From: Dave Hansen <dave@sr71.net>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, tglx@linutronix.de, Dave Hansen <dave@sr71.net>,
dave.hansen@linux.intel.com
Subject: [PATCH 07/16] x86, mpx: boot-time disable
Date: Tue, 31 Mar 2015 17:46:32 -0700 [thread overview]
Message-ID: <20150401004632.AF6AE44E@viggo.jf.intel.com> (raw)
In-Reply-To: <20150401004623.894DF37A@viggo.jf.intel.com>
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 2015-03-31 16:41:58.026360484 -0700
+++ b/arch/x86/kernel/cpu/common.c 2015-03-31 16:41:58.032360755 -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 2015-03-31 16:41:58.029360619 -0700
+++ b/Documentation/kernel-parameters.txt 2015-03-31 16:41:58.033360800 -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
_
next prev parent reply other threads:[~2015-04-01 0:48 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-01 0:46 [PATCH 00/16] x86, mpx updates for 4.1 (take 4) Dave Hansen
2015-04-01 0:46 ` [PATCH 01/16] x86, fpu: wrap get_xsave_addr() to make it safer Dave Hansen
2015-04-22 10:40 ` Borislav Petkov
2015-04-22 13:16 ` Oleg Nesterov
2015-04-22 13:31 ` Borislav Petkov
2015-04-22 14:56 ` Dave Hansen
2015-04-22 15:17 ` Thomas Gleixner
2015-04-22 15:21 ` Borislav Petkov
2015-04-22 15:26 ` Thomas Gleixner
2015-04-22 16:02 ` Dave Hansen
2015-04-22 15:32 ` Oleg Nesterov
2015-04-22 15:58 ` Borislav Petkov
2015-04-01 0:46 ` [PATCH 02/16] x86, mpx: use new tsk_get_xsave_addr() Dave Hansen
2015-04-01 0:46 ` [PATCH 03/16] x86, mpx: trace #BR exceptions Dave Hansen
2015-04-01 0:46 ` [PATCH 04/16] x86, mpx: trace entry to bounds exception paths Dave Hansen
2015-04-01 0:46 ` [PATCH 05/16] x86, mpx: trace ranged MPX operations Dave Hansen
2015-04-01 0:46 ` [PATCH 06/16] x86, mpx: trace allocation of new bounds tables Dave Hansen
2015-04-01 0:46 ` Dave Hansen [this message]
2015-04-01 0:46 ` [PATCH 08/16] x86: make is_64bit_mm() widely available Dave Hansen
2015-04-01 0:46 ` [PATCH 09/16] x86: make __VIRTUAL_MASK safe to use on 32 bit Dave Hansen
2015-04-01 0:46 ` [PATCH 10/16] x86, mpx: we do not allocate the bounds directory Dave Hansen
2015-04-01 0:46 ` [PATCH 11/16] x86, mpx: remove redundant MPX_BNDCFG_ADDR_MASK Dave Hansen
2015-04-01 0:46 ` [PATCH 12/16] x86, mpx: Add temporary variable to reduce masking Dave Hansen
2015-04-01 0:46 ` [PATCH 13/16] x86, mpx: new directory entry to addr helper Dave Hansen
2015-04-01 0:46 ` [PATCH 14/16] x86, mpx: do 32-bit-only cmpxchg for 32-bit apps Dave Hansen
2015-04-01 0:46 ` [PATCH 15/16] x86, mpx: support 32-bit binaries on 64-bit kernel Dave Hansen
2015-04-01 0:46 ` [PATCH 16/16] x86, mpx: allow mixed binaries again Dave Hansen
2015-04-21 15:39 ` [PATCH 00/16] x86, mpx updates for 4.1 (take 4) Dave Hansen
2015-04-22 10:49 ` Borislav Petkov
2015-04-22 14:43 ` Dave Hansen
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