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The popular method to load PRU firmware is through the remoteproc Linux kernel driver. In order to save a few bytes from the firmware, the PRU CRT0 is spared from calling memset for the bss segment [1]. Instead the host loader is supposed to zero out the bss segment. This is important for PRU, which typically has only 8KB for instruction memory. The legacy non-mainline PRU host driver relied on the default behaviour of the kernel core remoteproc [2]. That default is to zero out the loadable memory regions not backed by file storage (i.e. the bss sections). This worked for the libgloss' CRT0. But the PRU loader merged in mainline Linux explicitly changes the default behaviour [3]. It no longer is zeroing out memory regions. Hence the bss sections are not initialized - neither by CRT0, nor by the host loader. This patch fixes the issue by aligning the GNU LD default linker script with the mainline Linux kernel expectation. Since the mainline kernel driver is submitted by the PRU manufacturer itself (Text Instruments), we can consider that as defining the ABI. This change has been tested on Beaglebone AI-64 [4]. Static counter variables in the firmware are now always starting from zero, as expected. There was only one new toolchain test failure in orphan3.d, due to reordering of the output sections. I believe this is a harmless issue. I could not rewrite the PASS criteria to ignore the output section ordering, so I have disabled that test case for PRU. [1] https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=libgloss/pru/crt0.S;h=b3f0d53a93acc372f461007553e7688ca77753c9;hb=HEAD#l40 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/remoteproc/remoteproc_elf_loader.c?h=v6.1#n228 [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/remoteproc/pru_rproc.c?h=v6.1#n641 [4] https://beagleboard.org/ai-64 ld/ChangeLog: * scripttempl/pru.sc (.data): Merge .bss input sections into the .data output section. * testsuite/ld-elf/orphan3.d: Disable for PRU. Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.