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x86: x86 TLS desc_struct cleanup
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This cleans up the TLS code to use struct desc_struct and to separate the
encoding and installation magic from the interface wrappers.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Roland McGrath authored and Ingo Molnar committed Jan 30, 2008
1 parent 1eeaed7 commit 1bd5718
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Showing 2 changed files with 54 additions and 46 deletions.
89 changes: 45 additions & 44 deletions arch/x86/kernel/tls.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,17 +24,37 @@ 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:
*/
int do_set_thread_area(struct task_struct *p, int idx,
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;
Expand All @@ -57,23 +77,8 @@ int do_set_thread_area(struct task_struct *p, int idx,
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;

desc = (u32 *) &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
set_tls_desc(p, idx, &info);

/*
* 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);

if (t == &current->thread)
load_TLS(t, cpu);

put_cpu();
return 0;
}

Expand All @@ -87,42 +92,38 @@ asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
* 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;

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;
Expand Down
11 changes: 9 additions & 2 deletions include/asm-x86/desc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -275,10 +276,16 @@ static inline void load_LDT(mm_context_t *pc)
preempt_enable();
}

static inline unsigned long get_desc_base(struct desc_struct *desc)
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)
{
Expand Down

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