prog, pkg/compiler: add `BufferCompressed` buffer type & `compressed_image` builtin

Create the `BufferCompressed` kind of `BufferType`, which will be used
to represent compressed data. Create the corresponding `compressed_image`
syzlang builtin, which is backed by `BufferCompressed`. For now, no
syscalls use this feature - this will be introduced in future commits.

We have to be careful to decompress the data before mutating, and
re-compress before storing. We make sure that any deserialised
`BufferCompressed` data is valid too.

`BufferCompressed` arguments are mutated using a generic heatmap. In
future, we could add variants of `BufferCompressed` or populate the
`BufferType` sub-kind, using it to choose different kinds of heatmap for
different uncompressed data formats.

Various operations on compressed data must be forbidden, so we check for
`BufferCompressed` in key places. We also have to ensure `compressed_image`
can only be used in syscalls that are marked `no_{generate,minimize}`.
Therefore, we add a generic compiler check which allows type
descriptions to require attributes on the syscalls which use them.

1 files changed, 3 insertions, 0 deletions

diff --git a/prog/minimization.go b/prog/minimization.go
index ee8f565c9..68cca2ec4 100644
--- a/prog/minimization.go
+++ b/prog/minimization.go
@@ -301,6 +301,9 @@ func (typ *BufferType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool
 	if arg.Dir() == DirOut {
 		return false
 	}
+	if typ.IsCompressed() {
+		panic(fmt.Sprintf("minimizing `no_minimize` call %v", ctx.call.Meta.Name))
+	}
 	a := arg.(*DataArg)
 	switch typ.Kind {
 	case BufferBlobRand, BufferBlobRange: