docs/development/kernel/getting_started.md - fuchsia - Git at Google

 # Getting started with Zircon

 ## Checking out the Zircon source code

 Note: The Fuchsia source includes Zircon. See Fuchsia's
 [Getting Started](/docs/get-started/README.md) documentation.

 This guide assumes that the Fuchsia project is checked out into `$FUCHSIA_DIR`,
 and `fx` has been configured.

 ## Build Zircon with the default toolchain

 The `fx` command wraps the various tools used to configure, build and interact
 with Fuchsia. The `fx set` command is used to specify the product and the board
 architecture. For example, to set your build target to be Zircon for `arm64`,
 run the following command:

 ```sh
 fx set bringup.arm64
 ```

 Fuchsia uses the concept of
 [products](/docs/development/build/build_system/boards_and_products.md#products) to
 create a collection of build targets. The
 [bringup product](/docs/development/build/build_system/boards_and_products.md#bringup-product)
 is the smallest product with a minimal feature set.

 The following command prints a list of other product configurations:

 ```sh
 fx list-products
 ```

 The following command prints a list of the defined board architectures:

 ```sh
 fx list-boards
 ```

 To execute the build, run the following command:

 ```sh
 fx build
 ```

 The build results are saved in `$FUCHSIA_DIR/out/default`.

 ## Explicitly set the target toolchain

 By default Fuchsia uses the `clang` toolchain. This can be set to `gcc` by using
 the `variants` argument with `fx set`:

 ```sh
 fx set bringup.x64 --variant gcc
 ```

 You can also enable asan by using the variant flag.

 ## Building Zircon for all targets

 You can build for all targets with `fx multi` and using a file that contains all
 the specifications to build. The output for each target is found in
 `$FUCHSIA_DIR/out/<product>.<board>.variant`. An example of a multi build spec
 is <code>[bringup-cq](/tools/devshell/lib/multi-specs/bringup-cq)</code>, which
 approximates what is built for a CQ test.

 Please build for all targets before submitting to ensure builds work on all
 architectures.

 ## QEMU

 You can skip this if you're only testing on actual hardware, but the emulator is
 handy for quick local tests and generally worth having around.

 See [QEMU](/docs/development/debugging/qemu.md) for information on building and
 using QEMU with zircon.

 ## Build Toolchains (Optional)

 If the prebuilt toolchain binaries do not work for you, you can build your own
 from vanilla upstream sources.

 *   The Clang toolchain is used to build Zircon by default or if you build with
     `variants = [ "clang" ]` or `variants = [ "asan" ]`.
 *   The Clang toolchain is also used by default to build host-side code, but any
     C++14-capable toolchain for your build host should work fine.
 *   The GCC toolchain is also available.

 Build one or the other or both, as needed for how you want build Zircon.

 ### GCC Toolchain

 We use GNU `binutils` 2.30[^1] and GCC 8.2, configured with
 `--enable-initfini-array --enable-gold`, and with `--target=x86_64-elf
 --enable-targets=x86_64-pep` for x86-64 or `--target=aarch64-elf` for ARM64.

 For `binutils`, we recommend `--enable-deterministic-archives` but that switch
 is not necessary to get a working build.

 For GCC, it's necessary to pass `MAKEOVERRIDES=USE_GCC_STDINT=provide` on the
 `make` command line. This should ensure that the `stdint.h` GCC installs is one
 that works standalone (`stdint-gcc.h` in the source) rather than one that uses
 `#include_next` and expects another `stdint.h` file installed elsewhere.

 Only the C and C++ language support is required and no target libraries other
 than `libgcc` are required, so you can use various `configure` switches to
 disable other things and make your build of GCC itself go more quickly and use
 less storage, e.g. `--enable-languages=c,c++ --disable-libstdcxx
 --disable-libssp --disable-libquadmath`. See the GCC installation documentation
 for more details.

 You may need various other `configure` switches or other prerequisites to build
 on your particular host system. See the GNU documentation.

 [^1]: The `binutils` 2.30 release has some harmless `make check` failures in the
     `aarch64-elf` and `x86_64-elf` configurations. These are fixed on the
     upstream `binutils-2_30-branch` git branch, which is what we actually
     build. But the 2.30 release version works fine for building Zircon; it
     just has some spurious failures in its own test suite.

