LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86/ldt: Rename ldr_struct.size to .n_entries
Date: Tue,  6 Jun 2017 19:31:16 +0200
Message-ID: <20170606173116.13977-1-bp@alien8.de> (raw)

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

             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-06 17:31 Borislav Petkov [this message]
2017-06-06 22:20 ` Andy Lutomirski
2017-06-07 10:24   ` Borislav Petkov
2017-06-08  7:27     ` Ingo Molnar
2017-06-08  9:19 ` [tip:x86/mm] x86/ldt: Rename ldt_struct::size to ::nr_entries tip-bot for Borislav Petkov

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=20170606173116.13977-1-bp@alien8.de \
    --to=bp@alien8.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=x86@kernel.org \
    /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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git