Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Mon, 06 Nov 2017 23:03:02 +0000 | Subject | [PATCH 3.16 273/294] ARM: 8452/3: PJ4: make coprocessor access sequences buildable in Thumb2 mode |
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3.16.50-rc1 review patch. If anyone has any objections, please let me know.
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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
commit 5008efc83bf85b647aa1cbc44718b1675bbb7444 upstream.
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.
Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- arch/arm/kernel/Makefile | 1 - arch/arm/kernel/pj4-cp0.c | 4 ++++ 2 files changed, 4 insertions(+), 1 deletion(-)
--- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -84,7 +84,6 @@ obj-$(CONFIG_CPU_PJ4B) += pj4-cp0.o obj-$(CONFIG_IWMMXT) += iwmmxt.o obj-$(CONFIG_PERF_EVENTS) += perf_regs.o obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o perf_event_cpu.o -CFLAGS_pj4-cp0.o := -marm AFLAGS_iwmmxt.o := -Wa,-mcpu=iwmmxt obj-$(CONFIG_ARM_CPU_TOPOLOGY) += topology.o --- 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(u __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)); }
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