From 0cf49f501356f9644b7174ce1f010a794abda0bd Mon Sep 17 00:00:00 2001 From: Rob Landley Date: Fri, 29 May 2020 04:12:53 -0500 Subject: Fluff out the FAQ some more and flush pending README changes. Yes, I need to convert to README.md, it's on the todo list... --- README | 95 +++++++++++++++++++++++-------------------- www/faq.html | 131 +++++++++++++++++++++++++++++++++++++++++++++++------------ 2 files changed, 157 insertions(+), 69 deletions(-) diff --git a/README b/README index 4b3dee00..d24936f5 100644 --- a/README +++ b/README @@ -30,15 +30,16 @@ Or maybe: LDFLAGS="--static" CROSS_COMPILE=armv5l- make defconfig toybox PREFIX=/path/to/root/filesystem/bin make install_flat -The file "configure" defines default values for many environment -variables that control the toybox build; if you set a value for any of -these, your value is used instead of the default in that file. +The file "configure" defines default values for many environment variables +that control the toybox build; if export any these variables into your +environment, your value is used instead of the default in that file. The CROSS_COMPILE argument above is optional, the default builds a version of toybox to run on the current machine. Cross compiling requires an appropriately -prefixed cross compiler toolchain, several example toolchains are available at: +prefixed cross compiler toolchain, several example toolchains (built using +the file "scripts/mcm-buildall.sh" in the toybox source) are available at: - http://landley.net/aboriginal/bin + https://mkroot.musl.cc/latest/ For the "CROSS_COMPILE=armv5l-" example above, download cross-compiler-armv5l.tar.bz2, extract it, and add its "bin" subdirectory to @@ -47,11 +48,13 @@ includes a dash.) For more about cross compiling, see: + https://landley.net/toybox/faq.html#cross http://landley.net/writing/docs/cross-compiling.html http://landley.net/aboriginal/architectures.html -For a more thorough description of the toybox build process, see -http://landley.net/toybox/code.html#building +For a more thorough description of the toybox build process, see: + + http://landley.net/toybox/code.html#building --- Using toybox @@ -61,82 +64,85 @@ Installing toybox adds symlinks for each command name to the $PATH. The special "toybox" command treats its first argument as the command to run. With no arguments, it lists available commands. This allows you to use toybox -without installing it. This is the only command that can have an arbitrary +without installing it, and is the only command that can have an arbitrary suffix (hence "toybox-armv5l"). -The "help" command provides information about each command (ala "help cat"). +The "help" command provides information about each command (ala "help cat"), +and "help toybox" provides general information about toybox. --- Configuring toybox It works like the Linux kernel: allnoconfig, defconfig, and menuconfig edit a ".config" file that selects which features to include in the resulting -binary. You can save and re-use your .config file, although may want to +binary. You can save and re-use your .config file, but may want to run "make oldconfig" to re-run the dependency resolver when migrating to new versions. The maximum sane configuration is "make defconfig": allyesconfig isn't -recommended for toybox because it enables unfinished commands and debug code. +recommended as a starting point for toybox because it enables unfinished +commands, debug code, and optional dependencies your build environment may +not provide. --- Creating a Toybox-based Linux system -Toybox is not a complete operating system, it's a program that runs under -an operating system. Booting a simple system to a shell prompt requires -three packages: an operating system kernel (Linux*) to drive the hardware, -one or more programs for the system to run (toybox), and a C library ("libc") -to tie them together (toybox has been tested with musl, uClibc, glibc, -and bionic). +Toybox has a built-in simple system builder (scripts/mkroot.sh) with a +Makefile target: -The C library is part of a "toolchain", which is an integrated suite -of compiler, assembler, and linker, plus the standard headers and libraries -necessary to build C programs. (And miscellaneous binaries like nm and objdump.) + make root + sudo chroot root/host/fs /init -Static linking (with the --static option) copies the shared library contents -into the program, resulting in larger