Hello, This patch series implements the QEMU 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 segment 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 [3]. 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 [1]. This presentation was related to the toolchain published on github [2], 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 [2]. The ABI itself is described in details in [3]. 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. This patch series has been rebased on top of QEMU from 2018-03-28. I have also rebased the GCC patch series, but it is still WIP as cleanup is still needed before I can request a review. It can be useful to build a preview toolchain though, so my WIP branch is available at [4]. To build such a toolchain, you'd also need to use my uClibc branch [5]. I am currently working on updating the patches for the other toolchain components, and will upstream them soon. This includes gcc, uclibc, and gdb. This series provides support for ARM v7 and later architectures and has been used to run the GCC tests on arm-linux-gnueabi without regression, as well as arm-linux-uclibceabi. Are the QEMU patches OK for inclusion in master? Thanks, Christophe. [1] http://connect.linaro.org/resource/sfo15/sfo15-406-arm-fdpic-toolset-kernel-libraries-for-cortex-m-cortex-r-mmuless-cores/ [2] https://github.com/mickael-guene/fdpic_manifest [3] https://github.com/mickael-guene/fdpic_doc/blob/master/abi.txt [4] https://git.linaro.org/people/christophe.lyon/gcc.git/log/?h=fdpic-upstream [5] https://git.linaro.org/people/christophe.lyon/uclibc.git/log/?h=uClibc-0.9.33.2-fdpic-upstream Christophe Lyon (4): linux-user: ARM-FDPIC: Add configure option to support loading of FDPIC binaries linux-user: ARM-FDPIC: Add support of FDPIC for ARM. linux-user: ARM-FDPIC: Add support for signals for FDPIC targets linux-user: ARM-FDPIC: Add arm get tls syscall support configure | 10 +++++ include/elf.h | 1 + linux-user/arm/target_syscall.h | 1 + linux-user/elfload.c | 35 ++++++++++++++++ linux-user/main.c | 8 ++++ linux-user/qemu.h | 3 ++ linux-user/signal.c | 91 +++++++++++++++++++++++++++++++++++++---- target/arm/cpu.h | 6 +++ 8 files changed, 147 insertions(+), 8 deletions(-) -- 2.6.3
