[PATCH] i386: cleanup GDT Access

Now we have an explicit per-cpu GDT variable, we don't need to keep the
descriptors around to use them to find the GDT: expose cpu_gdt directly.

We could go further and make load_gdt() pack the descriptor for us, or even
assume it means "load the current cpu's GDT" which is what it always does.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

6 files changed, 19 insertions, 27 deletions

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 2a26956fce42..5faf675aab4b 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -22,9 +22,6 @@
 
 #include "cpu.h"
 
-DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
-EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
-
 DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]) = {
         [GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 },
         [GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 },
@@ -52,6 +49,7 @@ DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]) = {
         [GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00c09200 },
         [GDT_ENTRY_PDA] = { 0x00000000, 0x00c09200 }, /* set in setup_pda */
 };
+EXPORT_PER_CPU_SYMBOL_GPL(cpu_gdt);
 
 DEFINE_PER_CPU(struct i386_pda, _cpu_pda);
 EXPORT_PER_CPU_SYMBOL(_cpu_pda);
diff --git a/arch/i386/kernel/efi.c b/arch/i386/kernel/efi.c
index 8f9c624ace6f..dd9e7faafa7c 100644
--- a/arch/i386/kernel/efi.c
+++ b/arch/i386/kernel/efi.c
@@ -69,13 +69,11 @@ static void efi_call_phys_prelog(void) __acquires(efi_rt_lock)
 {
         unsigned long cr4;
         unsigned long temp;
-        struct Xgt_desc_struct *cpu_gdt_descr;
+        struct Xgt_desc_struct gdt_descr;
 
         spin_lock(&efi_rt_lock);
         local_irq_save(efi_rt_eflags);
 
-        cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
-
         /*
          * If I don't have PSE, I should just duplicate two entries in page
          * directory. If I have PSE, I just need to duplicate one entry in
@@ -105,17 +103,19 @@ static void efi_call_phys_prelog(void) __acquires(efi_rt_lock)
          */
         local_flush_tlb();
 
-        cpu_gdt_descr->address = __pa(cpu_gdt_descr->address);
-        load_gdt(cpu_gdt_descr);
+        gdt_descr.address = __pa(get_cpu_gdt_table(0));
+        gdt_descr.size = GDT_SIZE - 1;
+        load_gdt(&gdt_descr);
 }
 
 static void efi_call_phys_epilog(void) __releases(efi_rt_lock)
 {
         unsigned long cr4;
-        struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
+        struct Xgt_desc_struct gdt_descr;
 
-        cpu_gdt_descr->address = (unsigned long)__va(cpu_gdt_descr->address);
-        load_gdt(cpu_gdt_descr);
+        gdt_descr.address = (unsigned long)get_cpu_gdt_table(0);
+        gdt_descr.size = GDT_SIZE - 1;
+        load_gdt(&gdt_descr);
 
         cr4 = read_cr4();
 
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 922cc38dc405..c61c6b67e856 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -561,8 +561,7 @@ END(syscall_badsys)
 #define FIXUP_ESPFIX_STACK \
         /* since we are on a wrong stack, we cant make it a C code :( */ \
         movl %fs:PDA_cpu, %ebx; \
-        PER_CPU(cpu_gdt_descr, %ebx); \
-        movl GDS_address(%ebx), %ebx; \
+        PER_CPU(cpu_gdt, %ebx); \
         GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah); \
         addl %esp, %eax; \
         pushl $__KERNEL_DS; \
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 954245f6d307..b0ad04d9ef21 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -786,13 +786,9 @@ static inline struct task_struct * alloc_idle_task(int cpu)
    secondary which will soon come up. */
 static __cpuinit void init_gdt(int cpu, struct task_struct *idle)
 {
-        struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
-        struct desc_struct *gdt = per_cpu(cpu_gdt, cpu);
+        struct desc_struct *gdt = get_cpu_gdt_table(cpu);
         struct i386_pda *pda = &per_cpu(_cpu_pda, cpu);
 
-        cpu_gdt_descr->address = (unsigned long)gdt;
-        cpu_gdt_descr->size = GDT_SIZE - 1;
-
         pack_descriptor((u32 *)&gdt[GDT_ENTRY_PDA].a,
                         (u32 *)&gdt[GDT_ENTRY_PDA].b,
                         (unsigned long)pda, sizeof(*pda) - 1,
@@ -1187,7 +1183,11 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
  * it's on the real one. */
 static inline void switch_to_new_gdt(void)
 {
-        load_gdt(&per_cpu(cpu_gdt_descr, smp_processor_id()));
+        struct Xgt_desc_struct gdt_descr;
+
+        gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());
+        gdt_descr.size = GDT_SIZE - 1;
+        load_gdt(&gdt_descr);
         asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_PDA) : "memory");
 }
 
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 58dfecc8e36c..8722444cacaa 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -1030,9 +1030,7 @@ fastcall void do_spurious_interrupt_bug(struct pt_regs * regs,
 fastcall unsigned long patch_espfix_desc(unsigned long uesp,
                                           unsigned long kesp)
 {
-        int cpu = smp_processor_id();
-        struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
-        struct desc_struct *gdt = (struct desc_struct *)cpu_gdt_descr->address;
+        struct desc_struct *gdt = __get_cpu_var(cpu_gdt);
         unsigned long base = (kesp - uesp) & -THREAD_SIZE;
         unsigned long new_kesp = kesp - base;
         unsigned long lim_pages = (new_kesp | (THREAD_SIZE - 1)) >> PAGE_SHIFT;
diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 13f701ea9a8f..4a974064e928 100644
--- a/include/asm-i386/desc.h
+++ b/include/asm-i386/desc.h
@@ -18,16 +18,13 @@ struct Xgt_desc_struct {
         unsigned short pad;
 } __attribute__ ((packed));
 
-extern struct Xgt_desc_struct idt_descr;
-DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
 DECLARE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]);
-extern struct Xgt_desc_struct early_gdt_descr;
-
 static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
 {
-        return (struct desc_struct *)per_cpu(cpu_gdt_descr, cpu).address;
+        return per_cpu(cpu_gdt, cpu);
 }
 
+extern struct Xgt_desc_struct idt_descr;
 extern struct desc_struct idt_table[];
 extern void set_intr_gate(unsigned int irq, void * addr);