vdso.c

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/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2009, 2010 Cavium Networks, Inc.
 */


#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/binfmts.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/unistd.h>

#include <asm/vdso.h>
#include <asm/uasm.h>

/*
 * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
 */
#define __NR_O32_sigreturn      4119
#define __NR_O32_rt_sigreturn       4193
#define __NR_N32_rt_sigreturn       6211

static struct page *vdso_page;

static void __init install_trampoline(u32 *tramp, unsigned int sigreturn)
{
    uasm_i_addiu(&tramp, 2, 0, sigreturn);  /* li v0, sigreturn */
    uasm_i_syscall(&tramp, 0);
}

static int __init init_vdso(void)
{
    struct mips_vdso *vdso;

    vdso_page = alloc_page(GFP_KERNEL);
    if (!vdso_page)
        panic("Cannot allocate vdso");

    vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
    if (!vdso)
        panic("Cannot map vdso");
    clear_page(vdso);

    install_trampoline(vdso->rt_signal_trampoline, __NR_rt_sigreturn);
#ifdef CONFIG_32BIT
    install_trampoline(vdso->signal_trampoline, __NR_sigreturn);
#else
    install_trampoline(vdso->n32_rt_signal_trampoline,
               __NR_N32_rt_sigreturn);
    install_trampoline(vdso->o32_signal_trampoline, __NR_O32_sigreturn);
    install_trampoline(vdso->o32_rt_signal_trampoline,
               __NR_O32_rt_sigreturn);
#endif

    vunmap(vdso);

    return 0;
}
subsys_initcall(init_vdso);

static unsigned long vdso_addr(unsigned long start)
{
    return STACK_TOP;
}

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
    int ret;
    unsigned long addr;
    struct mm_struct *mm = current->mm;

    down_write(&mm->mmap_sem);

    addr = vdso_addr(mm->start_stack);

    addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, 0);
    if (IS_ERR_VALUE(addr)) {
        ret = addr;
        goto up_fail;
    }

    ret = install_special_mapping(mm, addr, PAGE_SIZE,
                      VM_READ|VM_EXEC|
                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                      &vdso_page);

    if (ret)
        goto up_fail;

    mm->context.vdso = (void *)addr;

up_fail:
    up_write(&mm->mmap_sem);
    return ret;
}

const char *arch_vma_name(struct vm_area_struct *vma)
{
    if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
        return "[vdso]";
    return NULL;
}