tftp: introduce an alternative command line for TFTP #8

Merged
rlahfa merged 17 commits from strong-tftp into main 2024-09-01 17:48:54 +02:00
23 changed files with 384 additions and 61 deletions

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@ -170,7 +170,7 @@
maxLEBcount = "256";
};
flash.eraseBlockSize = 65536;
flash.eraseBlockSize = 64 * 1024;
# This is a FIT containing a kernel padded and
# a UBI volume rootfs.
@ -181,8 +181,8 @@
# Aligned on 2kb.
alignment = 2048;
rootDevice = "ubi:rootfs";
alternativeRootDevice = "ubi:rootfs";
rootDevice = "ubi0:rootfs";
alternativeRootDevice = "ubi1:rootfs";
# Auto-attach MTD devices: ubi_a then ubi_b.
ubi.mtds = [ "ubi_a" "ubi_b" ];
@ -224,6 +224,7 @@
tftp = {
# 5MB is nice.
freeSpaceBytes = 5 * 1024 * 1024;
appendDTB = true;
loadAddress = lim.parseInt "0x2000000";
};
};

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@ -8,6 +8,7 @@
./bridge
./busybox.nix
./dhcp6c
./jitter-rng
./dnsmasq
./firewall
./hardware.nix

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@ -14,5 +14,8 @@
boot.commandLine = [
"console=ttyS0,115200" # true of all mips we've yet encountered
];
boot.tftp.commandLine = [
"console=ttyS0,115200" # true of all mips we've yet encountered
];
};
}

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@ -109,7 +109,13 @@ in {
]
++ (map (mtd: "ubi.mtd=${mtd}") config.hardware.ubi.mtds)
++ lib.optional (config.rootOptions != null) "rootflags=${config.rootOptions}"
++ lib.optional (config.hardware.alternativeRootDevice != null) "altroot=${config.hardware.alternativeRootDevice}";
++ lib.optional (config.hardware.alternativeRootDevice != null) "rootalt=${config.hardware.alternativeRootDevice}";
boot.tftp.commandLine = [
"panic=10 oops=panic init=/bin/init loglevel=8"
"fw_devlink=off"
"rootfstype=${config.rootfsType}"
];
system.callService = path : parameters :
let

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@ -20,6 +20,7 @@ in
system.service.bridge = {
primary = mkOption { type = liminix.lib.types.serviceDefn; };
members = mkOption { type = liminix.lib.types.serviceDefn; };
ready = mkOption { type = liminix.lib.types.serviceDefn; };
};
};
config.system.service.bridge = {
@ -28,6 +29,12 @@ in
type = types.str;
description = "bridge interface name to create";
};
macAddressFromInterface = mkOption {
type = types.nullOr liminix.lib.types.service;
default = null;
description = "reuse mac address from an existing interface service";
};
};
members = config.system.callService ./members.nix {
primary = mkOption {
@ -40,6 +47,19 @@ in
description = "interfaces to add to the bridge";
};
};
# TODO: generalize it outside
ready = config.system.callService ./ready.nix {
primary = mkOption {
type = liminix.lib.types.service;
description = "primary bridge interface";
};
members = mkOption {
type = liminix.lib.types.service;
description = "members service";
};
};
};
config.kernel.config = {
BRIDGE = "y";

