3fc24ef32d
The 32-bit ARM kernel implements fixups on behalf of user space when using LDM/STM or LDRD/STRD instructions on addresses that are not 32-bit aligned. This is not something that is supported by the architecture, but was done anyway to increase compatibility with user space software, which mostly targeted x86 at the time and did not care about aligned accesses. This feature is one of the remaining impediments to being able to switch to 64-bit kernels on 64-bit capable hardware running 32-bit user space, so let's implement it for the arm64 compat layer as well. Note that the intent is to implement the exact same handling of misaligned multi-word loads and stores as the 32-bit kernel does, including what appears to be missing support for user space programs that rely on SETEND to switch to a different byte order and back. Also, like the 32-bit ARM version, we rely on the faulting address reported by the CPU to infer the memory address, instead of decoding the instruction fully to obtain this information. This implementation is taken from the 32-bit ARM tree, with all pieces removed that deal with instructions other than LDRD/STRD and LDM/STM, or that deal with alignment exceptions taken in kernel mode. Cc: debian-arm@lists.debian.org Cc: Vagrant Cascadian <vagrant@debian.org> Cc: Riku Voipio <riku.voipio@iki.fi> Cc: Steve McIntyre <steve@einval.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20220701135322.3025321-1-ardb@kernel.org [catalin.marinas@arm.com: change the option to 'default n'] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> |
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| boot | ||
| configs | ||
| crypto | ||
| hyperv | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| tools | ||
| xen | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.debug | ||
| Kconfig.platforms | ||
| Makefile | ||