Re: [uclibc-ng-devel] [PATCH 00/32] FDPIC ABI for ARM

Am 13.07.2018 um 17:43 schrieb Christophe Lyon <christophe.lyon(a)linaro.org>rg>: Hi, I'd like to ping the whole series. For those anxious about Cortex-M support, I'd prefer to have the current patch series merged, and then add the missing parts for Cortex-M: I have a simple patch to enable the uclibc-ng build for such a target, but then there are further problems with binutils and GCC. So for me it would be much more convenient to have Cortex-A/Cortex-R support merged, so that I can focus later on smaller improvements. Thanks, Christophe > On Wed, 4 Jul 2018 at 17:56, Christophe Lyon <christophe.lyon(a)st.com> wrote: > > Hello, > > This patch series implements the uClibc-ng contribution of the FDPIC > ABI for ARM targets. > > This ABI enables to run Linux on ARM MMU-less cores and supports > shared libraries to reduce the memory footprint. > > Without MMU, text and data segments relative distances are different > from one process to another, hence the need for a dedicated FDPIC > register holding the start address of the data segment. One of the > side effects is that function pointers require two words to be > represented: the address of the code, and the data segment start > address. These two words are designated as "Function Descriptor", > hence the "FD PIC" name. > > On ARM, the FDPIC register is r9 [1], and the target name is > arm-uclinuxfdpiceabi. Note that arm-uclinux exists, but uses another > ABI and the BFLAT file format; it does not support code sharing. > > This work was developed some time ago by STMicroelectronics, and was > presented during Linaro Connect SFO15 (September 2015). You can watch > the discussion and read the slides [2]. > This presentation was related to the toolchain published on github [3], > which is based on binutils-2.22, gcc-4.7, uclibc-0.9.33.2, gdb-7.5.1 > and qemu-2.3.0, and for which pre-built binaries are available [3]. > > The ABI itself is described in details in [1]. > > Our Linux kernel patches have been updated and committed by Nicolas > Pitre (Linaro) in July 2017. They are required so that the loader is > able to handle this new file type. Indeed, the ELF files are tagged > with ELFOSABI_ARM_FDPIC. This new tag has been allocated by ARM, as > well as the new relocations involved. > > The binutils and QEMU patch series have been merged recently. [4][5] > > The GCC patch series has been submitted and is under discussion. [6] > > This patch series consists in the original uClibc-based patches, which > I have rebased and updated for uClibc-ng. Most of them are strictly > related to FDPIC on ARM, while a few others address generic issues. > > Are the uClibc-ng patches OK for inclusion in master? > > Thanks, > > Christophe. > >