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diff --git a/documentation/dev-manual/x32-psabi.rst b/documentation/dev-manual/x32-psabi.rst new file mode 100644 index 0000000000..92b1f96fa4 --- /dev/null +++ b/documentation/dev-manual/x32-psabi.rst @@ -0,0 +1,54 @@ +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK + +Using x32 psABI +*************** + +x32 processor-specific Application Binary Interface (`x32 +psABI <https://software.intel.com/en-us/node/628948>`__) is a native +32-bit processor-specific ABI for Intel 64 (x86-64) architectures. An +ABI defines the calling conventions between functions in a processing +environment. The interface determines what registers are used and what +the sizes are for various C data types. + +Some processing environments prefer using 32-bit applications even when +running on Intel 64-bit platforms. Consider the i386 psABI, which is a +very old 32-bit ABI for Intel 64-bit platforms. The i386 psABI does not +provide efficient use and access of the Intel 64-bit processor +resources, leaving the system underutilized. Now consider the x86_64 +psABI. This ABI is newer and uses 64-bits for data sizes and program +pointers. The extra bits increase the footprint size of the programs, +libraries, and also increases the memory and file system size +requirements. Executing under the x32 psABI enables user programs to +utilize CPU and system resources more efficiently while keeping the +memory footprint of the applications low. Extra bits are used for +registers but not for addressing mechanisms. + +The Yocto Project supports the final specifications of x32 psABI as +follows: + +- You can create packages and images in x32 psABI format on x86_64 + architecture targets. + +- You can successfully build recipes with the x32 toolchain. + +- You can create and boot ``core-image-minimal`` and + ``core-image-sato`` images. + +- There is RPM Package Manager (RPM) support for x32 binaries. + +- There is support for large images. + +To use the x32 psABI, you need to edit your ``conf/local.conf`` +configuration file as follows:: + + MACHINE = "qemux86-64" + DEFAULTTUNE = "x86-64-x32" + baselib = "${@d.getVar('BASE_LIB:tune-' + (d.getVar('DEFAULTTUNE') \ + or 'INVALID')) or 'lib'}" + +Once you have set +up your configuration file, use BitBake to build an image that supports +the x32 psABI. Here is an example:: + + $ bitbake core-image-sato + |