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From: "H. Peter Anvin, Intel" <h.peter.anvin@intel.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>,
	"Chang S . Bae" <chang.seok.bae@intel.com>,
	"Markus T . Metzger" <markus.t.metzger@intel.com>
Subject: [PATCH v3 5/7] x86/segment: add #define for the last user-visible GDT slot
Date: Thu, 21 Jun 2018 14:17:52 -0700	[thread overview]
Message-ID: <20180621211754.12757-6-h.peter.anvin@intel.com> (raw)
In-Reply-To: <20180621211754.12757-1-h.peter.anvin@intel.com>

From: "H. Peter Anvin" <hpa@linux.intel.com>

We don't want to advertise to user space how many slots the kernel
GDT has, but user space can trivially find out what the last
user-accessible GDT slot is.  Add a #define for that so we can use
that in sizing a regset.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Markus T. Metzger <markus.t.metzger@intel.com>
---
 arch/x86/include/asm/segment.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index e293c122d0d5..5eb809eec048 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -115,6 +115,11 @@
  */
 #define GDT_ENTRIES			32
 
+/*
+ * Last user-visible GDT slot
+ */
+#define GDT_LAST_USER			GDT_ENTRY_DEFAULT_USER_DS
+
 /*
  * Segment selector values corresponding to the above entries:
  */
@@ -194,6 +199,11 @@
  */
 #define GDT_ENTRIES			16
 
+/*
+ * Last user-visible GDT slot
+ */
+#define GDT_LAST_USER			GDT_ENTRY_PER_CPU
+
 /*
  * Segment selector values corresponding to the above entries:
  *
-- 
2.14.4


  parent reply	other threads:[~2018-06-21 21:18 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-21 21:17 [PATCH v3 0/7] x86/ptrace: regset access to the GDT and LDT H. Peter Anvin, Intel
2018-06-21 21:17 ` [PATCH v3 1/7] x86/ldt: refresh %fs and %gs in refresh_ldt_segments() H. Peter Anvin, Intel
2018-06-22 14:24   ` Andy Lutomirski
2018-06-22 18:29     ` H. Peter Anvin
2018-06-22 18:47       ` Andy Lutomirski
2018-06-27 18:19         ` Andy Lutomirski
2018-06-27 18:22           ` hpa
2018-06-27 18:33             ` hpa
2018-06-28 20:33             ` Andy Lutomirski
2018-06-28 20:39               ` hpa
2018-06-21 21:17 ` [PATCH v3 2/7] x86/ldt: use a common value for read_default_ldt() H. Peter Anvin, Intel
2018-06-21 21:17 ` [PATCH v3 3/7] x86: move fill_user_desc() from tls.c to desc.h and add validity check H. Peter Anvin, Intel
2018-06-21 21:17 ` [PATCH v3 4/7] x86/tls: create an explicit config symbol for the TLS area in the GDT H. Peter Anvin, Intel
2018-06-21 21:17 ` H. Peter Anvin, Intel [this message]
2018-06-21 21:17 ` [PATCH v3 6/7] x86/tls,ptrace: provide regset access to " H. Peter Anvin, Intel
2018-06-22 14:43   ` Andy Lutomirski
2018-06-21 21:17 ` [PATCH v3 7/7] x86/ldt,ptrace: provide regset access to the LDT H. Peter Anvin, Intel
2018-06-22 14:49   ` Andy Lutomirski
2018-06-22 15:05     ` hpa
2018-06-22 15:30       ` Andy Lutomirski
2018-06-22  1:58 ` [PATCH v3 0/7] x86/ptrace: regset access to the GDT and LDT Ingo Molnar
2018-06-22  2:25   ` hpa

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