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@ -10,22 +10,21 @@ let
inherit (liminix.networking) interface;
inherit (liminix.services) bundle oneshot;
inherit (lib) mkOption types;
addif = member :
# how do we get sight of services from here? maybe we need to
# implement ifwait as a regualr derivation instead of a
# servicedefinition
svc.ifwait.build {
state = "running";
interface = member;
dependencies = [ primary member ];
service = oneshot {
name = "${primary.name}.member.${member.name}";
up = ''
ip link set dev $(output ${member} ifname) master $(output ${primary} ifname)
'';
down = "ip link set dev $(output ${member} ifname) nomaster";
};
};
addif = member : oneshot {
name = "${primary.name}.member.${member.name}";
up = ''
echo "waiting for bridge $(output ${primary} ifname) to be ready"
${ifwait}/bin/ifwait -v $(output ${primary} ifname) running
echo "attaching $(output ${member} ifname) to $(output ${primary} ifname) bridge"
ip link set dev $(output ${member} ifname) master $(output ${primary} ifname)
'';
down = ''
echo "detaching $(output ${member} ifname) from any bridge"
ip link set dev $(output ${member} ifname) nomaster
'';
dependencies = [ primary member ];
};
in bundle {
name = "${primary.name}.members";
contents = map addif members;

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@ -3,15 +3,24 @@
, ifwait
, lib
}:
{ ifname } :
{ ifname, macAddressFromInterface ? null } :
let
inherit (liminix.services) bundle oneshot;
inherit (lib) mkOption types;
inherit (lib) mkOption types optional;
in oneshot rec {
name = "${ifname}.link";
up = ''
ip link add name ${ifname} type bridge
${liminix.networking.ifup name ifname}
${if macAddressFromInterface == null then
"ip link add name ${ifname} type bridge"
else
"ip link add name ${ifname} address $(output ${macAddressFromInterface} ether) type bridge"}
(in_outputs ${name}
echo ${ifname} > ifname
cat /sys/class/net/${ifname}/address > ether
)
'';
down = "ip link set down dev ${ifname}";
down = "ip link delete ${ifname}";
dependencies = optional (macAddressFromInterface != null) macAddressFromInterface;
}

18
modules/bridge/ready.nix Normal file
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@ -0,0 +1,18 @@
{
liminix
, ifwait
, lib
}:
{ primary, members } :
let
inherit (liminix.services) oneshot;
in oneshot {
name = "${primary.name}.oper";
up = ''
ip link set up dev $(output ${primary} ifname)
${ifwait}/bin/ifwait -v $(output ${primary} ifname) running
'';
down = "ip link set down dev $(output ${primary} ifname)";
dependencies = [ members ];
}

View file

@ -26,6 +26,10 @@ in {
interface = mkOption {
type = liminix.lib.types.service;
};
package = mkOption {
type = types.package;
default = pkgs.hostapd;
};
params = mkOption {
type = types.attrs;
};

View file

@ -1,10 +1,9 @@
{
liminix
, hostapd
, writeText
, lib
}:
{ interface, params} :
{ package, interface, params } :
let
inherit (liminix.services) longrun;
inherit (lib) concatStringsSep mapAttrsToList;
@ -35,5 +34,5 @@ let
in longrun {
inherit name;
dependencies = [ interface ];
run = "${hostapd}/bin/hostapd -i $(output ${interface} ifname) -P /run/${name}.pid -S ${conf}";
run = "${package}/bin/hostapd -i $(output ${interface} ifname) -P /run/${name}.pid -S ${conf}";
}

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@ -0,0 +1,21 @@
## CPU Jitter RNG
## ==============
##
## CPU Jitter RNG is a random number generator # providing non-physical true
## random generation # that works equally for kernel and user-land. It relies
## on the availability of a high-resolution timer.
{ lib, pkgs, ... }:
let
inherit (lib) mkOption types;
inherit (pkgs) liminix;
in {
options.system.service.jitter-rng = mkOption {
type = liminix.lib.types.serviceDefn;
};
config = {
system.service.jitter-rng = pkgs.liminix.callService ./jitter-rng.nix {
};
};
}

View file

@ -0,0 +1,18 @@
{
liminix
, lib
, jitterentropy-rngd
}:
{ }:
let
inherit (liminix.services) longrun;
name = "jitterentropy-rngd";
in
longrun {
# Does it need to be unique?
inherit name;
run = ''
mkdir -p /run/jitterentropy-rngd
${jitterentropy-rngd}/bin/jitterentropy-rngd -v -p /run/jitterentropy-rngd/${name}.pid
'';
}

