queue-4.19/m68k-add-ffreestanding-to-cflags.patch

   1 From 28713169d879b67be2ef2f84dcf54905de238294 Mon Sep 17 00:00:00 2001
   2 From: Finn Thain <fthain@telegraphics.com.au>
   3 Date: Wed, 16 Jan 2019 16:23:24 +1100
   4 Subject: m68k: Add -ffreestanding to CFLAGS
   5
   6 From: Finn Thain <fthain@telegraphics.com.au>
   7
   8 commit 28713169d879b67be2ef2f84dcf54905de238294 upstream.
   9
  10 This patch fixes a build failure when using GCC 8.1:
  11
  12 /usr/bin/ld: block/partitions/ldm.o: in function `ldm_parse_tocblock':
  13 block/partitions/ldm.c:153: undefined reference to `strcmp'
  14
  15 This is caused by a new optimization which effectively replaces a
  16 strncmp() call with a strcmp() call. This affects a number of strncmp()
  17 call sites in the kernel.
  18
  19 The entire class of optimizations is avoided with -fno-builtin, which
  20 gets enabled by -ffreestanding. This may avoid possible future build
  21 failures in case new optimizations appear in future compilers.
  22
  23 I haven't done any performance measurements with this patch but I did
  24 count the function calls in a defconfig build. For example, there are now
  25 23 more sprintf() calls and 39 fewer strcpy() calls. The effect on the
  26 other libc functions is smaller.
  27
  28 If this harms performance we can tackle that regression by optimizing
  29 the call sites, ideally using semantic patches. That way, clang and ICC
  30 builds might benfit too.
  31
  32 Cc: stable@vger.kernel.org
  33 Reference: https://marc.info/?l=linux-m68k&m=154514816222244&w=2
  34 Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
  35 Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
  36 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  37
  38 ---
  39  arch/m68k/Makefile |    5 ++++-
  40  1 file changed, 4 insertions(+), 1 deletion(-)
  41
  42 --- a/arch/m68k/Makefile
  43 +++ b/arch/m68k/Makefile
  44 @@ -58,7 +58,10 @@ cpuflags-$(CONFIG_M5206e)    := $(call cc-o
  45  cpuflags-$(CONFIG_M5206)       := $(call cc-option,-mcpu=5206,-m5200)
  46
  47  KBUILD_AFLAGS += $(cpuflags-y)
  48 -KBUILD_CFLAGS += $(cpuflags-y) -pipe
  49 +KBUILD_CFLAGS += $(cpuflags-y)
  50 +
  51 +KBUILD_CFLAGS += -pipe -ffreestanding
  52 +
  53  ifdef CONFIG_MMU
  54  # without -fno-strength-reduce the 53c7xx.c driver fails ;-(
  55  KBUILD_CFLAGS += -fno-strength-reduce -ffixed-a2