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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2015-12-22 08:24:59 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-05-14 13:32:54 +0200
commit3e8c47e9c1ac31b5a299e404ffac163fc9743f31 (patch)
tree1f083fde93c32815428159f2f72fc861216f9182
parent436188eb0447fc5117bba45963c783769c44600e (diff)
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ARM: 8452/3: PJ4: make coprocessor access sequences buildable in Thumb2 mode
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/arm/kernel/Makefile1
-rw-r--r--arch/arm/kernel/pj4-cp0.c4
2 files changed, 4 insertions, 1 deletions
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));
}