hst/config: handle filesystem entry targeting root

This allows any fstype supported by hst to be directly mounted on sysroot. A special case in internal/app applies the matching entry early and excludes it from path hiding.

Closes #5.

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

7 files changed, 64 insertions, 37 deletions

diff --git a/cmd/hakurei/print.go b/cmd/hakurei/print.go
index d163efc3..3e238d65 100644
--- a/cmd/hakurei/print.go
+++ b/cmd/hakurei/print.go
@@ -110,10 +110,6 @@ func printShowInstance(
 		}
 		t.Printf(" Flags:\t%s\n", strings.Join(flags, " "))
 
-		if params.AutoRoot != nil {
-			t.Printf(" Root:\t%s (%d)\n", params.AutoRoot, params.RootFlags)
-		}
-
 		etc := params.Etc
 		if etc == nil {
 			etc = container.AbsFHSEtc
diff --git a/cmd/hakurei/print_test.go b/cmd/hakurei/print_test.go
index dab4b9ec..b55c1044 100644
--- a/cmd/hakurei/print_test.go
+++ b/cmd/hakurei/print_test.go
@@ -42,12 +42,12 @@ func Test_printShowInstance(t *testing.T) {
  Data:           /var/lib/hakurei/u0/org.chromium.Chromium
  Hostname:       localhost
  Flags:          userns devel net abstract device tty mapuid autoetc
- Root:           /var/lib/hakurei/base/org.debian (2)
  Etc:            /etc/
  Path:           /run/current-system/sw/bin/chromium
  Arguments:      chromium --ignore-gpu-blocklist --disable-smooth-scrolling --enable-features=UseOzonePlatform --ozone-platform=wayland
 
 Filesystem
+ autoroot:w:/var/lib/hakurei/base/org.debian
  w+ephemeral(-rwxr-xr-x):/tmp/
  w*/nix/store:/mnt-root/nix/.rw-store/upper:/mnt-root/nix/.rw-store/work:/mnt-root/nix/.ro-store
  */nix/store
@@ -121,12 +121,12 @@ App
  Data:           /var/lib/hakurei/u0/org.chromium.Chromium
  Hostname:       localhost
  Flags:          userns devel net abstract device tty mapuid autoetc
- Root:           /var/lib/hakurei/base/org.debian (2)
  Etc:            /etc/
  Path:           /run/current-system/sw/bin/chromium
  Arguments:      chromium --ignore-gpu-blocklist --disable-smooth-scrolling --enable-features=UseOzonePlatform --ozone-platform=wayland
 
 Filesystem
+ autoroot:w:/var/lib/hakurei/base/org.debian
  w+ephemeral(-rwxr-xr-x):/tmp/
  w*/nix/store:/mnt-root/nix/.rw-store/upper:/mnt-root/nix/.rw-store/work:/mnt-root/nix/.ro-store
  */nix/store
@@ -280,6 +280,13 @@ App
       "device": true,
       "filesystem": [
         {
+          "type": "bind",
+          "dst": "/",
+          "src": "/var/lib/hakurei/base/org.debian",
+          "write": true,
+          "autoroot": true
+        },
+        {
           "type": "ephemeral",
           "dst": "/tmp/",
           "write": true,
@@ -325,8 +332,6 @@ App
           "linkname": "/run/user/150"
         }
       ],
-      "auto_root": "/var/lib/hakurei/base/org.debian",
-      "root_flags": 2,
       "etc": "/etc/",
       "auto_etc": true
     }
@@ -429,6 +434,13 @@ App
     "device": true,
     "filesystem": [
       {
+        "type": "bind",
+        "dst": "/",
+        "src": "/var/lib/hakurei/base/org.debian",
+        "write": true,
+        "autoroot": true
+      },
+      {
         "type": "ephemeral",
         "dst": "/tmp/",
         "write": true,
@@ -474,8 +486,6 @@ App
         "linkname": "/run/user/150"
       }
     ],
-    "auto_root": "/var/lib/hakurei/base/org.debian",
-    "root_flags": 2,
     "etc": "/etc/",
     "auto_etc": true
   }
@@ -632,6 +642,13 @@ func Test_printPs(t *testing.T) {
         "device": true,
         "filesystem": [
           {
+            "type": "bind",
+            "dst": "/",
+            "src": "/var/lib/hakurei/base/org.debian",
+            "write": true,
+            "autoroot": true
+          },
+          {
             "type": "ephemeral",
             "dst": "/tmp/",
             "write": true,
@@ -677,8 +694,6 @@ func Test_printPs(t *testing.T) {
             "linkname": "/run/user/150"
           }
         ],
-        "auto_root": "/var/lib/hakurei/base/org.debian",
-        "root_flags": 2,
         "etc": "/etc/",
         "auto_etc": true
       }
diff --git a/hst/config.go b/hst/config.go
index 8226a35f..e2f95d14 100644
--- a/hst/config.go
+++ b/hst/config.go
@@ -93,17 +93,12 @@ type (
 
