projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| df1bfe5f GKH |
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 |