Commit d07d4e8b authored by Paul Burton's avatar Paul Burton Committed by Greg Kroah-Hartman
Browse files

MIPS: lib: Provide MIPS64r6 __multi3() for GCC < 7

commit 690d9163


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: default avatarPaul Burton <>
Reported-by: default avatarVladimir Kondratiev <>
Fixes: ebabcf17 ("MIPS: Implement __multi3 for GCC7 MIPS64r6 builds")

Cc: James Hogan <>
Cc: Ralf Baechle <>
Cc: # 4.15+
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 8f55e1f5
......@@ -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
#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)
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