[PATCH x86/mm] x86: TLS desc_struct cleanup

Roland McGrath
2007-12-18T06:00:26Z

This cleans up the x86 TLS code to use desc_struct in place of hand-coded
bit-twiddling, and cleans up a few of the inlines for the type too.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/x86/kernel/tls.c | 89 ++++++++++++++++++++--------------------
include/asm-x86/desc.h | 16 ++++++-
include/asm-x86/processor_32.h | 18 +++-----
include/asm-x86/processor_64.h | 48 +++++++++------------
4 files changed, 86 insertions(+), 85 deletions(-)

diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 98f428b..f11c92a 100644
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -24,6 +24,29 @@ static int get_free_idx(void)
return -ESRCH;
}

+static void set_tls_desc(struct task_struct *p, int idx,
+ const struct user_desc *info)
+{
+ struct thread_struct *t = &p->thread;
+ struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
+ int cpu;
+
+ /*
+ * We must not get preempted while modifying the TLS.
+ */
+ cpu = get_cpu();
+
+ if (LDT_empty(info))
+ desc->a = desc->b = 0;
+ else
+ fill_ldt(desc, info);
+
+ if (t == &current->thread)
+ load_TLS(t, cpu);
+
+ put_cpu();
+}
+
/*
* Set a given TLS descriptor:
*/
@@ -31,10 +54,7 @@ int do_set_thread_area(struct task_struc
struct user_desc __user *u_info,
int can_allocate)
{
- struct thread_struct *t = &p->thread;
struct user_desc info;
- u32 *desc;
- int cpu;

if (copy_from_user(&info, u_info, sizeof(info)))
return -EFAULT;
@@ -57,23 +77,8 @@ int do_set_thread_area(struct task_struc
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;

- desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
-
- /*
- * We must not get preempted while modifying the TLS.
- */
- cpu = get_cpu();
-
- if (LDT_empty(&info)) {
- desc[0] = 0;
- desc[1] = 0;
- } else
- fill_ldt((struct desc_struct *)desc, &info);
+ set_tls_desc(p, idx, &info);

- if (t == &current->thread)
- load_TLS(t, cpu);
-
- put_cpu();
return 0;
}

@@ -87,21 +92,29 @@ asmlinkage int sys_set_thread_area(struc
* Get the current Thread-Local Storage area:
*/

-#define GET_LIMIT(desc) (((desc)[0] & 0x0ffff) | ((desc)[1] & 0xf0000))
-#define GET_32BIT(desc) (((desc)[1] >> 22) & 1)
-#define GET_CONTENTS(desc) (((desc)[1] >> 10) & 3)
-#define GET_WRITABLE(desc) (((desc)[1] >> 9) & 1)
-#define GET_LIMIT_PAGES(desc) (((desc)[1] >> 23) & 1)
-#define GET_PRESENT(desc) (((desc)[1] >> 15) & 1)
-#define GET_USEABLE(desc) (((desc)[1] >> 20) & 1)
-#define GET_LONGMODE(desc) (((desc)[1] >> 21) & 1)
+static void fill_user_desc(struct user_desc *info, int idx,
+ const struct desc_struct *desc)
+
+{
+ memset(info, 0, sizeof(*info));
+ info->entry_number = idx;
+ info->base_addr = get_desc_base(desc);
+ info->limit = get_desc_limit(desc);
+ info->seg_32bit = desc->d;
+ info->contents = desc->type >> 2;
+ info->read_exec_only = !(desc->type & 2);
+ info->limit_in_pages = desc->g;
+ info->seg_not_present = !desc->p;
+ info->useable = desc->avl;
+#ifdef CONFIG_X86_64
+ info->lm = desc->l;
+#endif
+}

int do_get_thread_area(struct task_struct *p, int idx,
struct user_desc __user *u_info)
{
- struct thread_struct *t = &p->thread;
struct user_desc info;
- u32 *desc;

if (idx == -1 && get_user(idx, &u_info->entry_number))
return -EFAULT;
@@ -108,21 +122,8 @@ int do_get_thread_area(struct task_struc
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;

- desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
-
- memset(&info, 0, sizeof(struct user_desc));
- info.entry_number = idx;
- info.base_addr = get_desc_base((struct desc_struct *)desc);
- info.limit = GET_LIMIT(desc);
- info.seg_32bit = GET_32BIT(desc);
- info.contents = GET_CONTENTS(desc);
- info.read_exec_only = !GET_WRITABLE(desc);
- info.limit_in_pages = GET_LIMIT_PAGES(desc);
- info.seg_not_present = !GET_PRESENT(desc);
- info.useable = GET_USEABLE(desc);
-#ifdef CONFIG_X86_64
- info.lm = GET_LONGMODE(desc);
-#endif
+ fill_user_desc(&info, idx,
+ &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);

if (copy_to_user(u_info, &info, sizeof(info)))
return -EFAULT;
diff --git a/include/asm-x86/desc.h b/include/asm-x86/desc.h
index 161a6d6..0000000 100644
--- a/include/asm-x86/desc.h
+++ b/include/asm-x86/desc.h
@@ -7,7 +7,8 @@
#include <asm/mmu.h>
#include <linux/smp.h>

-static inline void fill_ldt(struct desc_struct *desc, struct user_desc *info)
+static inline void fill_ldt(struct desc_struct *desc,
+ const struct user_desc *info)
{
desc->limit0 = info->limit & 0x0ffff;
desc->base0 = info->base_addr & 0x0000ffff;
@@ -269,10 +270,21 @@ static inline void load_LDT(mm_context_t
preempt_enable();
}

-static inline unsigned long get_desc_base(struct desc_struct *desc)
+static inline int desc_empty(const struct desc_struct *desc)
+{
+ return !(desc->a | desc->b);
+}
+
+static inline unsigned long get_desc_base(const struct desc_struct *desc)
{
return desc->base0 | ((desc->base1) << 16) | ((desc->base2) << 24);
}
+
+static inline unsigned long get_desc_limit(const struct desc_struct *desc)
+{
+ return desc->limit0 | (desc->limit << 16);
+}
+
static inline void _set_gate(int gate, unsigned type, void *addr,
unsigned dpl, unsigned ist, unsigned seg)
{
diff --git a/include/asm-x86/processor_32.h b/include/asm-x86/processor_32.h
index a5560a3..0000000 100644
--- a/include/asm-x86/processor_32.h
+++ b/include/asm-x86/processor_32.h
@@ -25,12 +25,6 @@
/* flag for disabling the tsc */
extern int tsc_disable;

-static inline int desc_empty(const void *ptr)
-{
- const u32 *desc = ptr;
- return !(desc[0] | desc[1]);
-}
-
/*
* Default implementation of macro that returns current
* instruction pointer ("program counter").
diff --git a/include/asm-x86/processor_64.h b/include/asm-x86/processor_64.h
index 51f1970..0000000 100644
--- a/include/asm-x86/processor_64.h
+++ b/include/asm-x86/processor_64.h
@@ -31,12 +31,6 @@
#define VIP_MASK 0x00100000 /* virtual interrupt pending */
#define ID_MASK 0x00200000

-static inline int desc_empty(const void *ptr)
-{
- const u32 *desc = ptr;
- return !(desc[0] | desc[1]);
-}
-
/*
* Default implementation of macro that returns current
* instruction pointer ("program counter").