View file

@ -17,7 +17,7 @@ let
ip address replace $ip/$mask dev $interface
(in_outputs ${name}
for i in lease mask ip router siaddr dns serverid subnet opt53 interface ; do
printenv $i > $i
(printenv $i || true) > $i
done)
}
case $action in
@ -40,7 +40,7 @@ let
'';
in longrun {
inherit name;
run = "/bin/udhcpc -f -i $(output ${interface} ifname) -x hostname:$(cat /proc/sys/kernel/hostname) -s ${script}";
run = "exec /bin/udhcpc -f -i $(output ${interface} ifname) -x hostname:$(cat /proc/sys/kernel/hostname) -s ${script}";
notification-fd = 10;
dependencies = [ interface ];
}

View file

@ -5,7 +5,8 @@
, ...
}:
let
inherit (lib) mkIf mkOption types;
inherit (pkgs) liminix;
inherit (lib) mkIf;
o = config.system.outputs;
in
{
@ -24,17 +25,10 @@ in
};
boot.initramfs.enable = true;
system.outputs = {
rootfs =
let
inherit (pkgs.pkgsBuildBuild) runCommand mtdutils;
endian = if pkgs.stdenv.isBigEndian
then "--big-endian" else "--little-endian";
in runCommand "make-jffs2" {
depsBuildBuild = [ mtdutils ];
} ''
tree=${o.bootablerootdir}
(cd $tree && mkfs.jffs2 --compression-mode=size ${endian} -e ${toString config.hardware.flash.eraseBlockSize} --enable-compressor=lzo --pad --root . --output $out --squash --faketime )
'';
rootfs = liminix.builders.jffs2 {
bootableRootDirectory = o.bootablerootdir;
inherit (config.hardware.flash) eraseBlockSize;
};
};
};
}

View file

@ -0,0 +1,14 @@
/dts-v1/;
/ {
description = "Liminix TFTP bootscript";
#address-cells = <1>;
images {
bootscript {
description = "Bootscript";
data = /incbin/("boot.scr");
type = "script";
compression = "none";
};
};

