3 Commits (literalRecheck)

Author	SHA1	Message	Date
Daniel Martí	79376a15f9	support computing missing pkgCache entries ... Some users had been running into "cannot load cache entry" errors, which could happen if garble's cache files in GOCACHE were removed when Go's own cache files were not. Now that we've moved to our own separate cache directory, and that we've refactored the codebase to depend less on globals and no longer assume that we're loading info for the current package, we can now compute a pkgCache entry for a dependency if needed. We add a pkgCache.CopyFrom method to be able to append map entries from one pkgCache to another without needing an encoding/gob roundtrip. We also add a parseFiles helper, since we now have three bits of code which need to parse a list of Go files from disk. Fixes #708.	2 years ago
Daniel Martí	7d1bd13778	replace our caching inside GOCACHE with GARBLE_CACHE ... For each Go package we obfuscate, we need to store information about how we obfuscated it, which is needed when obfuscating its dependents. For example, if A depends on B to use the type B.Foo, A needs to know whether or not B.Foo was obfuscated; it depends on B's use of reflect. We record this information in a gob file, which is cached on disk. To avoid rolling our own custom cache, and since garble is so closely connected with cmd/go already, we piggybacked off of Go's GOCACHE. In particular, for each build cache entry per `go list`'s Export field, we would store a "garble" sibling file with that gob content. However, this was brittle for two reasons: 1) We were doing this without cmd/go's permission or knowledge. We were careful to use filename suffixes similar to Export files, meaning that `go clean` and other commands would treat them the same. However, this could confuse cmd/go at any point in the future. 2) cmd/go trims cache entries in GOCACHE regularly, to keep the size of the build and test caches under control. Right now, this means that every 24h, any file not accessed in the last five days is deleted. However, that trimming heuristic is done per-file. If the trimming removed Garble's sibling file but not the original Export file, this could cause errors such as "cannot load garble export file" which users already ran into. Instead, start using github.com/rogpeppe/go-internal/cache, an exported copy of cmd/go's own cache implementation for GOCACHE. Since we need an entirely separate directory, we introduce GARBLE_CACHE, defaulting to the "garble" directory inside the user's cache directory. For example, on Linux this would be ~/.cache/garble. Inside GARBLE_CACHE, our gob file cache will be under "build", which helps clarify that this cache is used when obfuscating Go builds, and allows placing other kinds of caches inside GARBLE_CACHE. For example, we already have a need for storing linker binaries, which for now still use their own caching mechanism. This commit does not make our cache properly resistant to removed files. The proof is that our seed.txtar testscript still fails the second case. However, we do rewrite all of our caching logic away from Export files, which in itself is a considerable refactor, and we add a few TODOs. One notable change is how we load gob files from dependencies when building the cache entry for the current package. We used to load the gob files from all packages in the Deps field. However, that is the list of all _transitive_ dependencies. Since these gob files are already flat, meaning they contain information about all of their transitive dependencies as well, we need only load the gob files from the direct dependencies, the Imports field. Performance is largely unchanged, since the behavior is similar. However, the change from Deps to Imports saves us some work, which can be seen in the reduced mallocs per obfuscated build. It's unclear why the binary size isn't stable. When reverting the Deps to Imports change, it then settles at 5.386Mi, which is almost exactly in between the two measurements below. I'm not sure why, but that metric appears to be slightly unstable. goos: linux goarch: amd64 pkg: mvdan.cc/garble cpu: AMD Ryzen 7 PRO 5850U with Radeon Graphics │ old │ new │ │ sec/op │ sec/op vs base │ Build-8 11.09 ± 1% 11.08 ± 1% ~ (p=0.796 n=10) │ old │ new │ │ bin-B │ bin-B vs base │ Build-8 5.390Mi ± 0% 5.382Mi ± 0% -0.14% (p=0.000 n=10) │ old │ new │ │ cached-sec/op │ cached-sec/op vs base │ Build-8 415.5m ± 4% 421.6m ± 1% ~ (p=0.190 n=10) │ old │ new │ │ mallocs/op │ mallocs/op vs base │ Build-8 35.43M ± 0% 34.05M ± 0% -3.89% (p=0.000 n=10) │ old │ new │ │ sys-sec/op │ sys-sec/op vs base │ Build-8 5.662 ± 1% 5.701 ± 2% ~ (p=0.280 n=10)	2 years ago
Daniel Martí	9044b1d31c	add a test to reproduce our caching bugs ... The test passes, because it expects garble to fail the same way that users are seeing in practice. For #708.	2 years ago