From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Markus T Metzger <markus.t.metzger@intel.com>,
Ravi Shankar <ravi.v.shankar@intel.com>,
"Chang S . Bae" <chang.seok.bae@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH v4 11/13] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit
Date: Wed, 16 Jan 2019 14:48:47 -0800 [thread overview]
Message-ID: <20190116224849.8617-12-chang.seok.bae@intel.com> (raw)
In-Reply-To: <20190116224849.8617-1-chang.seok.bae@intel.com>
From: Andy Lutomirski <luto@kernel.org>
Now that FSGSBASE is fully supported, remove unsafe_fsgsbase, enable
FSGSBASE by default, and add nofsgsbase to disable it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
---
.../admin-guide/kernel-parameters.txt | 3 +-
arch/x86/kernel/cpu/common.c | 35 ++++++++-----------
2 files changed, 15 insertions(+), 23 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 871260e3e832..20ab1ba22a3e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2760,8 +2760,7 @@
no5lvl [X86-64] Disable 5-level paging mode. Forces
kernel to use 4-level paging instead.
- unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be
- replaced with a nofsgsbase flag.
+ nofsgsbase [X86] Disables FSGSBASE instructions.
no_console_suspend
[HW] Never suspend the console
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6e2cba21328f..3d7d4ca1a29e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -365,24 +365,21 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
cr4_clear_bits(X86_CR4_UMIP);
}
-/*
- * Temporary hack: FSGSBASE is unsafe until a few kernel code paths are
- * updated. This allows us to get the kernel ready incrementally. Setting
- * unsafe_fsgsbase and TAINT_INSECURE flags will allow the series to be
- * bisected if necessary.
- *
- * Once all the pieces are in place, these will go away and be replaced with
- * a nofsgsbase chicken flag.
- */
-static bool unsafe_fsgsbase;
-
-static __init int setup_unsafe_fsgsbase(char *arg)
+static __init int x86_nofsgsbase_setup(char *arg)
{
- unsafe_fsgsbase = true;
- add_taint(TAINT_INSECURE, LOCKDEP_STILL_OK);
+ /* Require an exact match without trailing characters. */
+ if (strlen(arg))
+ return 0;
+
+ /* Do not emit a message if the feature is not present. */
+ if (!boot_cpu_has(X86_FEATURE_FSGSBASE))
+ return 1;
+
+ setup_clear_cpu_cap(X86_FEATURE_FSGSBASE);
+ pr_info("nofsgsbase: FSGSBASE disabled\n");
return 1;
}
-__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase);
+__setup("nofsgsbase", x86_nofsgsbase_setup);
/*
* Protection Keys are not available in 32-bit mode.
@@ -1372,12 +1369,8 @@ static void identify_cpu(struct cpuinfo_x86 *c)
setup_umip(c);
/* Enable FSGSBASE instructions if available. */
- if (cpu_has(c, X86_FEATURE_FSGSBASE)) {
- if (unsafe_fsgsbase)
- cr4_set_bits(X86_CR4_FSGSBASE);
- else
- clear_cpu_cap(c, X86_FEATURE_FSGSBASE);
- }
+ if (cpu_has(c, X86_FEATURE_FSGSBASE))
+ cr4_set_bits(X86_CR4_FSGSBASE);
/*
* The vendor-specific functions might have changed features.
--
2.19.1
next prev parent reply other threads:[~2019-01-16 22:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 22:48 [PATCH v4 00/13] x86: Enable FSGSBASE instructions Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 01/13] taint: Introduce a new taint flag (insecure) Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 02/13] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 03/13] kbuild: Raise the minimum required binutils version to 2.21 Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 04/13] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2019-01-17 5:09 ` Andi Kleen
2019-01-17 18:04 ` Bae, Chang Seok
2019-01-16 22:48 ` [PATCH v4 05/13] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 06/13] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 07/13] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 08/13] x86/fsgsbase/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 09/13] x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 10/13] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2019-01-16 22:48 ` Chang S. Bae [this message]
2019-01-16 22:48 ` [PATCH v4 12/13] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 13/13] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190116224849.8617-12-chang.seok.bae@intel.com \
--to=chang.seok.bae@intel.com \
--cc=ak@linux.intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=markus.t.metzger@intel.com \
--cc=mingo@kernel.org \
--cc=ravi.v.shankar@intel.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).