linux-kernel - [PATCH 27/31] x86: separate out LDT init from context init

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Message-Id: <20160129181721.760F9F10@viggo.jf.intel.com>
Date:	Fri, 29 Jan 2016 10:17:21 -0800
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, x86@...nel.org, torvalds@...ux-foundation.org,
	Dave Hansen <dave@...1.net>, dave.hansen@...ux.intel.com
Subject: [PATCH 27/31] x86: separate out LDT init from context init


From: Dave Hansen <dave.hansen@...ux.intel.com>

The arch-specific mm_context_t is a great place to put
protection-key allocation state.

But, we need to initialize the allocation state because pkey 0 is
always "allocated".  All of the runtime initialization of
mm_context_t is done in *_ldt() manipulation functions.  This
renames the existing LDT functions like this:

	init_new_context() -> init_new_context_ldt()
	destroy_context() -> destroy_context_ldt()

and makes init_new_context() and destroy_context() available for
generic use.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
---

 b/arch/x86/include/asm/mmu_context.h |   21 ++++++++++++++++-----
 b/arch/x86/kernel/ldt.c              |    4 ++--
 2 files changed, 18 insertions(+), 7 deletions(-)

diff -puN arch/x86/include/asm/mmu_context.h~pkeys-72-init-ldt-extricate arch/x86/include/asm/mmu_context.h
--- a/arch/x86/include/asm/mmu_context.h~pkeys-72-init-ldt-extricate	2016-01-28 15:52:28.756788858 -0800
+++ b/arch/x86/include/asm/mmu_context.h	2016-01-28 15:52:28.761789087 -0800
@@ -52,15 +52,15 @@ struct ldt_struct {
 /*
  * Used for LDT copy/destruction.
  */
-int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
-void destroy_context(struct mm_struct *mm);
+int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm);
+void destroy_context_ldt(struct mm_struct *mm);
 #else	/* CONFIG_MODIFY_LDT_SYSCALL */
-static inline int init_new_context(struct task_struct *tsk,
-				   struct mm_struct *mm)
+static inline int init_new_context_ldt(struct task_struct *tsk,
+				       struct mm_struct *mm)
 {
 	return 0;
 }
-static inline void destroy_context(struct mm_struct *mm) {}
+static inline void destroy_context_ldt(struct mm_struct *mm) {}
 #endif
 
 static inline void load_mm_ldt(struct mm_struct *mm)
@@ -104,6 +104,17 @@ static inline void enter_lazy_tlb(struct
 #endif
 }
 
+static inline int init_new_context(struct task_struct *tsk,
+				   struct mm_struct *mm)
+{
+	init_new_context_ldt(tsk, mm);
+	return 0;
+}
+static inline void destroy_context(struct mm_struct *mm)
+{
+	destroy_context_ldt(mm);
+}
+
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 			     struct task_struct *tsk)
 {
diff -puN arch/x86/kernel/ldt.c~pkeys-72-init-ldt-extricate arch/x86/kernel/ldt.c
--- a/arch/x86/kernel/ldt.c~pkeys-72-init-ldt-extricate	2016-01-28 15:52:28.758788949 -0800
+++ b/arch/x86/kernel/ldt.c	2016-01-28 15:52:28.761789087 -0800
@@ -103,7 +103,7 @@ static void free_ldt_struct(struct ldt_s
  * we do not have to muck with descriptors here, that is
  * done in switch_mm() as needed.
  */
-int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm)
 {
 	struct ldt_struct *new_ldt;
 	struct mm_struct *old_mm;
@@ -144,7 +144,7 @@ out_unlock:
  *
  * 64bit: Don't touch the LDT register - we're already in the next thread.
  */
-void destroy_context(struct mm_struct *mm)
+void destroy_context_ldt(struct mm_struct *mm)
 {
 	free_ldt_struct(mm->context.ldt);
 	mm->context.ldt = NULL;
_