 		// pass through all devices
 		Device bool `json:"device,omitempty"`
-		// container mount points
+		// container mount points;
+		// if the first element targets /, it is inserted early and excluded from path hiding
 		Filesystem []FilesystemConfigJSON `json:"filesystem"`
 		// create symlinks inside container filesystem
 		Link []LinkConfig `json:"symlink"`
 
-		// automatically bind mount top-level directories to container root;
-		// the zero value disables this behaviour
-		AutoRoot *container.Absolute `json:"auto_root,omitempty"`
-		// extra flags for AutoRoot
-		RootFlags int `json:"root_flags,omitempty"`
-
 		// read-only /etc directory
 		Etc *container.Absolute `json:"etc,omitempty"`
 		// automatically set up /etc symlinks
diff --git a/hst/hst.go b/hst/hst.go
index 6e77dc98..6654a4b7 100644
--- a/hst/hst.go
+++ b/hst/hst.go
@@ -97,6 +97,7 @@ func Template() *Config {
 				"GOOGLE_DEFAULT_CLIENT_SECRET": "OTJgUOQcT7lO7GsGZq2G4IlT",
 			},
 			Filesystem: []FilesystemConfigJSON{
+				{&FSBind{container.AbsFHSRoot, container.AbsFHSVarLib.Append("hakurei/base/org.debian"), true, false, false, true}},
 				{&FSEphemeral{Target: container.AbsFHSTmp, Write: true, Perm: 0755}},
 				{&FSOverlay{
 					Target: container.MustAbs("/nix/store"),
@@ -111,11 +112,9 @@ func Template() *Config {
 					Target: container.MustAbs("/data/data/org.chromium.Chromium"), Write: true}},
 				{&FSBind{Source: container.AbsFHSDev.Append("dri"), Device: true, Optional: true}},
 			},
-			Link:      []LinkConfig{{container.AbsFHSRunUser.Append("65534"), container.FHSRunUser + "150"}},
-			AutoRoot:  container.AbsFHSVarLib.Append("hakurei/base/org.debian"),
-			RootFlags: container.BindWritable,
-			Etc:       container.AbsFHSEtc,
-			AutoEtc:   true,
+			Link:    []LinkConfig{{container.AbsFHSRunUser.Append("65534"), container.FHSRunUser + "150"}},
+			Etc:     container.AbsFHSEtc,
+			AutoEtc: true,
 		},
 	}
 }
diff --git a/hst/hst_test.go b/hst/hst_test.go
index a3930f48..b8ec79c9 100644
--- a/hst/hst_test.go
+++ b/hst/hst_test.go
@@ -103,6 +103,13 @@ func TestTemplate(t *testing.T) {
 		"device": true,
 		"filesystem": [
 			{
+				"type": "bind",
+				"dst": "/",
+				"src": "/var/lib/hakurei/base/org.debian",
+				"write": true,
+				"autoroot": true
+			},
+			{
 				"type": "ephemeral",
 				"dst": "/tmp/",
 				"write": true,
@@ -148,8 +155,6 @@ func TestTemplate(t *testing.T) {
 				"linkname": "/run/user/150"
 			}
 		],
-		"auto_root": "/var/lib/hakurei/base/org.debian",
-		"root_flags": 2,
 		"etc": "/etc/",
 		"auto_etc": true
 	}
diff --git a/internal/app/container_linux.go b/internal/app/container_linux.go
index b82a6b69..33c0c72a 100644
--- a/internal/app/container_linux.go
+++ b/internal/app/container_linux.go
@@ -74,8 +74,19 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		*gid = container.OverflowGid()
 	}
 
