[PATCH] i386: remove default_ldt, and simplify ldt-setting.

This patch removes the default_ldt[] array, as it has been unused since
iBCS stopped being supported.  This means it is now possible to actually
set an empty LDT segment.

In order to deal with this, the set_ldt_desc/load_LDT pair has been
replaced with a single set_ldt() operation which is responsible for both
setting up the LDT descriptor in the GDT, and reloading the LDT register.
If there are no LDT entries, the LDT register is loaded with a NULL
descriptor.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Acked-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

diff --git a/arch/i386/kernel/ldt.c b/arch/i386/kernel/ldt.c
index 445211eb2d57cdfcab06bb2a0b1f3b2b6b6ad5da..b410e5fb034f285346ef41c4cc6929db3081790b 100644 (file)
--- a/arch/i386/kernel/ldt.c
+++ b/arch/i386/kernel/ldt.c
@@ -160,16 +160,14 @@ static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 {
        int err;
        unsigned long size;
-       void *address;
 
        err = 0;
-       address = &default_ldt[0];
        size = 5*sizeof(struct desc_struct);
        if (size > bytecount)
                size = bytecount;
 
        err = size;
-       if (copy_to_user(ptr, address, size))
+       if (clear_user(ptr, size))
                err = -EFAULT;
 
        return err;

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 48ebfab661b747eb6ff37ca6adbac4c7085ae474..56655ea8d98f62aed4744772b9b2cce8dde1f6b8 100644 (file)
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -61,9 +61,6 @@ int panic_on_unrecovered_nmi;
 
 asmlinkage int system_call(void);
 
-struct desc_struct default_ldt[] = { { 0, 0 }, { 0, 0 }, { 0, 0 },
-               { 0, 0 }, { 0, 0 } };
-
 /* Do we ignore FPU interrupts ? */
 char ignore_fpu_irq = 0;
 

diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 5874ef119ffdc0cf42886585c2c8aed229cfb91e..a0398f780ca11782f699e955373c8c689cfbad3e 100644 (file)
--- a/include/asm-i386/desc.h
+++ b/include/asm-i386/desc.h
@@ -33,11 +33,6 @@ static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
        return (struct desc_struct *)per_cpu(cpu_gdt_descr, cpu).address;
 }
 
-/*
- * This is the ldt that every process will get unless we need
- * something other than this.
- */
-extern struct desc_struct default_ldt[];
 extern struct desc_struct idt_table[];
 extern void set_intr_gate(unsigned int irq, void * addr);
 
@@ -65,7 +60,6 @@ static inline void pack_gate(__u32 *a, __u32 *b,
 #define DESCTYPE_S     0x10    /* !system */
 
 #define load_TR_desc() __asm__ __volatile__("ltr %w0"::"q" (GDT_ENTRY_TSS*8))
-#define load_LDT_desc() __asm__ __volatile__("lldt %w0"::"q" (GDT_ENTRY_LDT*8))
 
 #define load_gdt(dtr) __asm__ __volatile("lgdt %0"::"m" (*dtr))
 #define load_idt(dtr) __asm__ __volatile("lidt %0"::"m" (*dtr))
@@ -115,13 +109,20 @@ static inline void __set_tss_desc(unsigned int cpu, unsigned int entry, const vo
        write_gdt_entry(get_cpu_gdt_table(cpu), entry, a, b);
 }
 
-static inline void set_ldt_desc(unsigned int cpu, void *addr, unsigned int entries)
+static inline void set_ldt(void *addr, unsigned int entries)
 {
-       __u32 a, b;
-       pack_descriptor(&a, &b, (unsigned long)addr,
-                       entries * sizeof(struct desc_struct) - 1,
-                       DESCTYPE_LDT, 0);
-       write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_LDT, a, b);
+       if (likely(entries == 0))
+               __asm__ __volatile__("lldt %w0"::"q" (0));
+       else {
+               unsigned cpu = smp_processor_id();
+               __u32 a, b;
+
+               pack_descriptor(&a, &b, (unsigned long)addr,
+                               entries * sizeof(struct desc_struct) - 1,
+                               DESCTYPE_LDT, 0);
+               write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_LDT, a, b);
+               __asm__ __volatile__("lldt %w0"::"q" (GDT_ENTRY_LDT*8));
+       }
 }
 
 #define set_tss_desc(cpu,addr) __set_tss_desc(cpu, GDT_ENTRY_TSS, addr)
@@ -153,35 +154,22 @@ static inline void set_ldt_desc(unsigned int cpu, void *addr, unsigned int entri
 
 static inline void clear_LDT(void)
 {
-       int cpu = get_cpu();
-
-       set_ldt_desc(cpu, &default_ldt[0], 5);
-       load_LDT_desc();
-       put_cpu();
+       set_ldt(NULL, 0);
 }
 
 /*
  * load one particular LDT into the current CPU
  */
-static inline void load_LDT_nolock(mm_context_t *pc, int cpu)
+static inline void load_LDT_nolock(mm_context_t *pc)
 {
-       void *segments = pc->ldt;
-       int count = pc->size;
-
-       if (likely(!count)) {
-               segments = &default_ldt[0];
-               count = 5;
-       }
-               
-       set_ldt_desc(cpu, segments, count);
-       load_LDT_desc();
+       set_ldt(pc->ldt, pc->size);
 }
 
 static inline void load_LDT(mm_context_t *pc)
 {
-       int cpu = get_cpu();
-       load_LDT_nolock(pc, cpu);
-       put_cpu();
+       preempt_disable();
+       load_LDT_nolock(pc);
+       preempt_enable();
 }
 
 static inline unsigned long get_desc_base(unsigned long *desc)

diff --git a/include/asm-i386/mmu_context.h b/include/asm-i386/mmu_context.h
index 62b7bf1840942013a0a258a039a03e90c8458a66..1b1495372c4d59ddbf9294c06d73b452467679c0 100644 (file)
--- a/include/asm-i386/mmu_context.h
+++ b/include/asm-i386/mmu_context.h
@@ -44,7 +44,7 @@ static inline void switch_mm(struct mm_struct *prev,
                 * load the LDT, if the LDT is different:
                 */
                if (unlikely(prev->context.ldt != next->context.ldt))
-                       load_LDT_nolock(&next->context, cpu);
+                       load_LDT_nolock(&next->context);
        }
 #ifdef CONFIG_SMP
        else {
@@ -56,7 +56,7 @@ static inline void switch_mm(struct mm_struct *prev,
                         * tlb flush IPI delivery. We must reload %cr3.
                         */
                        load_cr3(next->pgd);
-                       load_LDT_nolock(&next->context, cpu);
+                       load_LDT_nolock(&next->context);
                }
        }
 #endif