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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
arch ARM: SoC fixes 2019-01-14 10:34:14 +12:00
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Makefile Linux 5.0-rc2 2019-01-14 10:41:12 +12:00
README

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.