 ### Clang/LLVM Toolchain

 We use a trunk snapshot of Clang and update to new snapshots frequently. Any
 build of recent-enough Clang with support for `x86_64` and `aarch64` compiled in
 should work. You'll need a toolchain that also includes the runtime libraries.
 We normally also use the same build of Clang for the host as well as for the
 `*-fuchsia` targets. See [here](/docs/development/build/toolchain.md) for
 details on how we build Clang.

 ### Set up build arguments for toolchains

 If you're using the prebuilt toolchains, you can skip this step, since the build
 will find them automatically.

 Set the build argument that points to where you installed the toolchains:

 ```sh
 fx set bringup.x64 --variant clang --args clang_tool_dir = "<absolute path to>/clang-install/bin/"
 ```

 or for GCC:

 ```sh
 fx set bringup.x64 --variant gcc --args gcc_tool_dir = "<absolute path to>/gcc-install/bin/"
 ```

 Note that `*_tool_dir` should have a trailing slash. If the `clang` or `gcc` in
 your `PATH` works for Zircon, you can just use empty prefixes.

 ## Copying files to and from Zircon

 With local link IPv6 configured you can use `fx cp` to copy files to and from
 the device.

 ## Including Additional Userspace Files

 The Zircon build creates a bootfs image containing necessary userspace
 components for the system to boot (the device manager, some device drivers,
 etc). The kernel is capable of including a second bootfs image, which is provided
 by QEMU or the bootloader as a ramdisk image.

 To create such a bootfs image, use the zbi tool that's generated as part of the
 build. It can assemble a bootfs image for either source directories (in which
 case every file in the specified directory and its subdirectories are included)
 or via a manifest file that specifies, on a file-by-file basis, which files to
 include.

 ```none
 $BUILDDIR/tools/zbi -o extra.bootfs @/path/to/directory

 echo "issue.txt=/etc/issue" > manifest
 echo "etc/hosts=/etc/hosts" >> manifest
 $BUILDDIR/tools/zbi -o extra.bootfs manifest
 ```

 On the booted Zircon system, the files in the bootfs will appear under /boot, so
 in the above manifest example, the "hosts" file would appear at /boot/etc/hosts.

 ## Network Booting {#network-booting}

 Network booting is supported via two mechanisms: Gigaboot and Zirconboot.
 Gigaboot is an EFI based bootloader whereas zirconboot is a mechanism that
 allows a minimal zircon system to serve as a bootloader for zircon.

 On systems that boot via EFI (such as Acer and NUC), either option is viable. On
 other systems, zirconboot may be the only option for network booting.

 ### Via Gigaboot

 The [GigaBoot20x6](/src/firmware/gigaboot) bootloader speaks a simple network
 boot protocol (over IPV6 UDP), which does not require any special host
 configuration or privileged access to use.

 It does this by taking advantage of IPV6 Link Local Addressing and Multicast,
 allowing the device being booted to advertise its bootability and the host to
 find it and send a system image to it.

 If you have a device (for example a Broadwell or Skylake Intel NUC) running
 GigaBoot20x6, first
 [create a USB drive](/docs/development/hardware/usb_setup.md).

 ```none
 $BUILDDIR/tools/bootserver $BUILDDIR/zircon.bin

 # if you have an extra bootfs image (see above):
 $BUILDDIR/tools/bootserver $BUILDDIR/zircon.bin /path/to/extra.bootfs
 ```

 By default bootserver will continue to run and every time it observes a netboot
 beacon it will send the kernel (and bootfs if provided) to that device. If you
 pass the -1 option, bootserver will exit after a successful boot instead.

 ### Via Zirconboot

 Zirconboot is a mechanism that allows a zircon system to serve as the bootloader
 for zircon itself. Zirconboot speaks the same boot protocol as Gigaboot
 described above.

 To use zirconboot, pass the `netsvc.netboot=true` argument to zircon via the
 kernel command line. When zirconboot starts, it will attempt to fetch and boot
 into a zircon system from a bootserver running on the attached host.

 ## Network Log Viewing

 The default build of Zircon includes a network log service that multicasts the
 system log over the link local IPv6 UDP. Please note that this is a quick hack
 and the protocol will certainly change at some point.

 For now, if you're running Zircon on QEMU with the -N flag or running on
 hardware with a supported ethernet interface (ASIX USB Dongle or Intel Ethernet
 on NUC), the loglistener tool will observe logs broadcast over the local link:

 ```none
 $BUILDDIR/tools/loglistener
 ```

 ## Debugging

 For random tips on debugging in the zircon environment see
 [debugging](/docs/development/debugging/tips.md).

