source: mainline/kernel/arch/ia32/src/userspace.c

/*
 * Copyright (c) 2005 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup kernel_ia32
 * @{
 */
/** @file
 */

#include <userspace.h>
#include <arch/pm.h>
#include <stdbool.h>
#include <stdint.h>
#include <arch.h>
#include <mm/as.h>
#include <arch/cpu.h>
#include <arch/asm.h>

uintptr_t arch_get_initial_sp(uintptr_t stack_base, uintptr_t stack_size)
{
        return stack_base + stack_size;
}

/** Enter userspace
 *
 * Change CPU protection level to 3, enter userspace.
 *
 */
void userspace(uintptr_t pc, uintptr_t sp)
{
        uint32_t eflags = read_eflags();

        asm volatile (
            /* Set up GS register (virtual register segment) */
            "movl %[vreg_des], %%gs\n"

            "pushl %[udata_des]\n"
            "pushl %[stack_top]\n"
            "pushl %[eflags]\n"
            "pushl %[utext_des]\n"
            "pushl %[entry]\n"

            /* %edi is defined to hold pcb_ptr - set it to 0 */
            "xorl %%edi, %%edi\n"

            "iret\n"
            :
            : [eflags_mask] "i" (~EFLAGS_NT),
              [udata_des] "i" (GDT_SELECTOR(UDATA_DES) | PL_USER),
              [stack_top] "r" (sp),
              [eflags] "r" ((eflags & ~(EFLAGS_NT)) | EFLAGS_IF),
              [utext_des] "i" (GDT_SELECTOR(UTEXT_DES) | PL_USER),
              [entry] "r" (pc),
              [vreg_des] "r" (GDT_SELECTOR(VREG_DES))
            : "eax");

        unreachable();
}

/** @}
 */