[PATCH] x86/ldt: Rename ldr_struct.size to .n_entries

[PATCH] x86/ldt: Rename ldr_struct.size to .n_entries

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

... because this is exactly what it is: the number of entries in the
LDT. Calling it "size" is simply confusing and it is actually begging
to be called "n_entries" or somesuch, especially if you see constructs
like:

	alloc_size = size * LDT_ENTRY_SIZE;

since LDT_ENTRY_SIZE is the size of a single entry.

There should be no functionality change resulting from this patch, as
the before/after output from tools/testing/selftests/x86/ldt_gdt.c
shows.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/events/core.c             |  2 +-
 arch/x86/include/asm/mmu_context.h |  4 ++--
 arch/x86/kernel/ldt.c              | 49 +++++++++++++++++++-------------------
 arch/x86/kernel/process_64.c       |  2 +-
 arch/x86/kernel/step.c             |  2 +-
 arch/x86/math-emu/fpu_system.h     |  2 +-
 6 files changed, 31 insertions(+), 30 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 400bea15f97e..c12b72f6972a 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2342,7 +2342,7 @@ static unsigned long get_segment_base(unsigned int segment)
 
 		/* IRQs are off, so this synchronizes with smp_store_release */
 		ldt = lockless_dereference(current->active_mm->context.ldt);
-		if (!ldt || idx > ldt->size)
+		if (!ldt || idx > ldt->n_entries)
 			return 0;
 
 		desc = &ldt->entries[idx];
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index f20d7ea47095..435b43f77ab3 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -47,7 +47,7 @@ struct ldt_struct {
 	 * allocations, but it's not worth trying to optimize.
 	 */
 	struct desc_struct *entries;
-	unsigned int size;
+	unsigned int n_entries;
 };
 
 /*
@@ -87,7 +87,7 @@ static inline void load_mm_ldt(struct mm_struct *mm)
 	 */
 
 	if (unlikely(ldt))
-		set_ldt(ldt->entries, ldt->size);
+		set_ldt(ldt->entries, ldt->n_entries);
 	else
 		clear_LDT();
 #else
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index de503e7a64ad..79aa4e56ee3b 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -31,16 +31,16 @@ static void flush_ldt(void *__mm)
 		return;
 
 	pc = &mm->context;
-	set_ldt(pc->ldt->entries, pc->ldt->size);
+	set_ldt(pc->ldt->entries, pc->ldt->n_entries);
 }
 
 /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
-static struct ldt_struct *alloc_ldt_struct(unsigned int size)
+static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
 {
 	struct ldt_struct *new_ldt;
 	unsigned int alloc_size;
 
-	if (size > LDT_ENTRIES)
+	if (num_entries > LDT_ENTRIES)
 		return NULL;
 
 	new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL);
@@ -48,7 +48,7 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int size)
 		return NULL;
 
 	BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct));
-	alloc_size = size * LDT_ENTRY_SIZE;
+	alloc_size = num_entries * LDT_ENTRY_SIZE;
 
 	/*
 	 * Xen is very picky: it requires a page-aligned LDT that has no
@@ -66,14 +66,14 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int size)
 		return NULL;
 	}
 
-	new_ldt->size = size;
+	new_ldt->n_entries = num_entries;
 	return new_ldt;
 }
 
 /* After calling this, the LDT is immutable. */
 static void finalize_ldt_struct(struct ldt_struct *ldt)
 {
-	paravirt_alloc_ldt(ldt->entries, ldt->size);
+	paravirt_alloc_ldt(ldt->entries, ldt->n_entries);
 }
 
 /* context.lock is held */
@@ -92,8 +92,8 @@ static void free_ldt_struct(struct ldt_struct *ldt)
 	if (likely(!ldt))
 		return;
 
-	paravirt_free_ldt(ldt->entries, ldt->size);
-	if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
+	paravirt_free_ldt(ldt->entries, ldt->n_entries);
+	if (ldt->n_entries * LDT_ENTRY_SIZE > PAGE_SIZE)
 		vfree_atomic(ldt->entries);
 	else
 		free_page((unsigned long)ldt->entries);
@@ -123,14 +123,14 @@ int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm)
 		goto out_unlock;
 	}
 
