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68 lines
3.4 KiB
Plaintext
68 lines
3.4 KiB
Plaintext
Native Client
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=============
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This document outlines the basics of building and developing the Go runtime and programs in the Native Client (NaCl) environment.
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Go 1.3 supports three architectures
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* nacl/386 which is standard 386.
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* nacl/amd64p32 which is a 64 bit architecture, where the address space is limited to a 4gb window.
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* nacl/arm which is 32-bit ARMv7A architecture with 1GB address space.
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For background it is recommended that you read http://golang.org/s/go13nacl.
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Prerequisites
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-------------
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Native Client programs are executed inside a sandbox, the NaCl runtime. This runtime must be installed before you can use NaCl programs.
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The NaCl distribution comes with an installer which ensures you have access to the latest version of the runtime. The version tracks the Chrome numbering scheme.
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# Download NaCl
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Download nacl_sdk.zip file from https://developers.google.com/native-client/dev/sdk/download, and unpack it. I chose /opt/nacl_sdk
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# Update
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The zip file contains a small skeleton that can be used to download the correct sdk. These are released every 6-8 weeks, in line with Chrome releases.
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% cd /opt/nacl_sdk
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% ./naclsdk update
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At this time pepper_33 is the stable version. If naclsdk downloads a later version, please adjust accordingly. As of June 2014, only the canary sdk provides support for nacl/arm.
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The cmd/go helper scripts expect that the runtime loaders, sel_ldr_{x86_{32,64},arm} and nacl_helper_bootstrap_arm are in your path. I find it easiest to make a symlink from the NaCl distribution to my $GOPATH/bin directory.
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% ln -nfs /opt/nacl_sdk/pepper_33/tools/sel_ldr_x86_32 $GOPATH/bin/sel_ldr_x86_32
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% ln -nfs /opt/nacl_sdk/pepper_33/tools/sel_ldr_x86_64 $GOPATH/bin/sel_ldr_x86_64
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% ln -nfs /opt/nacl_sdk/pepper_canary/tools/sel_ldr_arm $GOPATH/bin/sel_ldr_arm
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% ln -nfs /opt/nacl_sdk/pepper_canary/tools/nacl_helper_bootstrap_arm $GOPATH/bin/nacl_helper_bootstrap_arm # only required for NaCl/ARM.
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Support scripts
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---------------
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Symlink the two scripts in this directory into your $PATH, just as you did with NaCl sdk above.
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% ln -nfs $GOROOT/go/misc/nacl/go_nacl_amd64p32_exec $GOPATH/bin/go_nacl_amd64p32_exec
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% ln -nfs $GOROOT/go/misc/nacl/go_nacl_386_exec $GOPATH/bin/go_nacl_386_exec
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% ln -nfs $GOROOT/go/misc/nacl/go_nacl_arm_exec $GOPATH/bin/go_nacl_arm_exec
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Building and testing
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--------------------
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Building for NaCl is similar to cross compiling for other platforms. However, as it is not possible to ever build in a `native` NaCl environment, the cmd/go tool has been enhanced to allow the full build, all.bash, to be executed, rather than just the compile stage, make.bash.
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The cmd/go tool knows that if GOOS is set to `nacl` it should not try to execute any binaries itself. Instead it passes their execution to a support script which sets up a Native Client environment and invokes the NaCl sandbox.
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The script's name has a special format, go_$GOOS_$GOARCH_exec, so cmd/go can find it.
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In short, if the support scripts are in place, the cmd/go tool can be used as per normal.
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# Build and test Go for NaCl
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NaCl does not permit direct file system access. Instead, package syscall provides a simulated file system served by in-memory data. The script nacltest.bash is the NaCl equivalent of all.bash. It builds NaCl with an in-memory file system containing files needed for tests, and then it runs the tests.
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% cd go/src
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% env GOARCH=amd64p32 ./nacltest.bash
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