x86: Require exact match for 'noxsave' command line option
authorDave Hansen <dave.hansen@linux.intel.com>
Tue, 11 Nov 2014 22:01:33 +0000 (14:01 -0800)
committerThomas Gleixner <tglx@linutronix.de>
Sun, 16 Nov 2014 11:13:16 +0000 (12:13 +0100)
commit2cd3949f702692cf4c5d05b463f19cd706a92dd3
tree43142a52795b60abcb84bcbad1031bdc27eaf53d
parent0cafa3e714fa34af100c575ada31d52caea20957
x86: Require exact match for 'noxsave' command line option

We have some very similarly named command-line options:

arch/x86/kernel/cpu/common.c:__setup("noxsave", x86_xsave_setup);
arch/x86/kernel/cpu/common.c:__setup("noxsaveopt", x86_xsaveopt_setup);
arch/x86/kernel/cpu/common.c:__setup("noxsaves", x86_xsaves_setup);

__setup() is designed to match options that take arguments, like
"foo=bar" where you would have:

__setup("foo", x86_foo_func...);

The problem is that "noxsave" actually _matches_ "noxsaves" in
the same way that "foo" matches "foo=bar".  If you boot an old
kernel that does not know about "noxsaves" with "noxsaves" on the
command line, it will interpret the argument as "noxsave", which
is not what you want at all.

This makes the "noxsave" handler only return success when it finds
an *exact* match.

[ tglx: We really need to make __setup() more robust. ]

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: x86@kernel.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20141111220133.FE053984@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/kernel/cpu/common.c