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, 1 insertions, 1 deletions

diff --git a/prog/prio.go b/prog/prio.go
index d0013b75d..535999c1a 100644
--- a/prog/prio.go
+++ b/prog/prio.go
@@ -96,7 +96,7 @@ func (target *Target) calcResourceUsage() map[string]map[int]weights {
 			}
 		case *BufferType:
 			switch a.Kind {
-			case BufferBlobRand, BufferBlobRange, BufferText:
+			case BufferBlobRand, BufferBlobRange, BufferText, BufferCompressed:
 			case BufferString, BufferGlob:
 				if a.SubKind != "" {
 					noteUsage(uses, c, 2, ctx.Dir, fmt.Sprintf("str-%v", a.SubKind))