* Jamie Lokier <jamie@xxxxxxxxxxxxx> [100622 19:54]: > Tony Lindgren wrote: > > __kuser_get_tls: @ 0xffff0fe0 > > - > > -#if !defined(CONFIG_HAS_TLS_REG) && !defined(CONFIG_TLS_REG_EMUL) > > - ldr r0, [pc, #(16 - 8)] @ TLS stored at 0xffff0ff0 > > -#else > > - mrc p15, 0, r0, c13, c0, 3 @ read TLS register > > -#endif > > + ldr r0, [pc, #(20 - 8)] @ software TLS set in 0xffff0ff4? > > + cmp r0, #0 @ hardware TLS if flag not set > > + mrceq p15, 0, r0, c13, c0, 3 @ read hardware TLS register > > + ldrne r0, [pc, #(12 - 8)] @ software TLS val at 0xffff0ff8 > > usr_ret lr > > - > > - .rep 5 > > - .word 0 @ pad up to __kuser_helper_version > > - .endr > > + .word 0 @ non-zero for software TLS > > + .word 0 @ software TLS value > > It'd be nice not to waste instructions checking for HWCAP_TLS on archs > which definitely don't have it. I guess it doesn't matter elsewhere; > I'd expect this to be a warm path for some programs making extensive > use of TLS (I haven't measured though). OK, but let's try to figure out a way that does not add more ifdef else code as that makes it harder to build support for multiple ARM cores. > As it's only a single instruction, and the code is in a writable page > already (copied at init), how about just patching the instruction > when ELF_HWCAP is set? Yeah that can be done for __kuser_get_tls if it's always writable. But __switch_to is trickier because of the CONFIG_MMU ifdefs there. What if we have optional __switch_to and __kuser_get_tls implementations in the mm/proc-*.S files that get copied over the current locations if implemented? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