View file

@ -5,10 +5,18 @@
, ...
}:
let
inherit (lib) mkOption types concatStringsSep;
inherit (lib) mkOption mkIf types concatStringsSep;
inherit (pkgs) liminix;
cfg = config.boot.tftp;
hw = config.hardware;
arch = pkgs.stdenv.hostPlatform.linuxArch;
# UBI cannot run on the top of phram.
needsSquashfs = config.rootfsType == "ubifs";
rootfstype = if needsSquashfs then "squashfs" else config.rootfsType;
rootfs = if needsSquashfs then
liminix.builders.squashfs config.filesystem.contents
else config.system.outputs.rootfs;
in {
imports = [ ../ramdisk.nix ];
options.boot.tftp = {
@ -28,6 +36,14 @@ in {
type = types.bool;
default = false;
};
commandLine = mkOption {
type = types.listOf types.str;
default = config.boot.commandLine;
description = ''
TFTP-specific command line.
Defaults to the classical one if unset.
'';
};
};
options.system.outputs = {
tftpboot = mkOption {
@ -51,11 +67,52 @@ in {
It uses the Linux `phram <https://github.com/torvalds/linux/blob/master/drivers/mtd/devices/phram.c>`_ driver to emulate a flash device using a segment of physical RAM.
'';
};
tftpboot-fit = mkOption {
type = types.package;
description = ''
tftpboot-fit
************
This output is a variant that encloses the `boot.scr` in a FIT
if that's simpler to transfer for you.
'';
};
};
config = {
boot.ramdisk.enable = true;
kernel.config = mkIf needsSquashfs {
SQUASHFS = "y";
SQUASHFS_XZ = "y";
};
system.outputs = rec {
tftpboot-fit =
let
tftpboot-fit = pkgs.writeText "tftpboot.its" ''
/dts-v1/;
/ {
description = "Liminix TFTP bootscript";
#address-cells = <1>;
images {
bootscript {
description = "Bootscript";
data = /incbin/("${tftpboot}/boot.scr");
type = "script";
compression = "none";
};
};
};
'';
in
pkgs.runCommand "tftpboot-fit" { nativeBuildInputs = with pkgs.pkgsBuildBuild; [ ubootTools ]; } ''
mkdir -p $out/
cp -rf ${tftpboot}/* $out/
mkimage -f ${tftpboot-fit} $out/script.ub
'';
tftpboot =
let
inherit (pkgs.lib.trivial) toHexString;
@ -69,7 +126,7 @@ in {
zimage = "bootz";
}; in choices.${cfg.kernelFormat};
cmdline = concatStringsSep " " config.boot.commandLine;
cmdline = concatStringsSep " " config.boot.tftp.commandLine;
objcopy = "${pkgs.stdenv.cc.bintools.targetPrefix}objcopy";
stripAndZip = ''
${objcopy} -O binary -R .reginfo -R .notes -R .note -R .comment -R .mdebug -R .note.gnu.build-id -S vmlinux.elf vmlinux.bin
@ -84,7 +141,7 @@ in {
hex() { printf "0x%x" $1; }
rootfsStart=${toString cfg.loadAddress}
rootfsSize=$(binsize64k ${o.rootfs} )
rootfsSize=$(binsize64k ${rootfs} )
rootfsSize=$(($rootfsSize + ${toString cfg.freeSpaceBytes} ))
ln -s ${o.manifest} manifest
@ -98,13 +155,13 @@ in {
dtbStart=$(($rootfsStart + $rootfsSize))
${if cfg.compressRoot
then ''
lzma -z9cv ${o.rootfs} > rootfs.lz
lzma -z9cv ${rootfs} > rootfs.lz
rootfsLzStart=$dtbStart
rootfsLzSize=$(binsize rootfs.lz)
dtbStart=$(($dtbStart + $rootfsLzSize))
''
else ''
ln -s ${o.rootfs} rootfs
ln -s ${rootfs} rootfs
''
}
@ -121,7 +178,7 @@ in {
fdtput -p -t s dtb /reserved-memory/$node compatible phram
fdtput -p -t lx dtb /reserved-memory/$node reg $ac_prefix $(hex $rootfsStart) $sz_prefix $(hex $rootfsSize)
cmd="liminix ${cmdline} mtdparts=phram0:''${rootfsSize}(rootfs) phram.phram=phram0,''${rootfsStart},''${rootfsSize},${toString config.hardware.flash.eraseBlockSize} root=/dev/mtdblock0";
cmd="liminix ${cmdline} mtdparts=phram0:''${rootfsSize}(rootfs) phram.phram=phram0,''${rootfsStart},''${rootfsSize},${toString config.hardware.flash.eraseBlockSize} rootfstype=${rootfstype} root=/dev/mtdblock0";
fdtput -t s dtb /chosen ${config.boot.commandLineDtbNode} "$cmd"
dtbSize=$(binsize ./dtb )

