/*
 * Set up the VMAs to tell the VM about the vDSO.
 * Copyright 2007 Andi Kleen, SUSE Labs.
 * Subject to the GPL, v.2
 */

/*
 * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
 */

#include <linux/mm.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <asm/vdso.h>
#include <asm/vvar.h>
#include <asm/page.h>

unsigned int __read_mostly vdso_enabled = 1;

static struct vm_special_mapping vvar_mapping = {
        .name = "[vvar]"
};

#ifdef  CONFIG_SPARC64
static struct vm_special_mapping vdso_mapping64 = {
        .name = "[vdso]"
};
#endif

#ifdef CONFIG_COMPAT
static struct vm_special_mapping vdso_mapping32 = {
        .name = "[vdso]"
};
#endif

struct vvar_data *vvar_data;

#define SAVE_INSTR_SIZE 4

/*
 * Allocate pages for the vdso and vvar, and copy in the vdso text from the
 * kernel image.
 */
int __init init_vdso_image(const struct vdso_image *image,
                struct vm_special_mapping *vdso_mapping)
{
        int i;
        struct page *dp, **dpp = NULL;
        int dnpages = 0;
        struct page *cp, **cpp = NULL;
        int cnpages = (image->size) / PAGE_SIZE;

        /*
         * First, the vdso text.  This is initialied data, an integral number of
         * pages long.
         */
        if (WARN_ON(image->size % PAGE_SIZE != 0))
                goto oom;

        cpp = kcalloc(cnpages, sizeof(struct page *), GFP_KERNEL);
        vdso_mapping->pages = cpp;

        if (!cpp)
                goto oom;

        if (vdso_fix_stick) {
                /*
                 * If the system uses %tick instead of %stick, patch the VDSO
                 * with instruction reading %tick instead of %stick.
                 */
                unsigned int j, k = SAVE_INSTR_SIZE;
                unsigned char *data = image->data;

                for (j = image->sym_vread_tick_patch_start;
                     j < image->sym_vread_tick_patch_end; j++) {

                        data[image->sym_vread_tick + k] = data[j];
                        k++;
                }
        }

        for (i = 0; i < cnpages; i++) {
                cp = alloc_page(GFP_KERNEL);
                if (!cp)
                        goto oom;
                cpp[i] = cp;
                copy_page(page_address(cp), image->data + i * PAGE_SIZE);
        }

        /*
         * Now the vvar page.  This is uninitialized data.
         */

        if (vvar_data == NULL) {
                dnpages = (sizeof(struct vvar_data) / PAGE_SIZE) + 1;
                if (WARN_ON(dnpages != 1))
                        goto oom;
                dpp = kcalloc(dnpages, sizeof(struct page *), GFP_KERNEL);
                vvar_mapping.pages = dpp;

                if (!dpp)
                        goto oom;

                dp = alloc_page(GFP_KERNEL);
                if (!dp)
                        goto oom;

                dpp[0] = dp;
                vvar_data = page_address(dp);
                memset(vvar_data, 0, PAGE_SIZE);

                vvar_data->seq = 0;
        }

        return 0;
 oom:
        if (cpp != NULL) {
                for (i = 0; i < cnpages; i++) {
                        if (cpp[i] != NULL)
                                __free_page(cpp[i]);
                }
                kfree(cpp);
                vdso_mapping->pages = NULL;
        }

        if (dpp != NULL) {
                for (i = 0; i < dnpages; i++) {
                        if (dpp[i] != NULL)
                                __free_page(dpp[i]);
                }
                kfree(dpp);
                vvar_mapping.pages = NULL;
        }

        pr_warn("Cannot allocate vdso\n");
        vdso_enabled = 0;
        return -ENOMEM;
}

static int __init init_vdso(void)
{
        int err = 0;
#ifdef CONFIG_SPARC64
        err = init_vdso_image(&vdso_image_64_builtin, &vdso_mapping64);
        if (err)
                return err;
#endif

#ifdef CONFIG_COMPAT
        err = init_vdso_image(&vdso_image_32_builtin, &vdso_mapping32);
#endif
        return err;

}
subsys_initcall(init_vdso);

struct linux_binprm;

/* Shuffle the vdso up a bit, randomly. */
static unsigned long vdso_addr(unsigned long start, unsigned int len)
{
        unsigned int offset;

        /* This loses some more bits than a modulo, but is cheaper */
        offset = get_random_int() & (PTRS_PER_PTE - 1);
        return start + (offset << PAGE_SHIFT);
}

static int map_vdso(const struct vdso_image *image,
                struct vm_special_mapping *vdso_mapping)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long text_start, addr = 0;
        int ret = 0;

        down_write(&mm->mmap_sem);

        /*
         * First, get an unmapped region: then randomize it, and make sure that
         * region is free.
         */
        if (current->flags & PF_RANDOMIZE) {
                addr = get_unmapped_area(NULL, 0,
                                         image->size - image->sym_vvar_start,
                                         0, 0);
                if (IS_ERR_VALUE(addr)) {
                        ret = addr;
                        goto up_fail;
                }
                addr = vdso_addr(addr, image->size - image->sym_vvar_start);
        }
        addr = get_unmapped_area(NULL, addr,
                                 image->size - image->sym_vvar_start, 0, 0);
        if (IS_ERR_VALUE(addr)) {
                ret = addr;
                goto up_fail;
        }

        text_start = addr - image->sym_vvar_start;
        current->mm->context.vdso = (void __user *)text_start;

        /*
         * MAYWRITE to allow gdb to COW and set breakpoints
         */
        vma = _install_special_mapping(mm,
                                       text_start,
                                       image->size,
                                       VM_READ|VM_EXEC|
                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                                       vdso_mapping);

        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                goto up_fail;
        }

        vma = _install_special_mapping(mm,
                                       addr,
                                       -image->sym_vvar_start,
                                       VM_READ|VM_MAYREAD,
                                       &vvar_mapping);

        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);
                do_munmap(mm, text_start, image->size, NULL);
        }

up_fail:
        if (ret)
                current->mm->context.vdso = NULL;

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

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{

        if (!vdso_enabled)
                return 0;

#if defined CONFIG_COMPAT
        if (!(is_32bit_task()))
                return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
        else
                return map_vdso(&vdso_image_32_builtin, &vdso_mapping32);
#else
        return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
#endif

}

static __init int vdso_setup(char *s)
{
        int err;
        unsigned long val;

        err = kstrtoul(s, 10, &val);
        vdso_enabled = val;
        return err;
}
__setup("vdso=", vdso_setup);