-	new_ldt = alloc_ldt_struct(old_mm->context.ldt->size);
+	new_ldt = alloc_ldt_struct(old_mm->context.ldt->n_entries);
 	if (!new_ldt) {
 		retval = -ENOMEM;
 		goto out_unlock;
 	}
 
 	memcpy(new_ldt->entries, old_mm->context.ldt->entries,
-	       new_ldt->size * LDT_ENTRY_SIZE);
+	       new_ldt->n_entries * LDT_ENTRY_SIZE);
 	finalize_ldt_struct(new_ldt);
 
 	mm->context.ldt = new_ldt;
@@ -153,9 +153,9 @@ void destroy_context_ldt(struct mm_struct *mm)
 
 static int read_ldt(void __user *ptr, unsigned long bytecount)
 {
-	int retval;
-	unsigned long size;
 	struct mm_struct *mm = current->mm;
+	unsigned long entries_size;
+	int retval;
 
 	mutex_lock(&mm->context.lock);
 
@@ -167,18 +167,18 @@ static int read_ldt(void __user *ptr, unsigned long bytecount)
 	if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
 		bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
 
-	size = mm->context.ldt->size * LDT_ENTRY_SIZE;
-	if (size > bytecount)
-		size = bytecount;
+	entries_size = mm->context.ldt->n_entries * LDT_ENTRY_SIZE;
+	if (entries_size > bytecount)
+		entries_size = bytecount;
 
-	if (copy_to_user(ptr, mm->context.ldt->entries, size)) {
+	if (copy_to_user(ptr, mm->context.ldt->entries, entries_size)) {
 		retval = -EFAULT;
 		goto out_unlock;
 	}
 
-	if (size != bytecount) {
+	if (entries_size != bytecount) {
 		/* Zero-fill the rest and pretend we read bytecount bytes. */
-		if (clear_user(ptr + size, bytecount - size)) {
+		if (clear_user(ptr + entries_size, bytecount - entries_size)) {
 			retval = -EFAULT;
 			goto out_unlock;
 		}
@@ -209,7 +209,7 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
 {
 	struct mm_struct *mm = current->mm;
 	struct ldt_struct *new_ldt, *old_ldt;
-	unsigned int oldsize, newsize;
+	unsigned int old_n_entries, new_n_entries;
 	struct user_desc ldt_info;
 	struct desc_struct ldt;
 	int error;
@@ -248,17 +248,18 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
 
 	mutex_lock(&mm->context.lock);
 
-	old_ldt = mm->context.ldt;
-	oldsize = old_ldt ? old_ldt->size : 0;
-	newsize = max(ldt_info.entry_number + 1, oldsize);
+	old_ldt       = mm->context.ldt;
+	old_n_entries = old_ldt ? old_ldt->n_entries : 0;
+	new_n_entries = max(ldt_info.entry_number + 1, old_n_entries);
 
 	error = -ENOMEM;
-	new_ldt = alloc_ldt_struct(newsize);
+	new_ldt = alloc_ldt_struct(new_n_entries);
 	if (!new_ldt)
 		goto out_unlock;
 
 	if (old_ldt)
-		memcpy(new_ldt->entries, old_ldt->entries, oldsize * LDT_ENTRY_SIZE);
+		memcpy(new_ldt->entries, old_ldt->entries, old_n_entries * LDT_ENTRY_SIZE);
+
 	new_ldt->entries[ldt_info.entry_number] = ldt;
 	finalize_ldt_struct(new_ldt);
 
