commit c87bf431448b404a6ef5fbabd74c0e3e42157a7f upstream.

Enabling CONFIG_GCOV_PROFILE_ALL produces us a lot of warnings like

lib/lz4/lz4hc_compress.c: In function 'lz4_compresshcctx':
lib/lz4/lz4hc_compress.c:514:1: warning: the frame size of 1504 bytes is larger than 1024 bytes [-Wframe-larger-than=]

After some investigation, I found that this behavior started with gcc-4.9,
and opened https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69702.
A suggested workaround for it is to use the -fno-tree-loop-im
flag that turns off one of the optimization stages in gcc, so the
code runs a little slower but does not use excessive amounts
of stack.

We could make this conditional on the gcc version, but I could not
find an easy way to do this in Kbuild and the benefit would be
fairly small, given that most of the gcc version in production are
affected now.

I'm marking this for 'stable' backports because it addresses a bug
with code generation in gcc that exists in all kernel versions
with the affected gcc releases.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit c9c6837d39311b0cc14cdbe7c18e815ab44aefb1 upstream.

gcc-6 started warning by default about variables that are not
used anywhere and that are marked 'const', generating many
false positives in an allmodconfig build, e.g.:

arch/arm/mach-davinci/board-da830-evm.c:282:20: warning: 'da830_evm_emif25_pins' defined but not used [-Wunused-const-variable=]
arch/arm/plat-omap/dmtimer.c:958:34: warning: 'omap_timer_match' defined but not used [-Wunused-const-variable=]
drivers/bluetooth/hci_bcm.c:625:39: warning: 'acpi_bcm_default_gpios' defined but not used [-Wunused-const-variable=]
drivers/char/hw_random/omap-rng.c:92:18: warning: 'reg_map_omap4' defined but not used [-Wunused-const-variable=]
drivers/devfreq/exynos/exynos5_bus.c:381:32: warning: 'exynos5_busfreq_int_pm' defined but not used [-Wunused-const-variable=]
drivers/dma/mv_xor.c:1139:34: warning: 'mv_xor_dt_ids' defined but not used [-Wunused-const-variable=]

This is similar to the existing -Wunused-but-set-variable warning
that was added in an earlier release and that we disable by default
now and only enable when W=1 is set, so it makes sense to do
the same here. Once we have eliminated the majority of the
warnings for both, we can put them back into the default list.

We probably want this in backport kernels as well, to allow building
them with gcc-6 without introducing extra warnings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull objtool fixes from Ingo Molnar:
 "A handful of objtool fixes: two improvements to how warnings are
  printed plus a false positive warning fix, and build environment fix"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Fix Makefile to properly see if libelf is supported
  objtool: Detect falling through to the next function
  objtool: Add workaround for GCC switch jump table bug

When doing a make allmodconfig, I hit the following compile error:

  In file included from builtin-check.c:32:0:
  elf.h:22:18: fatal error: gelf.h: No such file or directory
  compilation terminated.
  ...

Digging into it, it appears that the $(shell ..) command in the Makefile does
not give the proper result when it fails to find -lelf, and continues to
compile objtool.

Instead, use the "try-run" makefile macro to perform the test. This gives a
proper result for both cases.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Fixes: 442f04c34a1a4 ("objtool: Add tool to perform compile-time stack metadata validation")
Link: http://lkml.kernel.org/r/20160420153234.GA24032@home.goodmis.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>