Commit-ID: 8c3641e957a948f41f0174290096ed7a3b95e703 Gitweb: http://git.kernel.org/tip/8c3641e957a948f41f0174290096ed7a3b95e703 Author: Dave Hansen <dave.han...@linux.intel.com> AuthorDate: Sun, 7 Jun 2015 11:37:02 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 9 Jun 2015 12:24:31 +0200
x86/mpx: Introduce a boot-time disable flag MPX has the _potential_ to cause some issues. Say part of your init system tried to protect one of its components from buffer overflows with MPX. If there were a false positive, it's possible that MPX could keep a system from booting. MPX could also potentially cause performance issues since it is present in hot paths like the unmap path. Allow it to be disabled at boot time. Signed-off-by: Dave Hansen <dave.han...@linux.intel.com> Reviewed-by: Thomas Gleixner <t...@linutronix.de Cc: Andrew Morton <a...@linux-foundation.org> Cc: Dave Hansen <d...@sr71.net> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20150607183702.2e8b7...@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- Documentation/kernel-parameters.txt | 4 ++++ arch/x86/kernel/cpu/common.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 61ab162..8b7e5c3 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -937,6 +937,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Enable debug messages at boot time. See Documentation/dynamic-debug-howto.txt for details. + nompx [X86] Disables Intel Memory Protection Extensions. + See Documentation/x86/intel_mpx.txt for more + information about the feature. + eagerfpu= [X86] on enable eager fpu restore off disable eager fpu restore diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 401ccb03..3956858 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -144,6 +144,22 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = { } }; EXPORT_PER_CPU_SYMBOL_GPL(gdt_page); +static int __init x86_mpx_setup(char *s) +{ + /* require an exact match without trailing characters */ + if (strlen(s)) + return 0; + + /* do not emit a message if the feature is not present */ + if (!boot_cpu_has(X86_FEATURE_MPX)) + return 1; + + setup_clear_cpu_cap(X86_FEATURE_MPX); + pr_info("nompx: Intel Memory Protection Extensions (MPX) disabled\n"); + return 1; +} +__setup("nompx", x86_mpx_setup); + #ifdef CONFIG_X86_32 static int cachesize_override = -1; static int disable_x86_serial_nr = 1; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
