| From 690d9163bf4b8563a2682e619f938e6a0443947f Mon Sep 17 00:00:00 2001 |
| From: Paul Burton <paul.burton@mips.com> |
| Date: Tue, 21 Aug 2018 12:12:59 -0700 |
| Subject: MIPS: lib: Provide MIPS64r6 __multi3() for GCC < 7 |
| |
| 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> |
| |
| diff --git a/arch/mips/lib/multi3.c b/arch/mips/lib/multi3.c |
| index 111ad475aa0c..4c2483f410c2 100644 |
| --- 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) |