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Paul Burton 16fd20aa98 kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 
When building using GCC 4.7 or older, -ffunction-sections & the -pg flag
used by ftrace are incompatible. This causes warnings or build failures
(where -Werror applies) such as the following:

  arch/mips/generic/init.c:
    error: -ffunction-sections disabled; it makes profiling impossible

This used to be taken into account by the ordering of calls to cc-option
from within the top-level Makefile, which was introduced by commit
90ad4052e8 ("kbuild: avoid conflict between -ffunction-sections and
-pg on gcc-4.7"). Unfortunately this was broken when the
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION cc-option check was moved to
Kconfig in commit e85d1d65cd ("kbuild: test dead code/data elimination
support in Kconfig"), because the flags used by this check no longer
include -pg.

Fix this by not allowing CONFIG_LD_DEAD_CODE_DATA_ELIMINATION to be
enabled at the same time as ftrace/CONFIG_FUNCTION_TRACER when building
using GCC 4.7 or older.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: e85d1d65cd ("kbuild: test dead code/data elimination support in Kconfig")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-01-14 10:37:09 +09:00
..
calibrate.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
do_mounts.c vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled 2018-12-20 16:32:56 +00:00
do_mounts.h fs: add do_mknodat() helper and ksys_mknod() wrapper; remove in-kernel calls to syscall 2018-04-02 20:15:56 +02:00
do_mounts_initrd.c Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-01-05 13:25:58 -08:00
do_mounts_md.c init/: remove ineffective sparse disabling 2018-08-22 10:52:49 -07:00
do_mounts_rd.c init/: remove ineffective sparse disabling 2018-08-22 10:52:49 -07:00
init_task.c signal: Don't restart fork when signals come in. 2018-08-09 13:07:01 -05:00
initramfs.c initramfs: cleanup incomplete rootfs 2019-01-04 13:13:47 -08:00
Kconfig kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 2019-01-14 10:37:09 +09:00
main.c fork: fix some -Wmissing-prototypes warnings 2019-01-04 13:13:47 -08:00
Makefile Construct init thread stack in the linker script rather than by union 2018-01-09 23:21:02 +00:00
noinitramfs.c fs: add do_mknodat() helper and ksys_mknod() wrapper; remove in-kernel calls to syscall 2018-04-02 20:15:56 +02:00
version.c kbuild: Add build salt to the kernel and modules 2018-07-18 01:18:05 +09:00