internal/pkg: implement exec artifact

This runs a program in a container environment. Artifacts can be made available to the container, they are cured concurrently and mounted in order.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/testdata/main.go

@@ -0,0 +1,103 @@
+//go:build testtool
+
+package main
+
+import (
+	"log"
+	"os"
+	"path"
+	"slices"
+
+	"hakurei.app/container/fhs"
+	"hakurei.app/container/vfs"
+)
+
+func main() {
+	log.SetFlags(0)
+	log.SetPrefix("testtool: ")
+
+	if wantArgs := []string{"testtool"}; !slices.Equal(os.Args, wantArgs) {
+		log.Fatalf("Args: %q, want %q", os.Args, wantArgs)
+	}
+	if wantEnv := []string{
+		"HAKUREI_TEST=1",
+	}; !slices.Equal(wantEnv, os.Environ()) {
+		log.Fatalf("Environ: %q, want %q", os.Environ(), wantEnv)
+	}
+	const wantExec = "/opt/bin/testtool"
+	if got, err := os.Executable(); err != nil {
+		log.Fatalf("Executable: error = %v", err)
+	} else if got != wantExec {
+		log.Fatalf("Executable: %q, want %q", got, wantExec)
+	}
+
+	var m *vfs.MountInfo
+	if f, err := os.Open(fhs.Proc + "self/mountinfo"); err != nil {
+		log.Fatalf("Open: error = %v", err)
+	} else {
+		err = vfs.NewMountInfoDecoder(f).Decode(&m)
+		closeErr := f.Close()
+		if err != nil {
+			log.Fatalf("Decode: error = %v", err)
+		}
+		if closeErr != nil {
+			log.Fatalf("Close: error = %v", err)
+		}
+	}
+
+	log.Println(m)
+	if m.Root != "/sysroot" || m.Target != "/" {
+		log.Fatal("unexpected root mount entry")
+	}
+	next := func() { m = m.Next; log.Println(m) }
+
+	next()
+	if path.Base(m.Root) != "OLBgp1GsljhM2TJ-sbHjaiH9txEUvgdDTAzHv2P24donTt6_529l-9Ua0vFImLlb" {
+		log.Fatal("unexpected file artifact checksum")
+	}
+
+	next()
+	if path.Base(m.Root) != "MGWmEfjut2QE2xPJwTsmUzpff4BN_FEnQ7T0j7gvUCCiugJQNwqt9m151fm9D1yU" {
+		log.Fatal("unexpected artifact checksum")
+	}
+
+	next() // testtool artifact
+
+	next()
+	if path.Base(m.Root) !=
+		"oHuqV7p0v1Vd8IdAzjyYM8sfCS0P2LR5tfv5cb6Gbf2ZWUm8Ec-7hYPJ_qr183m7" || m.Target != "/work" {
+		log.Fatal("unexpected work mount entry")
+	}
+
+	next()
+	if path.Base(m.Root) !=
+		"oHuqV7p0v1Vd8IdAzjyYM8sfCS0P2LR5tfv5cb6Gbf2ZWUm8Ec-7hYPJ_qr183m7" || m.Target != "/tmp" {
+		log.Fatal("unexpected temp mount entry")
+	}
+
+	next()
+	if m.Root != "/" || m.Target != "/proc" || m.Source != "proc" || m.FsType != "proc" {
+		log.Fatal("unexpected proc mount entry")
+	}
+
+	next()
+	if m.Root != "/" || m.Target != "/dev" || m.Source != "devtmpfs" || m.FsType != "tmpfs" {
+		log.Fatal("unexpected dev mount entry")
+	}
+
+	for i := 0; i < 9; i++ { // private /dev entries
+		next()
+	}
+
+	if m.Next != nil {
+		log.Println("unexpected extra mount entries")
+		for m.Next != nil {
+			next()
+		}
+		os.Exit(1)
+	}
+
+	if err := os.WriteFile("check", []byte{0}, 0400); err != nil {
+		log.Fatal(err)
+	}
+}