1 Native Client 2 ============= 3 4 This document outlines the basics of building and developing the Go runtime and 5 programs in the Native Client (NaCl) environment. 6 7 Go 1.3 supports three architectures 8 9 * nacl/386 which is standard 386. 10 * nacl/amd64p32 which is a 64 bit architecture, where the address space is 11 limited to a 4gb window. 12 * nacl/arm which is 32-bit ARMv7A architecture with 1GB address space. 13 14 For background it is recommended that you read https://golang.org/s/go13nacl. 15 16 Prerequisites 17 ------------- 18 19 Native Client programs are executed inside a sandbox, the NaCl runtime. This 20 runtime must be installed before you can use NaCl programs. 21 22 The NaCl distribution comes with an installer which ensures you have access to 23 the latest version of the runtime. The version tracks the Chrome numbering 24 scheme. 25 26 # Download NaCl 27 28 Download nacl_sdk.zip file from 29 https://developers.google.com/native-client/dev/sdk/download 30 and unpack it. I chose /opt/nacl_sdk. 31 32 # Update 33 34 The zip file contains a small skeleton that can be used to download the correct 35 sdk. These are released every 6-8 weeks, in line with Chrome releases. 36 37 % cd /opt/nacl_sdk 38 % ./naclsdk update 39 40 At this time pepper_40 is the stable version. The NaCl port needs at least pepper_39 41 to work. If naclsdk downloads a later version, please adjust accordingly. 42 43 The cmd/go helper scripts expect that the loaders sel_ldr_{x86_{32,64},arm} and 44 nacl_helper_bootstrap_arm are in your path. I find it easiest to make a symlink 45 from the NaCl distribution to my $GOPATH/bin directory. 46 47 % ln -nfs /opt/nacl_sdk/pepper_39/tools/sel_ldr_x86_32 $GOPATH/bin/sel_ldr_x86_32 48 % ln -nfs /opt/nacl_sdk/pepper_39/tools/sel_ldr_x86_64 $GOPATH/bin/sel_ldr_x86_64 49 % ln -nfs /opt/nacl_sdk/pepper_39/tools/sel_ldr_arm $GOPATH/bin/sel_ldr_arm 50 51 Additionally, for NaCl/ARM only: 52 53 % ln -nfs /opt/nacl_sdk/pepper_39/tools/nacl_helper_bootstrap_arm $GOPATH/bin/nacl_helper_bootstrap_arm 54 55 Support scripts 56 --------------- 57 58 Symlink the two scripts in this directory into your $PATH, just as you did with 59 NaCl sdk above. 60 61 % ln -nfs $GOROOT/misc/nacl/go_nacl_amd64p32_exec $GOPATH/bin/go_nacl_amd64p32_exec 62 % ln -nfs $GOROOT/misc/nacl/go_nacl_386_exec $GOPATH/bin/go_nacl_386_exec 63 % ln -nfs $GOROOT/misc/nacl/go_nacl_arm_exec $GOPATH/bin/go_nacl_arm_exec 64 65 Building and testing 66 -------------------- 67 68 Building for NaCl is similar to cross compiling for other platforms. However, 69 as it is not possible to ever build in a `native` NaCl environment, the cmd/go 70 tool has been enhanced to allow the full build, all.bash, to be executed, 71 rather than just the compile stage, make.bash. 72 73 The cmd/go tool knows that if GOOS is set to `nacl` it should not try to 74 execute any binaries itself. Instead it passes their execution to a support 75 script which sets up a Native Client environment and invokes the NaCl sandbox. 76 77 The script's name has a special format, go_$GOOS_$GOARCH_exec, so cmd/go can 78 find it. 79 80 In short, if the support scripts are in place, the cmd/go tool can be used as 81 per normal. 82 83 # Build and test Go for NaCl 84 85 NaCl does not permit direct file system access. Instead, package syscall 86 provides a simulated file system served by in-memory data. The script 87 nacltest.bash is the NaCl equivalent of all.bash. It builds NaCl with an 88 in-memory file system containing files needed for tests, and then it runs the 89 tests. 90 91 % cd go/src 92 % env GOARCH=amd64p32 ./nacltest.bash 93 94 Debugging 95 --------- 96 97 Assuming that you have built nacl/amd64p32 binary ./mybin and can run as: 98 99 % sel_ldr_x86_64 -l /dev/null -S -e ./mybin 100 101 Create the nacl manifest file mybin.manifest with the following contents: 102 103 { "program": { "x86-64": { "url": "mybin" } } } 104 105 url is the path to the binary relative to the manifest file. 106 Then, run the program as: 107 108 % sel_ldr_x86_64 -g -l /dev/null -S -e ./mybin 109 110 The -g flag instructs the loader to stop at startup. Then, in another console: 111 112 % /opt/nacl_sdk/pepper_39/toolchain/linux_x86_glibc/bin/x86_64-nacl-gdb 113 % nacl-manifest mybin.manifest 114 % target remote :4014 115 116 If you see that the program is stopped in _rt0_amd64p32_nacl, then symbols are 117 loaded successfully and you can type 'c' to start the program. 118 Next time you can automate it as: 119 120 % /opt/nacl_sdk/pepper_39/toolchain/linux_x86_glibc/bin/x86_64-nacl-gdb \ 121 -ex 'nacl-manifest mybin.manifest' -ex 'target remote :4014' 122
