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OpenWrt: Split Toolchain for faster Firmware Build Times

Sven Bachmann — Sat, 02 Apr 2011 11:47:46 +0000

At work we’re using Hudson to automatically build projects whenever something is changed in a SCM. For most projects you’ll get fast results if your checkin breaks something which you don’t mind because you not always rebuild the complete project. Now, OpenWrt brings its own toolchain, which compiles the complete local and cross-compiling stuff because the compiler on the host is normally a bit behind and does not contain latest fixes for ARM and other architectures. So how to save some time with not compiling the toolchain everytime a project is build?

For this purpose OpenWrt has a feature called “Use External Toolchain”. This makes it possible to also use vendor-specific toolchains to build OpenWrt. What currently not worked was using OpenWrt itself as its external toolchain. To make this possible, I’ve created some patches (send already to the mailing list/bugzilla) and written some short How-To in the OpenWrt Wiki.

So now the Toolchain is rebuild once a week (but can also be triggered by hand) and the normal firmware is build as usual with a git clean -f -d -x at the beginning.

arm: remove thumb instruction “bx lr” from EABI binary

Sven Bachmann — Mon, 14 Sep 2009 04:59:01 +0000

Today I had a strange error using the GCC version 4.4.1 with EABI support on a non thumb-ARMv4. Everytime I compiled something, with and w/o the -mno-thumb-interwork parameter it also contained the bx lr instruction which is only for later ARM processors with thumb support.

The only solution seemed to be to patch the GCC. Urgs… not really a nice solution, because recompiling GCC takes 3 stages and much time. After lots of googling I finally found the solution in the Debian Wiki.

GCC will always compile the new bx lr instruction and its the assemblers and linkers part to replace it with a normal call on normal ARMs. The problem is… GCC doesn’t tell the assembler/linker that it needs to do it. So we have to do it:

CFLAGS += -Xlinker --fix-v4bx -Xassembler --fix-v4bx

Later on… It seemed that a lot of apps in OpenWrt didn’t respect my compiler flags, so I needed to patch GCC. You can find the result here: gcc 4.4.1: ARM – save fix-v4bx flag in linker spec (patch is agains OpenWrt). The plain patch against GCC 4.4.1 is here: gcc-save-fix-v4bx-for-linker.patch. If it turns out that this is the correct kind to do it, I’ll send it to the GCC list.

uClibc: “bx r6″ compile error on ARM

Sven Bachmann — Tue, 08 Sep 2009 08:31:59 +0000

While compiling OpenWrt for an ARM compatible processor I got the following error:

{standard input}: Assembler messages: {standard input}:39: Error: selected processor does not support `bx r6'

I found the solution in the The definitive guide to GCC book from William Von Hagen (I don’t own it, I found it via Google Books). You have to disable the the USE_BX flag in the uClibc config file and everything will be fine.

To make it permanent, go to toolchain/uClibc/config-* (* is your used uClibc version) and copy the default arm file to arm.ARCH where ARCH is the name of the directory in target/linux/ARCH.

Thanks to William, the OpenWrt community and the uClibc folks (and all others who make this a round thing).

OpenWrt 8.09: ssh freischalten

Sven Bachmann — Sun, 31 May 2009 08:24:59 +0000

Da sich bei OpenWrt 8.09 ein wenig geändert hat, ist nun ein etwas anderer Weg notwendig, um von aussen ssh zu nutzen.

Freischalten über LuCI

1. Administration 2. Network->Firewall->Traffic Control 3. Advanced Rules->Add Entry 4. Additional Field->Protocol: Add 5. Name: ssh 6. Source: wan 7. Destination: Device 8. Protocol: TCP 9. Destination Port: 22 10. Action: accept 11. Save & Apply

Freischalten über uci

uci add firewall rule uci set firewall.@rule[-1]._name=ssh uci set firewall.@rule[-1].src=wan uci set firewall.@rule[-1].target=ACCEPT uci set firewall.@rule[-1].proto=tcp uci set firewall.@rule[-1].dest_port=22 uci commit firewall /etc/init.d/firewall start

Das ganze kann auch nochmal bei meiner Quelle, dem OpenWrt Forum nachgelesen werden.

Using a 56k modem with an Asus wl-500g premium router and OpenWrt Kamikaze 7.09

Sven Bachmann — Wed, 26 Mar 2008 15:04:06 +0000

Hi there,

this (easter) weekend, I had to fiddle around with an Asus WLAN router, a 56k modem (yes, in Germany we have places without DSL or similar things) and OpenWrt. And what should I say? It works! Thanks to OpenWrt.

First of all, you need some packages which you can install with ipkg on the router: chat, ppp, various usb modules (see openwrt wiki for details) and the usb-serial module.

To enable wifi, please also see the openwrt documentation – I had to use WAP, because WAP2 was not supported by a windows client – and downloading some 10MB big files just to make it work would not be funny over 56k modem

First step: Set the WAN device from the routers WAN port to the modem device, ppp0

/etc/config/network

config interface wan option ifname 'ppp0' option proto dhcp

Second step: Configure the ppp utils – this will show a config for the provider 1&1

Download: /etc/ppp/chat.1und1

Download: /etc/ppp/opts.1und1

Anlegen der /etc/ppp/pap-secrets.

"1und1/1234-567" * "PASSWORD"

Download: /etc/ppp/ip-up.d/firewall

Third step: Add some webscripts, to manage the connect and disconnect via browser