83
modules/pki/default.nix Normal file
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@ -0,0 +1,83 @@
{ config, lib, pkgs, ... }:
# Inspired from nixpkgs/NixOS.
with lib;
let
inherit (pkgs.pseudofile) dir symlink;
cfg = config.security.pki;
cacertPackage = pkgs.cacert.override {
blacklist = [ ];
extraCertificateFiles = cfg.certificateFiles;
extraCertificateStrings = cfg.certificates;
};
caBundleName = "ca-bundle.crt";
caBundle = "${cacertPackage}/etc/ssl/certs/${caBundleName}";
in
{
options = {
security.pki.installCACerts = mkEnableOption "installing CA certificates to the system" // {
default = false;
};
security.pki.certificateFiles = mkOption {
type = types.listOf types.path;
default = [];
example = literalExpression ''[ "''${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt" ]'';
description = ''
A list of files containing trusted root certificates in PEM
format. These are concatenated to form
{file}`/etc/ssl/certs/ca-certificates.crt`, which is
used by many programs that use OpenSSL, such as
{command}`curl` and {command}`git`.
'';
};
security.pki.certificates = mkOption {
type = types.listOf types.str;
default = [];
example = literalExpression ''
[ '''
NixOS.org
=========
-----BEGIN CERTIFICATE-----
MIIGUDCCBTigAwIBAgIDD8KWMA0GCSqGSIb3DQEBBQUAMIGMMQswCQYDVQQGEwJJ
TDEWMBQGA1UEChMNU3RhcnRDb20gTHRkLjErMCkGA1UECxMiU2VjdXJlIERpZ2l0
...
-----END CERTIFICATE-----
'''
]
'';
description = ''
A list of trusted root certificates in PEM format.
'';
};
};
config = mkIf cfg.installCACerts {
# NixOS canonical location + Debian/Ubuntu/Arch/Gentoo compatibility.
filesystem = dir {
etc = dir {
ssl = dir {
certs = dir {
"ca-certificates.crt" = symlink caBundle;
"ca-bundle.crt" = symlink caBundle;
};
};
# CentOS/Fedora compatibility.
pki = dir {
certs = dir {
"ca-bundle.crt" = symlink caBundle;
};
};
};
};
};
}

View file

@ -143,6 +143,42 @@ extraPkgs // {
});
in h.override { openssl = null; sqlite = null; };
hostapd-radius =
let
config = [
"CONFIG_DRIVER_NL80211=y"
"CONFIG_DRIVER_WIRED=y"
"CONFIG_EAP=y"
"CONFIG_EAP_PEAP=y"
"CONFIG_RADIUS_SERVER=y"
"CONFIG_FULL_DYNAMIC_VLAN=y"
"CONFIG_IAPP=y"
"CONFIG_IEEE80211AC=y"
"CONFIG_IEEE80211AX=y"
"CONFIG_IEEE80211N=y"
"CONFIG_IEEE80211W=y"
"CONFIG_INTERNAL_LIBTOMMATH=y"
"CONFIG_INTERNAL_LIBTOMMATH_FAST=y"
"CONFIG_IPV6=y"
"CONFIG_LIBNL32=y"
"CONFIG_PKCS12=y"
"CONFIG_RSN_PREAUTH=y"
# Required to read the key material for RADIUS.
"CONFIG_TLS=openssl"
];
h = prev.hostapd.overrideAttrs(o: {
extraConfig = "";
configurePhase = ''
cat > hostapd/defconfig <<EOF
${builtins.concatStringsSep "\n" config}
EOF
${o.configurePhase}
'';
});
in h.override { sqlite = null; };
kexec-tools-static = prev.kexec-tools.overrideAttrs(o: {
# For kexecboot we copy kexec into a ramdisk on the system being
# upgraded from. This is more likely to work if kexec is
@ -168,6 +204,11 @@ extraPkgs // {
patches = (if o ? patches then o.patches else []) ++ [
./pkgs/mtdutils/0001-mkfs.jffs2-add-graft-option.patch
];
postInstall = ''
# Testing programs which we don't need. We save a lot of space!
rm -rf $out/libexec
'';
});
nftables = prev.nftables.overrideAttrs(o: {

View file

@ -13,6 +13,7 @@ in {
liminix = {
builders = {
squashfs = callPackage ./liminix-tools/builders/squashfs.nix {};
jffs2 = callPackage ./liminix-tools/builders/jffs2.nix {};
dtb = callPackage ./kernel/dtb.nix {};
uimage = callPackage ./kernel/uimage.nix {};
kernel = callPackage ./kernel {};