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b6840bf3940b..95c76edc4587 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -142,7 +142,7 @@ void release_thread(struct task_struct *dead_task)
 			pr_warn("WARNING: dead process %s still has LDT? <%p/%d>\n",
 				dead_task->comm,
 				dead_task->mm->context.ldt->entries,
-				dead_task->mm->context.ldt->size);
+				dead_task->mm->context.ldt->n_entries);
 			BUG();
 		}
 #endif
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index f07f83b3611b..59b8b9470ed6 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -34,7 +34,7 @@ unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *re
 
 		mutex_lock(&child->mm->context.lock);
 		if (unlikely(!child->mm->context.ldt ||
-			     seg >= child->mm->context.ldt->size))
+			     seg >= child->mm->context.ldt->n_entries))
 			addr = -1L; /* bogus selector, access would fault */
 		else {
 			desc = &child->mm->context.ldt->entries[seg];
diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index 5e044d506b7a..8252636e8136 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -27,7 +27,7 @@ static inline struct desc_struct FPU_get_ldt_descriptor(unsigned seg)
 #ifdef CONFIG_MODIFY_LDT_SYSCALL
 	seg >>= 3;
 	mutex_lock(&current->mm->context.lock);
-	if (current->mm->context.ldt && seg < current->mm->context.ldt->size)
+	if (current->mm->context.ldt && seg < current->mm->context.ldt->n_entries)
 		ret = current->mm->context.ldt->entries[seg];
 	mutex_unlock(&current->mm->context.lock);
 #endif
-- 
2.13.0

Re: [PATCH] x86/ldt: Rename ldr_struct.size to .n_entries

[Andy Lutomirski]

On Tue, Jun 6, 2017 at 10:31 AM, Borislav Petkov <bp@alien8.de> wrote:
> From: Borislav Petkov <bp@suse.de>
>
> ... because this is exactly what it is: the number of entries in the
> LDT. Calling it "size" is simply confusing and it is actually begging
> to be called "n_entries" or somesuch, especially if you see constructs
> like:

In the subject: ldt_struct, perhaps?

Otherwise looks good.

Re: [PATCH] x86/ldt: Rename ldr_struct.size to .n_entries

[Borislav Petkov]

On Tue, Jun 06, 2017 at 03:20:22PM -0700, Andy Lutomirski wrote:
> In the subject: ldt_struct, perhaps?

Right. Committer, pls fix. :-)

> Otherwise looks good.

Thanks.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH] x86/ldt: Rename ldr_struct.size to .n_entries

[Ingo Molnar]

* Borislav Petkov <bp@alien8.de> wrote:

> On Tue, Jun 06, 2017 at 03:20:22PM -0700, Andy Lutomirski wrote:
> > In the subject: ldt_struct, perhaps?
> 
> Right. Committer, pls fix. :-)

Fixed. I also renamed 'n_entries' to 'nr_entries', which is the canonical form:

  triton:~/tip> git grep -w n_entries | wc -l
  191

  triton:~/tip> git grep -w nr_entries | wc -l
  743

If we do a rename, we should do it right, painted bright red! ;-)


Thanks,

	Ingo

[tip:x86/mm] x86/ldt: Rename ldt_struct::size to ::nr_entries

[tip-bot for Borislav Petkov]

Commit-ID:  bbf79d21bd4627a01ca8721c9373752819f8e4cc
Gitweb:     http://git.kernel.org/tip/bbf79d21bd4627a01ca8721c9373752819f8e4cc
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Tue, 6 Jun 2017 19:31:16 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 8 Jun 2017 09:28:21 +0200

x86/ldt: Rename ldt_struct::size to ::nr_entries

... because this is exactly what it is: the number of entries in the
LDT. Calling it "size" is simply confusing and it is actually begging
to be called "nr_entries" or somesuch, especially if you see constructs
like:

	alloc_size = size * LDT_ENTRY_SIZE;

since LDT_ENTRY_SIZE is the size of a single entry.