 ## Contribute changes

 *   See [CONTRIBUTING.md](/CONTRIBUTING.md#contributing-patches-to-zircon)
	# Getting started with Zircon

	## Checking out the Zircon source code

	Note: The Fuchsia source includes Zircon. See Fuchsia's
	[Getting Started](/docs/get-started/README.md) documentation.

	This guide assumes that the Fuchsia project is checked out into `$FUCHSIA_DIR`,
	and `fx` has been configured.

	## Build Zircon with the default toolchain

	The `fx` command wraps the various tools used to configure, build and interact
	with Fuchsia. The `fx set` command is used to specify the product and the board
	architecture. For example, to set your build target to be Zircon for `arm64`,
	run the following command:

	```sh
	fx set bringup.arm64
	```

	Fuchsia uses the concept of
	[products](/docs/development/build/build_system/boards_and_products.md#products) to
	create a collection of build targets. The
	[bringup product](/docs/development/build/build_system/boards_and_products.md#bringup-product)
	is the smallest product with a minimal feature set.

	The following command prints a list of other product configurations:

	```sh
	fx list-products
	```

	The following command prints a list of the defined board architectures:

	```sh
	fx list-boards
	```

	To execute the build, run the following command:

	```sh
	fx build
	```

	The build results are saved in `$FUCHSIA_DIR/out/default`.

	## Explicitly set the target toolchain

	By default Fuchsia uses the `clang` toolchain. This can be set to `gcc` by using
	the `variants` argument with `fx set`:

	```sh
	fx set bringup.x64 --variant gcc
	```

	You can also enable asan by using the variant flag.

	## Building Zircon for all targets

	You can build for all targets with `fx multi` and using a file that contains all
	the specifications to build. The output for each target is found in
	`$FUCHSIA_DIR/out/<product>.<board>.variant`. An example of a multi build spec
	is <code>[bringup-cq](/tools/devshell/lib/multi-specs/bringup-cq)</code>, which
	approximates what is built for a CQ test.

	Please build for all targets before submitting to ensure builds work on all
	architectures.

	## QEMU

	You can skip this if you're only testing on actual hardware, but the emulator is
	handy for quick local tests and generally worth having around.

	See [QEMU](/docs/development/debugging/qemu.md) for information on building and
	using QEMU with zircon.

	## Build Toolchains (Optional)

	If the prebuilt toolchain binaries do not work for you, you can build your own
	from vanilla upstream sources.

	* The Clang toolchain is used to build Zircon by default or if you build with
	`variants = [ "clang" ]` or `variants = [ "asan" ]`.
	* The Clang toolchain is also used by default to build host-side code, but any
	C++14-capable toolchain for your build host should work fine.
	* The GCC toolchain is also available.

	Build one or the other or both, as needed for how you want build Zircon.

	### GCC Toolchain

	We use GNU `binutils` 2.30[^1] and GCC 8.2, configured with
	`--enable-initfini-array --enable-gold`, and with `--target=x86_64-elf
	--enable-targets=x86_64-pep` for x86-64 or `--target=aarch64-elf` for ARM64.

	For `binutils`, we recommend `--enable-deterministic-archives` but that switch
	is not necessary to get a working build.

	For GCC, it's necessary to pass `MAKEOVERRIDES=USE_GCC_STDINT=provide` on the
	`make` command line. This should ensure that the `stdint.h` GCC installs is one
	that works standalone (`stdint-gcc.h` in the source) rather than one that uses
	`#include_next` and expects another `stdint.h` file installed elsewhere.

	Only the C and C++ language support is required and no target libraries other
	than `libgcc` are required, so you can use various `configure` switches to
	disable other things and make your build of GCC itself go more quickly and use
	less storage, e.g. `--enable-languages=c,c++ --disable-libstdcxx
	--disable-libssp --disable-libquadmath`. See the GCC installation documentation
	for more details.

	You may need various other `configure` switches or other prerequisites to build
	on your particular host system. See the GNU documentation.

	[^1]: The `binutils` 2.30 release has some harmless `make check` failures in the
	`aarch64-elf` and `x86_64-elf` configurations. These are fixed on the
	upstream `binutils-2_30-branch` git branch, which is what we actually
	build. But the 2.30 release version works fine for building Zircon; it
	just has some spurious failures in its own test suite.

	### Clang/LLVM Toolchain

	We use a trunk snapshot of Clang and update to new snapshots frequently. Any
	build of recent-enough Clang with support for `x86_64` and `aarch64` compiled in
	should work. You'll need a toolchain that also includes the runtime libraries.
	We normally also use the same build of Clang for the host as well as for the
	`*-fuchsia` targets. See [here](/docs/development/build/toolchain.md) for
	details on how we build Clang.

