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Subject[patch] x86_64: align and pad x86_64 GDT on page boundary
This patch is on the same lines as Zachary Amsden's i386 GDT page alignemnt 
patch in -mm, but for x86_64.

Thanks,
Kiran


Patch to align and pad x86_64 GDT on page boundries.

Signed-off-by: Nippun Goel <nippung@calsoftinc.com>
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>


Index: linux-2.6.15-rc3/arch/x86_64/kernel/head.S
===================================================================
--- linux-2.6.15-rc3.orig/arch/x86_64/kernel/head.S 2005-12-01 15:49:27.000000000 -0800
+++ linux-2.6.15-rc3/arch/x86_64/kernel/head.S 2005-12-01 16:19:29.000000000 -0800
@@ -379,7 +379,7 @@
* Also sysret mandates a special GDT layout
*/

-.align L1_CACHE_BYTES
+.align PAGE_SIZE

/* The TLS descriptors are currently at a different place compared to i386.
Hopefully nobody expects them at a fixed place (Wine?) */
@@ -401,10 +401,11 @@
gdt_end:
/* asm/segment.h:GDT_ENTRIES must match this */
/* This should be a multiple of the cache line size */
- /* GDTs of other CPUs: */
- .fill (GDT_SIZE * NR_CPUS) - (gdt_end - cpu_gdt_table)
+ /* GDTs of other CPUs are now dynamically allocated */

- .align L1_CACHE_BYTES
+ /* zero the remaining page */
+ .fill PAGE_SIZE / 8 - GDT_ENTRIES,8,0
+
ENTRY(idt_table)
.rept 256
.quad 0
Index: linux-2.6.15-rc3/arch/x86_64/kernel/setup64.c
===================================================================
--- linux-2.6.15-rc3.orig/arch/x86_64/kernel/setup64.c 2005-12-01 16:19:28.000000000 -0800
+++ linux-2.6.15-rc3/arch/x86_64/kernel/setup64.c 2005-12-01 16:19:29.000000000 -0800
@@ -232,15 +232,15 @@
* and set up the GDT descriptor:
*/
if (cpu) {
- memcpy(cpu_gdt_table[cpu], cpu_gdt_table[0], GDT_SIZE);
+ memcpy(get_cpu_gdt_table(cpu), cpu_gdt_table, GDT_SIZE);
}

cpu_gdt_descr[cpu].size = GDT_SIZE;
- cpu_gdt_descr[cpu].address = (unsigned long)cpu_gdt_table[cpu];
+
asm volatile("lgdt %0" :: "m" (cpu_gdt_descr[cpu]));
asm volatile("lidt %0" :: "m" (idt_descr));

- memcpy(me->thread.tls_array, cpu_gdt_table[cpu], GDT_ENTRY_TLS_ENTRIES * 8);
+ memcpy(me->thread.tls_array, get_cpu_gdt_table(cpu), GDT_ENTRY_TLS_ENTRIES * 8);

/*
* Delete NT
Index: linux-2.6.15-rc3/arch/x86_64/kernel/smpboot.c
===================================================================
--- linux-2.6.15-rc3.orig/arch/x86_64/kernel/smpboot.c 2005-12-01 16:19:28.000000000 -0800
+++ linux-2.6.15-rc3/arch/x86_64/kernel/smpboot.c 2005-12-01 16:19:29.000000000 -0800
@@ -743,6 +743,13 @@
};
DECLARE_WORK(work, do_fork_idle, &c_idle);

+ /* allocate memory for gdts of secondary cpus. Hotplug is considered */
+ if (!cpu_gdt_descr[cpu].address &&
+ !(cpu_gdt_descr[cpu].address = get_zeroed_page(GFP_KERNEL))) {
+ printk("Failed to allocate GDT for CPU %d\n", cpu);
+ return 1;
+ }
+
c_idle.idle = get_idle_for_cpu(cpu);

if (c_idle.idle) {
Index: linux-2.6.15-rc3/arch/x86_64/kernel/suspend.c
===================================================================
--- linux-2.6.15-rc3.orig/arch/x86_64/kernel/suspend.c 2005-12-01 15:49:27.000000000 -0800
+++ linux-2.6.15-rc3/arch/x86_64/kernel/suspend.c 2005-12-01 16:19:29.000000000 -0800
@@ -120,7 +120,7 @@

set_tss_desc(cpu,t); /* This just modifies memory; should not be neccessary. But... This is neccessary, because 386 hardware has concept of busy TSS or some similar stupidity. */

- cpu_gdt_table[cpu][GDT_ENTRY_TSS].type = 9;
+ get_cpu_gdt_table(cpu)[GDT_ENTRY_TSS].type = 9;

syscall_init(); /* This sets MSR_*STAR and related */
load_TR_desc(); /* This does ltr */
Index: linux-2.6.15-rc3/include/asm-x86_64/desc.h
===================================================================
--- linux-2.6.15-rc3.orig/include/asm-x86_64/desc.h 2005-12-01 15:49:27.000000000 -0800
+++ linux-2.6.15-rc3/include/asm-x86_64/desc.h 2005-12-01 16:19:29.000000000 -0800
@@ -25,7 +25,7 @@
unsigned int a,b;
};

-extern struct desc_struct cpu_gdt_table[NR_CPUS][GDT_ENTRIES];
+extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];

enum {
GATE_INTERRUPT = 0xE,
@@ -79,6 +79,9 @@
extern struct gate_struct idt_table[];
extern struct desc_ptr cpu_gdt_descr[];

+/* the cpu gdt accessor */
+#define get_cpu_gdt_table(_cpu) ((struct desc_struct *)cpu_gdt_descr[(_cpu)].address)
+
static inline void _set_gate(void *adr, unsigned type, unsigned long func, unsigned dpl, unsigned ist)
{
struct gate_struct s;
@@ -139,20 +142,20 @@
* -1? seg base+limit should be pointing to the address of the
* last valid byte
*/
- set_tssldt_descriptor(&cpu_gdt_table[cpu][GDT_ENTRY_TSS],
+ set_tssldt_descriptor(&get_cpu_gdt_table(cpu)[GDT_ENTRY_TSS],
(unsigned long)addr, DESC_TSS,
IO_BITMAP_OFFSET + IO_BITMAP_BYTES + sizeof(unsigned long) - 1);
}

static inline void set_ldt_desc(unsigned cpu, void *addr, int size)
{
- set_tssldt_descriptor(&cpu_gdt_table[cpu][GDT_ENTRY_LDT], (unsigned long)addr,
+ set_tssldt_descriptor(&get_cpu_gdt_table(cpu)[GDT_ENTRY_LDT], (unsigned long)addr,
DESC_LDT, size * 8 - 1);
}

static inline void set_seg_base(unsigned cpu, int entry, void *base)
{
- struct desc_struct *d = &cpu_gdt_table[cpu][entry];
+ struct desc_struct *d = &get_cpu_gdt_table(cpu)[entry];
u32 addr = (u32)(u64)base;
BUG_ON((u64)base >> 32);
d->base0 = addr & 0xffff;
@@ -194,7 +197,7 @@

static inline void load_TLS(struct thread_struct *t, unsigned int cpu)
{
- u64 *gdt = (u64 *)(cpu_gdt_table[cpu] + GDT_ENTRY_TLS_MIN);
+ u64 *gdt = (u64 *)(get_cpu_gdt_table(cpu) + GDT_ENTRY_TLS_MIN);
gdt[0] = t->tls_array[0];
gdt[1] = t->tls_array[1];
gdt[2] = t->tls_array[2];
-
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