but more portable programs, which -can run even if they're the only file in the filesystem. Otherwise, -the "dynamically" linked programs require the library files to be present on -the target system ("man ldd" and "man ld.so" for details). +Type "exit" to get back out. If you install appropriate cross compilers and +point it at Linux source code, it can build simple three-package systems +that boot to a shell prompt under qemu: -An example toybox-based system is Aboriginal Linux: + make root CROSS_COMPILE=sh4-linux-musl- LINUX=~/linux + cd root/sh4 + ./qemu-sh4.sh - http://landley.net/aboriginal/about.html +By calling scripts/mkroot.sh directly you can add additional packages +to the build, see scripts/root/dropbear as an example. -That's designed to run under qemu, emulating several different hardware -architectures (x86, x86-64, arm, mips, sparc, powerpc, sh4). Each toybox -release is regression tested by building Linux From Scratch under this -toybox-based system on each supported architecture, using QEMU to emulate -big and little endian systems with different word size and alignment -requirements. (The eventual goal is to replace Linux From Scratch with -the Android Open Source Project.) +The FAQ explains this in a lot more detail: -* Or something providing the same API such as FreeBSD's Linux emulation layer. + https://landley.net/toybox/faq.html#system + https://landley.net/toybox/faq.html#mkroot --- Presentations 1) "Why Toybox?" talk at the Embedded Linux Conference in 2013 - video: http://youtu.be/SGmtP5Lg_t0 outline: http://landley.net/talks/celf-2013.txt - linked from http://landley.net/toybox/ in nav bar on left as "Why is it?" - - march 21, 2013 entry has section links. + video: http://youtu.be/SGmtP5Lg_t0 + + The https://landley.net/toybox/about.html page has nav links breaking that + talk down into sections. 2) "Why Public Domain?" The rise and fall of copyleft, Ohio LinuxFest 2013 - audio: https://archive.org/download/OhioLinuxfest2013/24-Rob_Landley-The_Rise_and_Fall_of_Copyleft.mp3 outline: http://landley.net/talks/ohio-2013.txt + audio: https://archive.org/download/OhioLinuxfest2013/24-Rob_Landley-The_Rise_and_Fall_of_Copyleft.mp3 3) Why did I do Aboriginal Linux (which led me here) 260 slide presentation: - https://speakerdeck.com/landley/developing-for-non-x86-targets-using-qemu + https://speakerdeck.com/landley/developing-for-non-x86-targets-using-qemu How and why to make android self-hosting: http://landley.net/aboriginal/about.html#selfhost + More backstory than strictly necessary: + https://landley.net/aboriginal/history.html + 4) What's new with toybox (ELC 2015 status update): video: http://elinux.org/ELC_2015_Presentations outline: http://landley.net/talks/celf-2015.txt +5) Toybox vs BusyBox (2019 ELC talk): + + outline: http://landley.net/talks/elc-2019.txt + video: https://www.youtube.com/watch?v=MkJkyMuBm3g + --- Contributing The three important URLs for communicating with the toybox project are: @@ -155,9 +161,9 @@ the easy thing to do is: Then send a file attachment. The list holds messages from non-subscribers for moderation, but I usually get to them in a day or two. -Although I do accept pull requests on github, I download the patches and -apply them with "git am" (which avoids gratuitous merge commits). Closing -the pull request is then the submitter's responsibility. +I download github pull requests as patches and apply them with "git am" +(which avoids gratuitous merge commits). Sometimes I even remember to close +the pull request. If I haven't responded to your patch after one week, feel free to remind me of it. @@ -167,3 +173,6 @@ upstream first (into vanilla toybox, with discussion on the toybox mailing list) and then be pulled into android's toybox repo from there. (They generally resync on fridays). The exception is patches to their build scripts (Android.mk and the checked-in generated/* files) which go directly to AOSP. + +(As for the other meaning of "contributing", https://patreon.com/landley is +always welcome but I warn you up front I'm terrible about updating it.) diff --git a/www/faq.html b/www/faq.html index 5e054f02..ffc90d86 100755 --- a/www/faq.html +++ b/www/faq.html @@ -18,7 +18,11 @@ @@ -271,14 +275,14 @@ project, built by running toybox's scripts/mcm-buildall.sh in that directory, and then symlink the resulting "ccc" subdirectory into toybox where "make root CROSS=" can find them, ala:

