| Message ID | 1450768869-13450-1-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | 5008efc83bf85b647aa1cbc44718b1675bbb7444 |
| Headers | show |
On 22 December 2015 at 13:09, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Tue, Dec 22, 2015 at 08:21:09AM +0100, Ard Biesheuvel wrote: >> The PJ4 inline asm sequence to write to cp15 cannot be built in Thumb-2 >> mode, due to the way it performs arithmetic on the program counter, so it >> is built in ARM mode instead. However, building C files in ARM mode under >> CONFIG_THUMB2_KERNEL is problematic, since the instrumentation performed >> by subsystems like ftrace does not expect having to deal with interworking >> branches. >> >> Since the sequence in question is simply a poor man's ISB instruction, >> let's use a straight 'isb' instead when building in Thumb2 mode. Thumb2 >> implies V7, so 'isb' should always be supported in that case. > > I think, given how close Christmas is, and I suspect that the merge > window will be opening shortly afterwards, it'll be better to drop > the change and sort it out in the new year, rather than trying to > rush this in, especially as we're already at the 3rd iteration of > this supposedly simple change. It obviously isn't quite as simple > as it looks. > I agree. Please apply it whenever you feel it is appropriate to do so. Apologies for the trouble _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index af9e59bf3831..3c789496297f 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -73,7 +73,6 @@ obj-$(CONFIG_IWMMXT) += iwmmxt.o obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o obj-$(CONFIG_HW_PERF_EVENTS) += perf_event_xscale.o perf_event_v6.o \ perf_event_v7.o -CFLAGS_pj4-cp0.o := -marm AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt obj-$(CONFIG_ARM_CPU_TOPOLOGY) += topology.o obj-$(CONFIG_VDSO) += vdso.o diff --git a/arch/arm/kernel/pj4-cp0.c b/arch/arm/kernel/pj4-cp0.c index 8153e36b2491..7c9248b74d3f 100644 --- a/arch/arm/kernel/pj4-cp0.c +++ b/arch/arm/kernel/pj4-cp0.c @@ -66,9 +66,13 @@ static void __init pj4_cp_access_write(u32 value) __asm__ __volatile__ ( "mcr p15, 0, %1, c1, c0, 2\n\t" +#ifdef CONFIG_THUMB2_KERNEL + "isb\n\t" +#else "mrc p15, 0, %0, c1, c0, 2\n\t" "mov %0, %0\n\t" "sub pc, pc, #4\n\t" +#endif : "=r" (temp) : "r" (value)); }