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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2015-12-22 08:24:59 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-05-15 09:19:09 +0200
commit94a4e4e467d7a951fcc45e7b49c74eda3e00c7ea (patch)
treec30d5e1f7047a78408784626375b2c1e7b09f7aa
parent90757afa09b88dbec2a348037edaf65d4e1ac5c4 (diff)
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 2ecc7d15bc09..03120e656aea 100644
--- 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
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));
}