Messages in this thread | | | Date | Sun, 17 Sep 2023 12:26:03 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v2] fs: binfmt_elf_efpic: fix personality for ELF-FDPIC |
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On Thu, 7 Sep 2023 11:18:08 +1000 Greg Ungerer <gerg@kernel.org> wrote:
> The elf-fdpic loader hard sets the process personality to either > PER_LINUX_FDPIC for true elf-fdpic binaries or to PER_LINUX for > normal ELF binaries (in this case they would be constant displacement > compiled with -pie for example). The problem with that is that it > will lose any other bits that may be in the ELF header personality > (such as the "bug emulation" bits). > > On the ARM architecture the ADDR_LIMIT_32BIT flag is used to signify > a normal 32bit binary - as opposed to a legacy 26bit address binary. > This matters since start_thread() will set the ARM CPSR register as > required based on this flag. If the elf-fdpic loader loses this bit > the process will be mis-configured and crash out pretty quickly. > > Modify elf-fdpic loader personality setting so that it preserves the > upper three bytes by using the SET_PERSONALITY macro to set it. This > macro in the generic case sets PER_LINUX and preserves the upper bytes. > Architectures can override this for their specific use case, and ARM > does exactly this. > > The problem shows up quite easily running under qemu using the ARM > architecture, but not necessarily on all types of real ARM hardware. > If the underlying ARM processor does not support the legacy 26-bit > addressing mode then everything will work as expected.
I'm thinking
Fixes: 1bde925d23547 ("fs/binfmt_elf_fdpic.c: provide NOMMU loader for regular ELF binaries") Cc: <stable@vger.kernel.org>
?
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