-
+
 cd ~
 git clone https://github.com/landley/toybox
 git clone https://github.com/richfelker/musl-cross-make
 cd musl-cross-make
 ../toybox/scripts/mcm-buildall.sh # this takes a while
 ln -s $(realpath ccc) ../toybox/ccc
-

+

Instead of symlinking ccc, you can specify a CROSS_COMPILE= prefix in the same format the Linux kernel build uses. You can either provide a @@ -286,15 +290,15 @@ full path in the CROSS_COMPILE string, or add the appropriate bin directory to your $PATH. I.E:

-

make LDFLAGS=--static CROSS_COMPILE=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin/m68k-linux-musl- distclean defconfig toybox

+

make LDFLAGS=--static CROSS_COMPILE=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin/m68k-linux-musl- distclean defconfig toybox

Is equivalent to:

-

+

export "PATH=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin:$PATH"
LDFLAGS=--static make distclean defconfig toybox CROSS=m68k-linux-musl- -

+

Note: a non-static build won't run unless you install musl on your host. In theory you could "make root" a dynamic root filesystem with musl by copying @@ -310,7 +314,7 @@ libc used by Android. To turn it into something toybox can use, you just have to add an appropriately prefixed "cc" symlink to the other prefixed tools, ala:

-
+
 unzip android-ndk-r21b-linux-x86_64.zip
 cd android-ndk-21b/toolchains/llvm/prebuilt/linux-x86_64/bin
 ln -s x86_64-linux-android29-clang x86_64-linux-android-cc
@@ -318,7 +322,7 @@ PATH="$PWD:$PATH"
 cd ~/toybox
 make distclean
 make LDFLAGS=--static CROSS_COMPILE=x86_64-linux-android- defconfig toybox
-

+

Again, you need a static link unless you want to install bionic on your host. Binaries statically linked against bionic are almost as big as with @@ -330,44 +334,116 @@ against bionic will segfault before calling main() if /dev/null isn't present, and the init script written by mkroot.sh has to run a shell linked against bionic in order to mount devtmpfs on /dev to provide /dev/null.

+ +

Q: Where does toybox fit into the Linux/Android ecosystem?
+(I.E. What part +of the operating system does toybox provide, and what does it depend on?)

+ +

A: Toybox is a set of standard Linux command line +utilities, so that three packages (a Linux kernel, C library, and toybox) +provide a complete bootable unix-style command line system. Toybox provides a command +shell and over a hundred different commands to call from that command shell.

+ +

Toybox is not a complete operating system, it's a program that runs under +an operating system. Booting a simple system to a shell prompt requires +an kernel (such as Linux, or BSD with a Linux emulation layer) +to drive the hardware, one or more programs for the system to run (toybox), +and a C library ("libc") to connect them together (toybox has been tested with +musl, uClibc, glibc, and bionic).

+ +

The C library is delivered as part of a "toolchain", which is an integrated +suite of compiler, assembler, and linker, plus the standard headers and +libraries necessary to build C programs. (And miscellaneous binaries like +nm and objdump.)

+ +

Static linking (with the --static option) copies the shared library contents +into the program, resulting in larger but more portable programs, which +can run even if they're the only file in the filesystem. Otherwise, +the "dynamically" linked programs require the shared library files to be +present on the target system, either copied from the toolchain or built +again from source (with potential version skew if they don't match the toolchain +versions exactly). See +"man ldd", +"man ld.so", +and "man libc" for details.

+ +

Toybox has a policy of requiring no external dependencies other than the +C library for defconfig builds. You can optionally enable support for +additional libraries in menuconfig (such as openssl, zlib, or selinux), +but toybox either provides its own built-in versions of such functionality +(which the libraries provide larger, more complex, often assembly optimized +alternatives to), or allows things like selinux support to cleanly drop +out.

+ +

Most embedded systems will add a fourth package to the kernel/libc/cmdline +above containing dedicated "application" that the embedded system exists to +run, plus any other packages that application depends on. +Build systems will add a native version of the toolchain packages so +they can build additional software on the resulting system. Desktop systems +will add a GUI and additional application packages like web browsers +and video players. A linux distro like Debian would add hundreds of packages. +Android adds around a thousand.

+ +

But all of these systems conceptually sit on a common three-package +"kernel/libc/cmdline" base, and toybox aims to provide a simple, reproducible, +auditable version of the cmdline portion of that base.

+

Q: How do you build a working Linux system with toybox?

-

A: To build a native chroot, "make root" then "sudo chroot -root/host/fs /init". Type "exit" to get back out.

