arm64: Implement __lshrti3 library function

Commit fb8722735f50 ("arm64: support __int128 on gcc 5+") added support
for the __int128 data type, but this breaks the build in some configurations
where GCC ends up emitting calls to the __lshrti3 helper in libgcc, which
results in a link error:

  kernel/sched/fair.o: In function `__calc_delta':
  fair.c:(.text+0xca0): undefined reference to `__lshrti3'
  kernel/time/timekeeping.o: In function `timekeeping_resume':
  timekeeping.c:(.text+0x3f60): undefined reference to `__lshrti3'
  make: *** [vmlinux] Error 1

Fix the build by providing an implementation of __lshrti3, like we do
already for __ashlti3 and __ashrti3.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/lib/tishift.S b/arch/arm64/lib/tishift.S
index 7236776655edbb1bc544a5feabcdb13cd0db55de..0179a43cc0458282cb602c25a4e0e54a00f5e0d8 100644 (file)
--- a/arch/arm64/lib/tishift.S
+++ b/arch/arm64/lib/tishift.S
@@ -57,3 +57,24 @@ ENTRY(__ashrti3)
        mov     x1, x2
        ret
 ENDPROC(__ashrti3)
+
+ENTRY(__lshrti3)
+       cbz     x2, 1f
+       mov     x3, #64
+       sub     x3, x3, x2
+       cmp     x3, #0
+       b.le    2f
+       lsr     x0, x0, x2
+       lsl     x3, x1, x3
+       lsr     x2, x1, x2
+       orr     x0, x0, x3
+       mov     x1, x2
+1:
+       ret
+2:
+       neg     w0, w3
+       mov     x2, #0
+       lsr     x0, x1, x0
+       mov     x1, x2
+       ret
+ENDPROC(__lshrti3)