runsc: Terminal support for "docker exec -ti".

This CL adds terminal support for "docker exec".  We previously only supported
consoles for the container process, but not exec processes.

The SYS_IOCTL syscall was added to the default seccomp filter list, but only
for ioctls that get/set winsize and termios structs. We need to allow these
ioctl for all containers because it's possible to run "exec -ti" on a
container that was started without an attached console, after the filters
have been installed.

Note that control-character signals are still not properly supported.

Tested with:
	$ docker run --runtime=runsc -it alpine
In another terminial:
	$ docker exec -it <containerid> /bin/sh

PiperOrigin-RevId: 210185456
Change-Id: I6d2401e53a7697bb988c120a8961505c335f96d9

1 files changed, 16 insertions, 0 deletions

diff --git a/runsc/console/BUILD b/runsc/console/BUILD
new file mode 100644
index 000000000..fa1a7d430
--- /dev/null
+++ b/runsc/console/BUILD
@@ -0,0 +1,16 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "console",
+    srcs = ["console.go"],
+    importpath = "gvisor.googlesource.com/gvisor/runsc/console",
+    visibility = [
+        "//runsc:__subpackages__",
+    ],
+    deps = [
+        "@com_github_kr_pty//:go_default_library",
+        "@org_golang_x_sys//unix:go_default_library",
+    ],
+)