diff options
| author | Paul Burton <paul.burton@mips.com> | 2018-08-21 21:12:59 +0200 |
|---|---|---|
| committer | Paul Burton <paul.burton@mips.com> | 2018-08-21 21:14:11 +0200 |
| commit | 690d9163bf4b8563a2682e619f938e6a0443947f (patch) | |
| tree | 0278ecd283fa77301a51839d164dc350f6dd4599 /arch/mips/lib/multi3.c | |
| parent | MIPS: Workaround GCC __builtin_unreachable reordering bug (diff) | |
| download | linux-690d9163bf4b8563a2682e619f938e6a0443947f.tar.xz linux-690d9163bf4b8563a2682e619f938e6a0443947f.zip | |
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/multi3.c')
| -rw-r--r-- | arch/mips/lib/multi3.c | 6 |
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) |