	### Set up build arguments for toolchains

	If you're using the prebuilt toolchains, you can skip this step, since the build
	will find them automatically.

	Set the build argument that points to where you installed the toolchains:

	```sh
	fx set bringup.x64 --variant clang --args clang_tool_dir = "<absolute path to>/clang-install/bin/"
	```

	or for GCC:

	```sh
	fx set bringup.x64 --variant gcc --args gcc_tool_dir = "<absolute path to>/gcc-install/bin/"
	```

	Note that `*_tool_dir` should have a trailing slash. If the `clang` or `gcc` in
	your `PATH` works for Zircon, you can just use empty prefixes.

	## Copying files to and from Zircon

	With local link IPv6 configured you can use `fx cp` to copy files to and from
	the device.

	## Including Additional Userspace Files

	The Zircon build creates a bootfs image containing necessary userspace
	components for the system to boot (the device manager, some device drivers,
	etc). The kernel is capable of including a second bootfs image, which is provided
	by QEMU or the bootloader as a ramdisk image.

	To create such a bootfs image, use the zbi tool that's generated as part of the
	build. It can assemble a bootfs image for either source directories (in which
	case every file in the specified directory and its subdirectories are included)
	or via a manifest file that specifies, on a file-by-file basis, which files to
	include.

	```none
	$BUILDDIR/tools/zbi -o extra.bootfs @/path/to/directory

	echo "issue.txt=/etc/issue" > manifest
	echo "etc/hosts=/etc/hosts" >> manifest
	$BUILDDIR/tools/zbi -o extra.bootfs manifest
	```

	On the booted Zircon system, the files in the bootfs will appear under /boot, so
	in the above manifest example, the "hosts" file would appear at /boot/etc/hosts.

	## Network Booting {#network-booting}

	Network booting is supported via two mechanisms: Gigaboot and Zirconboot.
	Gigaboot is an EFI based bootloader whereas zirconboot is a mechanism that
	allows a minimal zircon system to serve as a bootloader for zircon.

	On systems that boot via EFI (such as Acer and NUC), either option is viable. On
	other systems, zirconboot may be the only option for network booting.

	### Via Gigaboot

	The [GigaBoot20x6](/src/firmware/gigaboot) bootloader speaks a simple network
	boot protocol (over IPV6 UDP), which does not require any special host
	configuration or privileged access to use.

	It does this by taking advantage of IPV6 Link Local Addressing and Multicast,
	allowing the device being booted to advertise its bootability and the host to
	find it and send a system image to it.

	If you have a device (for example a Broadwell or Skylake Intel NUC) running
	GigaBoot20x6, first
	[create a USB drive](/docs/development/hardware/usb_setup.md).

	```none
	$BUILDDIR/tools/bootserver $BUILDDIR/zircon.bin

	# if you have an extra bootfs image (see above):
	$BUILDDIR/tools/bootserver $BUILDDIR/zircon.bin /path/to/extra.bootfs
	```

	By default bootserver will continue to run and every time it observes a netboot
	beacon it will send the kernel (and bootfs if provided) to that device. If you
	pass the -1 option, bootserver will exit after a successful boot instead.

	### Via Zirconboot

	Zirconboot is a mechanism that allows a zircon system to serve as the bootloader
	for zircon itself. Zirconboot speaks the same boot protocol as Gigaboot
	described above.

	To use zirconboot, pass the `netsvc.netboot=true` argument to zircon via the
	kernel command line. When zirconboot starts, it will attempt to fetch and boot
	into a zircon system from a bootserver running on the attached host.

	## Network Log Viewing

	The default build of Zircon includes a network log service that multicasts the
	system log over the link local IPv6 UDP. Please note that this is a quick hack
	and the protocol will certainly change at some point.

	For now, if you're running Zircon on QEMU with the -N flag or running on
	hardware with a supported ethernet interface (ASIX USB Dongle or Intel Ethernet
	on NUC), the loglistener tool will observe logs broadcast over the local link:

	```none
	$BUILDDIR/tools/loglistener
	```

	## Debugging

	For random tips on debugging in the zircon environment see
	[debugging](/docs/development/debugging/tips.md).

	## Contribute changes

	* See [CONTRIBUTING.md](/CONTRIBUTING.md#contributing-patches-to-zircon)