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Commit 72c511dd authored by Brian Gerst's avatar Brian Gerst Committed by H. Peter Anvin
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x86-32, asm: Directly access per-cpu GDT 



Use a direct per-cpu reference for the GDT instead of using a scratch
register.

Signed-off-by: default avatarBrian Gerst <brgerst@gmail.com>
LKML-Reference: <1280594903-6341-2-git-send-email-brgerst@gmail.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent c15a5958

arch/x86/kernel/entry_32.S

+5 −6
Original line number Diff line number Diff line
@@ -611,14 +611,14 @@ ldt_ss: 
 * compensating for the offset by changing to the ESPFIX segment with

 * a base address that matches for the difference.

 */

#define GDT_ESPFIX_SS PER_CPU_VAR(gdt_page) + (GDT_ENTRY_ESPFIX_SS * 8)

	mov %esp, %edx			/* load kernel esp */

	mov PT_OLDESP(%esp), %eax	/* load userspace esp */

	mov %dx, %ax			/* eax: new kernel esp */

	sub %eax, %edx			/* offset (low word is 0) */

	PER_CPU(gdt_page, %ebx)

	shr $16, %edx

	mov %dl, GDT_ENTRY_ESPFIX_SS * 8 + 4(%ebx) /* bits 16..23 */

	mov %dh, GDT_ENTRY_ESPFIX_SS * 8 + 7(%ebx) /* bits 24..31 */

	mov %dl, GDT_ESPFIX_SS + 4 /* bits 16..23 */

	mov %dh, GDT_ESPFIX_SS + 7 /* bits 24..31 */

	pushl $__ESPFIX_SS

	CFI_ADJUST_CFA_OFFSET 4

	push %eax			/* new kernel esp */
@@ -791,9 +791,8 @@ ptregs_clone: 
 * normal stack and adjusts ESP with the matching offset.

 */

	/* fixup the stack */

	PER_CPU(gdt_page, %ebx)

	mov GDT_ENTRY_ESPFIX_SS * 8 + 4(%ebx), %al /* bits 16..23 */

	mov GDT_ENTRY_ESPFIX_SS * 8 + 7(%ebx), %ah /* bits 24..31 */

	mov GDT_ESPFIX_SS + 4, %al /* bits 16..23 */

	mov GDT_ESPFIX_SS + 7, %ah /* bits 24..31 */

	shl $16, %eax

	addl %esp, %eax			/* the adjusted stack pointer */

	pushl $__KERNEL_DS