4.18-stable review patch. If anyone has any objections, please let me know.
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From: Paul Burton paul.burton@mips.com
commit 690d9163bf4b8563a2682e619f938e6a0443947f upstream.
Some versions of GCC suboptimally generate calls to the __multi3() intrinsic for MIPS64r6 builds, resulting in link failures due to the missing function:
LD vmlinux.o MODPOST vmlinux.o kernel/bpf/verifier.o: In function `kmalloc_array': include/linux/slab.h:631: undefined reference to `__multi3' fs/select.o: In function `kmalloc_array': include/linux/slab.h:631: undefined reference to `__multi3' ...
We already have a workaround for this in which we provide the instrinsic, but we do so selectively for GCC 7 only. Unfortunately the issue occurs with older GCC versions too - it has been observed with both GCC 5.4.0 & GCC 6.4.0.
MIPSr6 support was introduced in GCC 5, so all major GCC versions prior to GCC 8 are affected and we extend our workaround accordingly to all MIPS64r6 builds using GCC versions older than GCC 8.
Signed-off-by: Paul Burton paul.burton@mips.com Reported-by: Vladimir Kondratiev vladimir.kondratiev@intel.com Fixes: ebabcf17bcd7 ("MIPS: Implement __multi3 for GCC7 MIPS64r6 builds") Patchwork: https://patchwork.linux-mips.org/patch/20297/ Cc: James Hogan jhogan@kernel.org Cc: Ralf Baechle ralf@linux-mips.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # 4.15+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/mips/lib/multi3.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/mips/lib/multi3.c +++ b/arch/mips/lib/multi3.c @@ -4,12 +4,12 @@ #include "libgcc.h"
/* - * GCC 7 suboptimally generates __multi3 calls for mips64r6, so for that - * specific case only we'll implement it here. + * GCC 7 & older can suboptimally generate __multi3 calls for mips64r6, so for + * that specific case only we implement that intrinsic here. * * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82981 */ -#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ == 7) +#if defined(CONFIG_64BIT) && defined(CONFIG_CPU_MIPSR6) && (__GNUC__ < 8)
/* multiply 64-bit values, low 64-bits returned */ static inline long long notrace dmulu(long long a, long long b)