View file

@ -19,11 +19,11 @@
(match v
;; - up: Reflects the administrative state of the interface (IFF_UP)
;; - running: Reflects the operational state (IFF_RUNNING).
{:event "newlink" :name params.link :up :yes :running :yes}
{:event "newlink" :name params.link :up "yes" :running "yes"}
{:present true :up true :running true}
{:event "newlink" :name params.link :up :yes}
{:present :true :up true}
{:event "newlink" :name params.link :up "yes"}
{:present true :up true}
{:event "newlink" :name params.link}
{:present true }

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@ -0,0 +1,17 @@
{
stdenv
, busybox
, buildPackages
, callPackage
, pseudofile
, runCommand
, writeText
} : { eraseBlockSize, bootableRootDirectory }:
let
endian = if stdenv.isBigEndian then "--big-endian" else "--little-endian";
in runCommand "frob-jffs2" {
depsBuildBuild = [ buildPackages.mtdutils ];
} ''
tree=${bootableRootDirectory}
(cd $tree && mkfs.jffs2 --compression-mode=size ${endian} -e ${toString eraseBlockSize} --enable-compressor=lzo --pad --root . --output $out --squash --faketime)
''

View file

@ -9,6 +9,7 @@
ip link set up dev ${ifname}
(in_outputs ${name}
echo ${ifname} > ifname
cat /sys/class/net/${ifname}/address > ether
)
'';
}

View file

@ -65,13 +65,18 @@ static char * eat_param(char *p, char *param_name, char **out)
return p;
}
#define SCAN_CMDLINE(cmdline, identifier, field) do { \
for (char* p = strdup(cmdline); *p; p++) { \
p = eat_param(p, identifier, &(opts->field)); \
} \
} while(0)
void parseopts(char * cmdline, struct root_opts *opts) {
for(char *p = cmdline; *p; p++) {
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));
};
SCAN_CMDLINE(cmdline, "root=", device);
SCAN_CMDLINE(cmdline, "rootfstype=", fstype);
SCAN_CMDLINE(cmdline, "rootflags=", mount_opts);
SCAN_CMDLINE(cmdline, "rootalt=", altdevice);
}
#ifdef TESTS
@ -85,6 +90,8 @@ void parseopts(char * cmdline, struct root_opts *opts) {
#define S(x) #x
#define expect_equal(actual, expected) \
if(!actual || strcmp(actual, expected)) die("%d: expected \"%s\", got \"%s\"", __LINE__, expected, actual);
#define expect_null(actual) \
if (actual) die("%d: expected null, got \"%s\"", __LINE__, actual);
int main()
@ -92,6 +99,7 @@ int main()
struct root_opts opts = {
.device = "/dev/hda1",
.fstype = "xiafs",
.altdevice = NULL,
.mount_opts = NULL
};
char *buf;
@ -103,14 +111,22 @@ 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");
// finds rootalt= 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 rootalt=/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");
// Ensure that `altdevice` is NULL.
buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 fw_devlink=off rootfstype=ubifs mtdparts=phram0:19791872(rootfs) phram.phram=phram0,33554432,19791872,65536 rootfstype=jffs2 root=/dev/mtdblock0");
memset(&opts, '\0', sizeof opts); parseopts(buf, &opts);
expect_equal(opts.device, "/dev/mtdblock0");
expect_null(opts.altdevice);
expect_equal(opts.fstype, "jffs2");
expect_null(opts.mount_opts);
// 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");
@ -146,12 +162,12 @@ int main()
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= altroot= /dev/hda1");
buf = strdup("liminix rootfstype= fw_devlink=off root= rootalt= /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 empty root, got \"%s\"", opts.device);
if(strlen(opts.altdevice)) die("expected empty altroot, got \"%s\"", opts.altdevice);
if(strlen(opts.altdevice)) die("expected empty rootalt, got \"%s\"", opts.altdevice);
expect_equal("01", pr_u32(1));
expect_equal("ab", pr_u32(0xab));