Merge pull request 'feat: add proper A/B schema' (telent#1) from prei…

…nit-ab into main

Reviewed-on: https://git.dgnum.eu/DGNum/liminix/pulls/1

.gitignore

@@ -7,3 +7,4 @@ _build
 *-secrets.nix
 examples/static-leases.nix
 /doc/hardware.rst
+.ccls-cache

default.nix

@@ -4,7 +4,6 @@
 , liminix-config ? <liminix-config>
 , nixpkgs ? <nixpkgs>
 , borderVmConf ? ./bordervm.conf.nix
-, imageType ? "primary"
 }:
 
 let
@@ -14,8 +13,7 @@ let
     config = {
       allowUnsupportedSystem = true; # mipsel
       permittedInsecurePackages = [
-        "python-2.7.18.6"       # kernel backports needs python <3
-        "python-2.7.18.7"
+        "python-2.7.18.8" # kernel backports needs python <3
       ];
     };
   });
@@ -36,9 +34,6 @@ let
       ./modules/s6
       ./modules/users.nix
       ./modules/outputs.nix
-      {
-        boot.imageType = imageType;
-      }
     ];
   };
   config = eval.config;
@@ -66,6 +61,13 @@ in {
   # cross-compiling nix-shell for any package we're customizing
   inherit pkgs;
 
+  deployEnv = pkgs.mkShell {
+    packages = with pkgs.pkgsBuildBuild; [
+      tufted
+      min-copy-closure
+    ];
+  };
+
   buildEnv = pkgs.mkShell {
     packages = with pkgs.pkgsBuildBuild; [
       tufted

devices/zyxel-nwa50ax/default.nix

@@ -91,7 +91,6 @@
     - Mount the logs partition, mount / as overlayfs of firmware ? rootfs and rootfs_data for extended data.
     - Jitter-based entropy injection? Device can be slow to initialize its CRNG and hostapd will reject few clients at the start because of that.
     - Defaults for hostapd based on MT7915 capabilities? See the example for one possible list.
-    - Remove primary/secondary hack and put it in preinit.
     - Offer ways to reflash the *bootloader* itself to support direct boot via UBI and kernel upgrades via filesystem rewrite.
 
     Vendor web page: https://www.zyxel.com/fr/fr/products/wireless/ax1800-wifi-6-dual-radio-nebulaflex-access-point-nwa50ax
@@ -171,6 +170,8 @@
           maxLEBcount = "256";
         };
 
+        flash.eraseBlockSize = 65536;
+
         # This is a FIT containing a kernel padded and
         # a UBI volume rootfs.
         defaultOutput = "zyxel-nwa-fit";
@@ -181,22 +182,18 @@
         alignment = 2048;
 
         rootDevice = "ubi:rootfs";
+        alternativeRootDevice = "ubi:rootfs";
+
+        # Auto-attach MTD devices: ubi_a then ubi_b.
+        ubi.mtds = [ "ubi_a" "ubi_b" ];
 
         dts = {
-          # Actually, this is not what we want.
-          # This DTS is insufficient.
-          src = ./mt7621_zyxel_nwa50ax.dtsi;
+          # Strong DTB assumptions:
+          # ubi_a and ubi_b are two MTD devices.
+          # If those changes, disaster will occur.
+          src = ./dtb/mt7621_zyxel_nwa50ax.dtsi;
           includes = [
-            # Here's one weird trick to make `ubi` detection
-            # out of the box.
-            # We will write ubi on /dev/firmware_a:rootfs location
-            # and same for /dev/firmware_b:rootfs.
-            # How do we distinguish both?
-            # We can just use the DTS to point ubi at A or B.
-            # This, unfortunately, means that we have "two images".
-            # But they are really just 1 image with 2 different DTS.
-            # TODO: improve this hack in preinit?
-            (if config.boot.imageType == "primary" then "${./a_image}" else "${./b_image}")
+            "${./dtb}"
             "${openwrt.src}/target/linux/ramips/dts"
           ];
         };

devices/zyxel-nwa50ax/a_image/mt7621_zyxel_nwa-ax-for-ab.dtsi → devices/zyxel-nwa50ax/dtb/mt7621_zyxel_nwa-ax-for-ab.dtsi

@@ -56,7 +56,7 @@
 			};
 
 			partition@400000 {
-				label = "ubi";
+				label = "ubi_a";
 				reg = <0x800000 0x2000000>;
 			};
 		};

modules/base.nix

@@ -64,10 +64,6 @@ in {
         default = "bootargs";
         description = "Kernel command line's devicetree node";
       };
-      imageType = mkOption {
-        type = types.enum [ "primary" "secondary" ];
-        default = "primary";
-      };
       imageFormat = mkOption {
         type = types.enum ["fit" "uimage"];
         default = "uimage";
@@ -110,7 +106,10 @@ in {
       "root=${config.hardware.rootDevice}"
       "rootfstype=${config.rootfsType}"
       "fw_devlink=off"
-    ] ++ lib.optional (config.rootOptions != null) "rootflags=${config.rootOptions}";
+    ]
+    ++ (map (mtd: "ubi.mtd=${mtd}") config.hardware.ubi.mtds)
+    ++ lib.optional (config.rootOptions != null) "rootflags=${config.rootOptions}"
+    ++ lib.optional (config.hardware.alternativeRootDevice != null) "altroot=${config.hardware.alternativeRootDevice}";
 
