On 16 September 2018 at 16:53, Richard Henderson <richard.hender...@linaro.org> wrote: > Ah, I did not know about SWP_EMULATE. It appears to be > specific to armv7+ (though we don't support the pre-v4 > cpus for which it might otherwise be relevant). > > It does appear that HWCAP_SWP is advertised anyway: > > mm/proc-v7.S: .long HWCAP_SWP | HWCAP_HALF | HWCAP_THUMB | HWCAP_FAST_MULT
I just discovered that that is overridden by arch/arm/kernel/setup.c:elf_hwcap_fixup(), which looks at the ID registers and suppresses HWCAP_SWP if LDREX/STREX and LDREXB/STREXB are supported. (Compat 32-bit support in a 64-bit kernel never advertises HWCAP_SWP.) thanks -- PMM