+

A: Toybox has a built-in system builder, which has a Makefile target. +To build a native root filesystem you can chroot into, +"make root" then "sudo chroot +root/host/fs /init" to enter it. Type "exit" to get back out.

-

You can also cross compile simple two package (toybox+linux) systems that -boot to a shell prompt under qemu, by specifying -a target type with CROSS= +

You can also cross compile simple three package (toybox+libc+linux) +systems that boot to a shell prompt under qemu, +by specifying a target type with CROSS= (or setting CROSS_COMPILE= to a cross compiler prefix with optional absolute path), and pointing the build at a Linux kernel source directory, ala:

make root CROSS=sh4 LINUX=~/linux

Then you can cd root/sh4; ./qemu-sh4.sh to launch the emulator -(you need the appropriate qemu-system-* binary installed). Type "exit" +(you need the appropriate qemu-system-* binary installed, it'll complain +if it can't find it). Type "exit" when done and it should shut down the emulator on the way out.

-

The cross compilers I test this with are built from the musl-libc +

The build finds the three packages needed to produce +this system because 1) you're in a toybox source directory, 2) your cross +compiler has a libc built into it, 3) you tell it where to find a Linux kernel +source directory with LINUX= on the command line. (If you don't say LINUX=, +it skips that part of the build and just produces a root filesystem directory.)

+ +

The CROSS= shortcut expects a "ccc" symlink in the toybox source directory +pointing at a directory full of cross compilers. The ones I test this with are built from the musl-libc maintainer's musl-cross-make project, built by running toybox's scripts/mcm-buildall.sh in that directory, and then symlink the resulting "ccc" subdirectory into toybox where CROSS= can find them, ala:

-
+
 cd ~
 git clone https://github.com/landley/toybox
 git clone https://github.com/richfelker/musl-cross-make
 cd musl-cross-make
 ../toybox/scripts/mcm-buildall.sh # this takes a while
 ln -s $(realpath ccc) ../toybox/ccc
-

+
+ +

If you don't want to do that, you can download prebuilt binary versions (from Zach van Rijn's site) and +just extract them into a "ccc" subdirectory under the toybox source.

+ +

Once you've installed the cross compilers, "make root CROSS=help" +should list all the available cross compilers it recognizes under ccc, +something like:

+ +

+aarch64 armv4l armv5l armv7l armv7m armv7r i486 i686 m68k microblaze mips mips64 mipsel powerpc powerpc64 powerpc64le s390x sh2eb sh4 x32 x86_64 +

+ -

An unknown CROSS= should list all the available cross compilers under -ccc. After the above musl-cross-make build and install, -"make root CROSS=help" should say something like: -aarch64 armv4l armv5l armv7l armv7m armv7r i486 i686 m68k microblaze mips mips64 mipsel powerpc powerpc64 powerpc64le s390x sh2eb sh4 x32 x86_64. (A long time ago I tried to explain what some of these architectures were.)

@@ -388,17 +464,20 @@ give a path to them on the command line. (No, I'm not merging more package build scripts, I learned that lesson long ago. But if you want to write your own, feel free.)

-

(Note: if you don't have a .config it'll make defconfig and -add CONFIG_SH and CONFIG_ROUTE to it. If you already have a .config that +

(Note: currently mkroot.sh cheats. If you don't have a .config it'll +make defconfig and add CONFIG_SH and CONFIG_ROUTE to it, because the new +root filesystem kinda needs those commands to function properly. If you already +have a .config that _doesn't_ have CONFIG_SH in it, you won't get a shell prompt or be able to run the init script without a shell. This is currently a problem because sh -and route are still in pending and thus not in defconfig, and "make root" -cheats when it adds them. I'm working on it. tl;dr if make root doesn't work +and route are still in pending and thus not in defconfig, so "make root" +cheats and adds them. I'm working on it. tl;dr if make root doesn't work "rm .config" and run it again, and all this should be fixed up in future when those two commands are promoted out of pending so "make defconfig" would have what you need anyway. It's designed to let yout tweak your config, which is why it uses the .config that's there when there is one, but the default is -currently wrong because it's not quite finished yet.)

+currently wrong because it's not quite finished yet. All this should be +cleaned up in a future release, before 1.0.)

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