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authorPaul Burton <paul.burton@mips.com>2018-08-21 12:12:59 -0700
committerPaul Burton <paul.burton@mips.com>2018-08-21 12:14:11 -0700
commit690d9163bf4b8563a2682e619f938e6a0443947f (patch)
tree0278ecd283fa77301a51839d164dc350f6dd4599 /arch/mips/lib
parent906d441febc0de974b2a6ef848a8f058f3bfada3 (diff)
downloadlinux-690d9163bf4b8563a2682e619f938e6a0443947f.tar.gz
MIPS: lib: Provide MIPS64r6 __multi3() for GCC < 7
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+
Diffstat (limited to 'arch/mips/lib')
-rw-r--r--arch/mips/lib/multi3.c6
1 files changed, 3 insertions, 3 deletions
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)