD:    b.userLogFD,
 	}
 	l, err := boot.New(bootArgs)
 	if err != nil {