There should be no functionality change resulting from this patch, as
the before/after output from tools/testing/selftests/x86/ldt_gdt.c
shows.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170606173116.13977-1-bp@alien8.de
[ Renamed 'n_entries' to 'nr_entries' ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/core.c             |  2 +-
 arch/x86/include/asm/mmu_context.h |  4 ++--
 arch/x86/kernel/ldt.c              | 49 +++++++++++++++++++-------------------
 arch/x86/kernel/process_64.c       |  2 +-
 arch/x86/kernel/step.c             |  2 +-
 arch/x86/math-emu/fpu_system.h     |  2 +-
 6 files changed, 31 insertions(+), 30 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 77a3309..d4d5e1e 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2333,7 +2333,7 @@ static unsigned long get_segment_base(unsigned int segment)
 
 		/* IRQs are off, so this synchronizes with smp_store_release */
 		ldt = lockless_dereference(current->active_mm->context.ldt);
-		if (!ldt || idx > ldt->size)
+		if (!ldt || idx > ldt->nr_entries)
 			return 0;
 
 		desc = &ldt->entries[idx];
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index f20d7ea..5a93f62 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -47,7 +47,7 @@ struct ldt_struct {
 	 * allocations, but it's not worth trying to optimize.
 	 */
 	struct desc_struct *entries;
-	unsigned int size;
+	unsigned int nr_entries;
 };
 
 /*
@@ -87,7 +87,7 @@ static inline void load_mm_ldt(struct mm_struct *mm)
 	 */
 
 	if (unlikely(ldt))
-		set_ldt(ldt->entries, ldt->size);
+		set_ldt(ldt->entries, ldt->nr_entries);
 	else
 		clear_LDT();
 #else
diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index de503e7..a870910 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -31,16 +31,16 @@ static void flush_ldt(void *__mm)
 		return;
 
 	pc = &mm->context;
-	set_ldt(pc->ldt->entries, pc->ldt->size);
+	set_ldt(pc->ldt->entries, pc->ldt->nr_entries);
 }
 
 /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
-static struct ldt_struct *alloc_ldt_struct(unsigned int size)
+static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
 {
 	struct ldt_struct *new_ldt;
 	unsigned int alloc_size;
 
-	if (size > LDT_ENTRIES)
+	if (num_entries > LDT_ENTRIES)
 		return NULL;
 
 	new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL);
@@ -48,7 +48,7 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int size)
 		return NULL;
 
 	BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct));
-	alloc_size = size * LDT_ENTRY_SIZE;
+	alloc_size = num_entries * LDT_ENTRY_SIZE;
 
 	/*
 	 * Xen is very picky: it requires a page-aligned LDT that has no
@@ -66,14 +66,14 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int size)
 		return NULL;
 	}
 
-	new_ldt->size = size;
+	new_ldt->nr_entries = num_entries;
 	return new_ldt;
 }
 
 /* After calling this, the LDT is immutable. */
 static void finalize_ldt_struct(struct ldt_struct *ldt)
 {
-	paravirt_alloc_ldt(ldt->entries, ldt->size);
+	paravirt_alloc_ldt(ldt->entries, ldt->nr_entries);
 }
 
 /* context.lock is held */
@@ -92,8 +92,8 @@ static void free_ldt_struct(struct ldt_struct *ldt)
 	if (likely(!ldt))
 		return;
 
-	paravirt_free_ldt(ldt->entries, ldt->size);
-	if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
+	paravirt_free_ldt(ldt->entries, ldt->nr_entries);
+	if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE)
 		vfree_atomic(ldt->entries);
 	else
 		free_page((unsigned long)ldt->entries);
@@ -123,14 +123,14 @@ int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm)
 		goto out_unlock;
 	}
 
-	new_ldt = alloc_ldt_struct(old_mm->context.ldt->size);
+	new_ldt = alloc_ldt_struct(old_mm->context.ldt->nr_entries);
 	if (!new_ldt) {
 		retval = -ENOMEM;
 		goto out_unlock;
 	}
 
 	memcpy(new_ldt->entries, old_mm->context.ldt->entries,
-	       new_ldt->size * LDT_ENTRY_SIZE);
+	       new_ldt->nr_entries * LDT_ENTRY_SIZE);
 	finalize_ldt_struct(new_ldt);
 
 	mm->context.ldt = new_ldt;
@@ -153,9 +153,9 @@ void destroy_context_ldt(struct mm_struct *mm)
 
 static int read_ldt(void __user *ptr, unsigned long bytecount)
 {
-	int retval;
-	unsigned long size;
 	struct mm_struct *mm = current->mm;
+	unsigned long entries_size;
+	int retval;
 
 	mutex_lock(&mm->context.lock);
 