-	if s.AutoRoot != nil {
-		params.Root(s.AutoRoot, s.RootFlags)
+	filesystem := s.Filesystem
+	var autoroot *hst.FSBind
+	// valid happens late, so root mount gets it here
+	if len(filesystem) > 0 && filesystem[0].Valid() && filesystem[0].Path().String() == container.FHSRoot {
+		// if the first element targets /, it is inserted early and excluded from path hiding
+		rootfs := filesystem[0].FilesystemConfig
+		filesystem = filesystem[1:]
+		rootfs.Apply(params.Ops)
+
+		// autoroot requires special handling during path hiding
+		if b, ok := rootfs.(*hst.FSBind); ok && b.Valid() && b.AutoRoot {
+			autoroot = b
+		}
 	}
 
 	params.
@@ -128,7 +139,7 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	}
 
 	var hidePathSourceCount int
-	for i, c := range s.Filesystem {
+	for i, c := range filesystem {
 		if !c.Valid() {
 			return nil, nil, fmt.Errorf("invalid filesystem at index %d", i)
 		}
@@ -138,10 +149,10 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 		hidePathSourceCount += len(c.Host())
 	}
 
-	// AutoRoot is a collection of many BindMountOp internally
+	// AutoRootOp is a collection of many BindMountOp internally
 	var autoRootEntries []fs.DirEntry
-	if s.AutoRoot != nil {
-		if d, err := os.ReadDir(s.AutoRoot.String()); err != nil {
+	if autoroot != nil {
+		if d, err := os.ReadDir(autoroot.Source.String()); err != nil {
 			return nil, nil, err
 		} else {
 			// autoroot counter
@@ -153,17 +164,17 @@ func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid
 	hidePathSource := make([]*container.Absolute, 0, hidePathSourceCount)
 
 	// fs append
-	for _, c := range s.Filesystem {
+	for _, c := range filesystem {
 		// all entries already checked above
 		hidePathSource = append(hidePathSource, c.Host()...)
 	}
 
 	// autoroot append
-	if s.AutoRoot != nil {
+	if autoroot != nil {
 		for _, ent := range autoRootEntries {
 			name := ent.Name()
 			if container.IsAutoRootBindable(name) {
-				hidePathSource = append(hidePathSource, s.AutoRoot.Append(name))
+				hidePathSource = append(hidePathSource, autoroot.Source.Append(name))
 			}
 		}
 	}
diff --git a/internal/app/seal_linux.go b/internal/app/seal_linux.go
index 23d65f95..fb6f39b6 100644
--- a/internal/app/seal_linux.go
+++ b/internal/app/seal_linux.go
@@ -244,8 +244,14 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 			Tty:          true,
 			AutoEtc:      true,
 
-			AutoRoot:  container.AbsFHSRoot,
-			RootFlags: container.BindWritable,
+			Filesystem: []hst.FilesystemConfigJSON{
+				{&hst.FSBind{
+					Target:   container.AbsFHSRoot,
+					Source:   container.AbsFHSRoot,
+					Write:    true,
+					AutoRoot: true,
+				}},
+			},
 		}
 
 		// bind GPU stuff