The instruction_hazard macro made use of the dla pseudo-instruction even
for 32 bit kernels. Although it surrounded that use with ".set mips64rX"
that isn't sufficient to avoid warnings for MIPSr6 CONFIG_32BIT=y
kernels. For example this can be reproduced using maltasmvp_defconfig &
changing only the CPU type to 64r6 (CONFIG_CPU_MIPS64_R6):
CC arch/mips/mm/c-r4k.o
{standard input}: Assembler messages:
{standard input}:4105: Warning: dla used to load 32-bit register;
recommend using la instead
{standard input}:4129: Warning: dla used to load 32-bit register;
recommend using la instead
One seemingly straightforward fix would be to make use of the PTR_LA
macro to emit the appropriate pseudo-instruction, however this would
involve including asm.h which is intended solely for inclusion in
assembly code. When included by C code its definition of various generic
& non-namespaced macros such as LONG, PTR, CAT etc cause numerous build
failures.
Instead fix this by adding a ".set gp=64" directive to inform the
assembler that general purpose registers are 64 bit for the dla
instruction. This is a lie, but no more so than using the dla
instruction to begin with.
Tested with Codescape GNU Tools 2016.05-01 for MIPS IMG Linux, which
includes binutils 2.24.90 & gcc 4.9.2.
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
---
Changes in v3:
- Stop including asm.h, use dla & .set gp=64 instead.
Changes in v2:
- Leave .set <isa> around jr.hb.
- Describe how to reproduce in the commit message.
arch/mips/include/asm/hazards.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/mips/include/asm/hazards.h b/arch/mips/include/asm/hazards.h
index e0fecf206f2c..a3418d064ce1 100644
--- a/arch/mips/include/asm/hazards.h
+++ b/arch/mips/include/asm/hazards.h
@@ -66,10 +66,12 @@ do { \
unsigned long tmp; \
\
__asm__ __volatile__( \
+ " .set push \n" \
" .set "MIPS_ISA_LEVEL" \n" \
+ " .set gp=64 \n" \
" dla %0, 1f \n" \
" jr.hb %0 \n" \
- " .set mips0 \n" \
+ " .set pop \n" \
"1: \n" \
: "=r" (tmp)); \
} while (0)
--
2.12.1