@@ -167,18 +167,18 @@ static int read_ldt(void __user *ptr, unsigned long bytecount)
 	if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
 		bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
 
-	size = mm->context.ldt->size * LDT_ENTRY_SIZE;
-	if (size > bytecount)
-		size = bytecount;
+	entries_size = mm->context.ldt->nr_entries * LDT_ENTRY_SIZE;
+	if (entries_size > bytecount)
+		entries_size = bytecount;
 
-	if (copy_to_user(ptr, mm->context.ldt->entries, size)) {
+	if (copy_to_user(ptr, mm->context.ldt->entries, entries_size)) {
 		retval = -EFAULT;
 		goto out_unlock;
 	}
 
-	if (size != bytecount) {
+	if (entries_size != bytecount) {
 		/* Zero-fill the rest and pretend we read bytecount bytes. */
-		if (clear_user(ptr + size, bytecount - size)) {
+		if (clear_user(ptr + entries_size, bytecount - entries_size)) {
 			retval = -EFAULT;
 			goto out_unlock;
 		}
@@ -209,7 +209,7 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
 {
 	struct mm_struct *mm = current->mm;
 	struct ldt_struct *new_ldt, *old_ldt;
-	unsigned int oldsize, newsize;
+	unsigned int old_nr_entries, new_nr_entries;
 	struct user_desc ldt_info;
 	struct desc_struct ldt;
 	int error;
@@ -248,17 +248,18 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
 
 	mutex_lock(&mm->context.lock);
 
-	old_ldt = mm->context.ldt;
-	oldsize = old_ldt ? old_ldt->size : 0;
-	newsize = max(ldt_info.entry_number + 1, oldsize);
+	old_ldt       = mm->context.ldt;
+	old_nr_entries = old_ldt ? old_ldt->nr_entries : 0;
+	new_nr_entries = max(ldt_info.entry_number + 1, old_nr_entries);
 
 	error = -ENOMEM;
-	new_ldt = alloc_ldt_struct(newsize);
+	new_ldt = alloc_ldt_struct(new_nr_entries);
 	if (!new_ldt)
 		goto out_unlock;
 
 	if (old_ldt)
-		memcpy(new_ldt->entries, old_ldt->entries, oldsize * LDT_ENTRY_SIZE);
+		memcpy(new_ldt->entries, old_ldt->entries, old_nr_entries * LDT_ENTRY_SIZE);
+
 	new_ldt->entries[ldt_info.entry_number] = ldt;
 	finalize_ldt_struct(new_ldt);
 
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index b6840bf..9c39ab8 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -142,7 +142,7 @@ void release_thread(struct task_struct *dead_task)
 			pr_warn("WARNING: dead process %s still has LDT? <%p/%d>\n",
 				dead_task->comm,
 				dead_task->mm->context.ldt->entries,
-				dead_task->mm->context.ldt->size);
+				dead_task->mm->context.ldt->nr_entries);
 			BUG();
 		}
 #endif
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index f07f83b..5f25cfb 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -34,7 +34,7 @@ unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *re
 
 		mutex_lock(&child->mm->context.lock);
 		if (unlikely(!child->mm->context.ldt ||
-			     seg >= child->mm->context.ldt->size))
+			     seg >= child->mm->context.ldt->nr_entries))
 			addr = -1L; /* bogus selector, access would fault */
 		else {
 			desc = &child->mm->context.ldt->entries[seg];
diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index 5e044d5..a179254 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -27,7 +27,7 @@ static inline struct desc_struct FPU_get_ldt_descriptor(unsigned seg)
 #ifdef CONFIG_MODIFY_LDT_SYSCALL
 	seg >>= 3;
 	mutex_lock(&current->mm->context.lock);
-	if (current->mm->context.ldt && seg < current->mm->context.ldt->size)
+	if (current->mm->context.ldt && seg < current->mm->context.ldt->nr_entries)
 		ret = current->mm->context.ldt->entries[seg];
 	mutex_unlock(&current->mm->context.lock);
 #endif