datapage.s

linux内核源码

/*
 * Access to the shared data page by the vDSO & syscall map
 *
 * Copyright (C) 2004 Benjamin Herrenschmuidt ([e-mail]), IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>
#include <asm/vdso.h>

	.text
V_FUNCTION_BEGIN(__get_datapage)
  .cfi_startproc
	/* We don't want that exposed or overridable as we want other objects
	 * to be able to bl directly to here
	 */
	.protected __get_datapage
	.hidden __get_datapage

	mflr	r0
  .cfi_register lr,r0

	bcl	20,31,1f
	.global	__kernel_datapage_offset;
__kernel_datapage_offset:
	.long	0
1:
	mflr	r3
	mtlr	r0
	lwz	r0,0(r3)
	add	r3,r0,r3
	blr
  .cfi_endproc
V_FUNCTION_END(__get_datapage)

/*
 * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
 *
 * returns a pointer to the syscall map. the map is agnostic to the
 * size of "long", unlike kernel bitops, it stores bits from top to
 * bottom so that memory actually contains a linear bitmap
 * check for syscall N by testing bit (0x80000000 >> (N & 0x1f)) of
 * 32 bits int at N >> 5.
 */
V_FUNCTION_BEGIN(__kernel_get_syscall_map)
  .cfi_startproc
	mflr	r12
  .cfi_register lr,r12
	mr	r4,r3
	bl	__get_datapage@local
	mtlr	r12
	addi	r3,r3,CFG_SYSCALL_MAP32
	cmpli	cr0,r4,0
	beqlr
	li	r0,__NR_syscalls
	stw	r0,0(r4)
	crclr	cr0*4+so
	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_get_syscall_map)

/*
 * void unsigned long long  __kernel_get_tbfreq(void);
 *
 * returns the timebase frequency in HZ
 */
V_FUNCTION_BEGIN(__kernel_get_tbfreq)
  .cfi_startproc
	mflr	r12
  .cfi_register lr,r12
	bl	__get_datapage@local
	lwz	r4,(CFG_TB_TICKS_PER_SEC + 4)(r3)
	lwz	r3,CFG_TB_TICKS_PER_SEC(r3)
	mtlr	r12
	crclr	cr0*4+so
	blr
  .cfi_endproc
V_FUNCTION_END(__kernel_get_tbfreq)