cooker, seitan: simple working example

parser:
  - add OP_BLOCK and OP_RETURN to the parser
seitan:
  - fix op_cmp in seitan, it was jmp when comparison was true

Working example:
demo.json:
[
  {
    "match": [ /* qemu-pr-helper and similar */
      { "connect": { "addr": { "family": "unix", "path": "/tmp/test.sock" } } }
    ],
    "return": 0
  }
]

Create gluten and the bpf filter:
$ seitan-cooker demo.hjson demo.gluten demo.bpf

Launch the seitan eater with the target program:
$ seitan-eater -i demo.bpf -- strace -e connect tests-utils/test-syscalls connect

Start seitan with gluten:
$ seitan -i demo.gluten -p $(pgrep seitan-eater)

Seitan mocks the connect syscall and `connect` returns successfully:
$ seitan-eater -i demo.bpf -- strace -e connect tests-utils/test-syscalls connect
Test syscall: connect
connect(4, {sa_family=AF_UNIX, sun_path="/tmp/test.sock"}, 108) = 0

1 files changed, 2 insertions, 0 deletions

diff --git a/cooker/emit.h b/cooker/emit.h
index 2135052..5d15b1b 100644
--- a/cooker/emit.h
+++ b/cooker/emit.h
@@ -16,6 +16,8 @@ void emit_cmp_field(struct gluten_ctx *g, enum op_cmp_type cmp,
 		    struct field *field,
 		    struct gluten_offset base, struct gluten_offset match,
 		    enum jump_type jmp);
+void emit_return(struct gluten_ctx *g, struct gluten_offset v);
+void emit_block(struct gluten_ctx *g, int32_t error);
 struct gluten_offset emit_data(struct gluten_ctx *g, enum type type,
 			       size_t str_len, union value *value);
 void link_block(struct gluten_ctx *g);