Messages in this thread Patch in this message | | | Subject | [PATCH 08/17] x86, mpx: boot-time disable | From | Dave Hansen <> | Date | Fri, 27 Mar 2015 14:53:05 -0700 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
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.hansen@linux.intel.com> ---
b/Documentation/kernel-parameters.txt | 4 ++++ b/arch/x86/kernel/cpu/common.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+)
diff -puN arch/x86/kernel/cpu/common.c~x86-mpx-disable-boot-time arch/x86/kernel/cpu/common.c --- a/arch/x86/kernel/cpu/common.c~x86-mpx-disable-boot-time 2015-03-27 14:35:06.804853764 -0700 +++ b/arch/x86/kernel/cpu/common.c 2015-03-27 14:35:06.809853989 -0700 @@ -172,6 +172,22 @@ static int __init x86_xsaves_setup(char } __setup("noxsaves", x86_xsaves_setup); +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; diff -puN Documentation/kernel-parameters.txt~x86-mpx-disable-boot-time Documentation/kernel-parameters.txt --- a/Documentation/kernel-parameters.txt~x86-mpx-disable-boot-time 2015-03-27 14:35:06.806853854 -0700 +++ b/Documentation/kernel-parameters.txt 2015-03-27 14:35:06.811854080 -0700 @@ -2340,6 +2340,10 @@ bytes respectively. Such letter suffixes parameter, xsave area per process might occupy more memory on xsaves enabled systems. + 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 _
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