     system.callService = path : parameters :
       let

modules/hardware.nix

@@ -82,6 +82,18 @@ in {
         type = types.str;
         example = "/dev/mtdblock3";
       };
+      alternativeRootDevice = mkOption {
+        description = "Full path to alternative preferred root device (the B partition of your rootfs)";
+        type = types.nullOr types.str;
+        example = "ubi_b:rootfs";
+        default = null;
+      };
+      ubi.mtds = mkOption {
+        description = "List of MTD device to attach";
+        type = types.listOf types.str;
+        example = [ "ubi_a" "ubi_b" "data" ];
+        default = null;
+      };
       networkInterfaces = mkOption {
         type = types.attrsOf types.anything;
       };

modules/outputs/zyxel-nwa-fit.nix

@@ -62,7 +62,7 @@ on a system with pre-existing firmware and OS.
         };
       '';
       in
-      pkgs.runCommand "zyxel-nwa-fit-${config.boot.imageType}" {
+      pkgs.runCommand "zyxel-nwa-fit" {
         nativeBuildInputs = [ pkgs.pkgsBuildBuild.ubootTools pkgs.pkgsBuildBuild.dtc ];
       } ''
         mkimage -f ${dts} $out

pkgs/preinit/opts.h

@@ -1,5 +1,6 @@
 struct root_opts {
     char *device;
+    char *altdevice; /* For A/B schemas */
     char *fstype;
     char *mount_opts;
 };

pkgs/preinit/parseopts.c

@@ -70,6 +70,7 @@ void parseopts(char * cmdline, struct root_opts *opts) {
 	p = eat_param(p, "root=", &(opts->device));
 	p = eat_param(p, "rootfstype=", &(opts->fstype));
 	p = eat_param(p, "rootflags=", &(opts->mount_opts));
+	p = eat_param(p, "altroot=", &(opts->altdevice));
     };
 }
 
@@ -102,6 +103,14 @@ int main()
     expect_equal(opts.fstype, "ubifs");
     expect_equal(opts.mount_opts, "subvol=1");
 
+    // finds altroot= options
+    buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs rootflags=subvol=1 fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0 altroot=/dev/mtdblock6 foo");
+    memset(&opts, '\0', sizeof opts); parseopts(buf, &opts);
+    expect_equal(opts.device, "/dev/mtdblock0");
+    expect_equal(opts.altdevice, "/dev/mtdblock6");
+    expect_equal(opts.fstype, "ubifs");
+    expect_equal(opts.mount_opts, "subvol=1");
+
     // in case of duplicates, chooses the latter
     // also: works if the option is end of string
     buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0");
@@ -134,13 +143,15 @@ int main()
     if(opts.fstype) die("expected null rootfstype, got \"%s\"", opts.fstype);
     if(opts.device) die("expected null root, got \"%s\"", opts.device);
     if(opts.mount_opts) die("expected null mount_opts, got \"%s\"", opts.mount_opts);
+    if(opts.altdevice) die("expected null altdevice, got \"%s\"", opts.altdevice);
 
     // provides empty strings for empty options
-    buf = strdup("liminix rootfstype= fw_devlink=off root= /dev/hda1");
+    buf = strdup("liminix rootfstype= fw_devlink=off root= altroot= /dev/hda1");
     memset(&opts, '\0', sizeof opts);  parseopts(buf, &opts);
 
     if(strlen(opts.fstype)) die("expected empty rootfstype, got \"%s\"", opts.fstype);
-    if(strlen(opts.device)) die("expected null root, got \"%s\"", opts.device);
+    if(strlen(opts.device)) die("expected empty root, got \"%s\"", opts.device);
+    if(strlen(opts.altdevice)) die("expected empty altroot, got \"%s\"", opts.altdevice);
 
     expect_equal("01", pr_u32(1));
     expect_equal("ab", pr_u32(0xab));

pkgs/preinit/preinit.c

@@ -13,7 +13,7 @@
 #include "opts.h"
 
 #define ERR(x) write(2, x, strlen(x))
-#define AVER(c) do { if(c < 0) { ERR("failed: "  #c ": error=0x" ); pr_u32(errno); ERR("\n"); } } while(0)
+#define AVER(c) do { if(c < 0) { ERR("failed: "  #c ": error=0x" ); pr_u32(errno); ERR ( " - "); ERR(strerror(errno)); ERR("\n"); } } while(0)
 
 char * pr_u32(int32_t input);
 
@@ -88,8 +88,21 @@ int main(int argc, char *argv[], char *envp[])
 	    write(1, ", opts=", 7);
 	    write(1, opts.mount_opts, strlen(opts.mount_opts));
 	}
+	if(opts.altdevice) {
+	    write(1, ", altdevice=", 12);
+	    write(1, opts.altdevice, strlen(opts.altdevice));
+	}
 	write(1, ")\n", 2);
-	AVER(mount(opts.device, "/target/persist", opts.fstype, 0, opts.mount_opts));
+
+	if(!opts.altdevice) {
+	    AVER(mount(opts.device, "/target/persist", opts.fstype, 0, opts.mount_opts));
+	} else {
+	    if(mount(opts.device, "/target/persist", opts.fstype, 0, opts.mount_opts) < 0) {
+		AVER(mount(opts.altdevice, "/target/persist", opts.fstype, 0, opts.mount_opts));
+	    }
+	}
+
+	// FUTUREWORK: any failure using `opts.device` should force us to consider rerunning this with the alternative rootfs.
 	AVER(mount("/target/persist/nix", "/target/nix",
 		   "bind", MS_BIND, NULL));
 
@@ -102,6 +115,7 @@ int main(int argc, char *argv[], char *envp[])
 
 	argv[0] = "init";
 	argv[1] = NULL;
+
 	AVER(execve("/persist/init", argv, envp));
     }
     die();