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16fd20aa98
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.