x86, hweight: Fix BUG when booting with CONFIG_GCOV_PROFILE_ALL=y
authorPeter Oberparleiter <oberpar@linux.vnet.ibm.com>
Thu, 6 Feb 2014 14:58:20 +0000 (15:58 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 20 Feb 2014 19:06:11 +0000 (11:06 -0800)
commitf878b94f967e1c6ee0d3c220063db3ff52fe0448
treeb4b7b3d919f2f58e4ba3c8033708c9ed79d0372e
parentf19148c7959cd94e70a32a92d05a19e92d9826e8
x86, hweight: Fix BUG when booting with CONFIG_GCOV_PROFILE_ALL=y

commit 6583327c4dd55acbbf2a6f25e775b28b3abf9a42 upstream.

Commit d61931d89b, "x86: Add optimized popcnt variants" introduced
compile flag -fcall-saved-rdi for lib/hweight.c. When combined with
options -fprofile-arcs and -O2, this flag causes gcc to generate
broken constructor code. As a result, a 64 bit x86 kernel compiled
with CONFIG_GCOV_PROFILE_ALL=y prints message "gcov: could not create
file" and runs into sproadic BUGs during boot.

The gcc people indicate that these kinds of problems are endemic when
using ad hoc calling conventions.  It is therefore best to treat any
file compiled with ad hoc calling conventions as an isolated
environment and avoid things like profiling or coverage analysis,
since those subsystems assume a "normal" calling conventions.

This patch avoids the bug by excluding lib/hweight.o from coverage
profiling.

Reported-by: Meelis Roos <mroos@linux.ee>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/52F3A30C.7050205@linux.vnet.ibm.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
lib/Makefile