// SPDX-License-Identifier: GPL-2.0
/*
 * vdso setup for s390
 *
 *  Copyright IBM Corp. 2008
 *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
 */

#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/memblock.h>
#include <linux/compat.h>
#include <linux/binfmts.h>
#include <vdso/datapage.h>
#include <asm/asm-offsets.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/sections.h>
#include <asm/vdso.h>
#include <asm/facility.h>

extern char vdso64_start, vdso64_end;
static void *vdso64_kbase = &vdso64_start;
static unsigned int vdso64_pages;
static struct page **vdso64_pagelist;

/*
 * Should the kernel map a VDSO page into processes and pass its
 * address down to glibc upon exec()?
 */
unsigned int __read_mostly vdso_enabled = 1;

static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
                      struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page **vdso_pagelist;
        unsigned long vdso_pages;

        vdso_pagelist = vdso64_pagelist;
        vdso_pages = vdso64_pages;

        if (vmf->pgoff >= vdso_pages)
                return VM_FAULT_SIGBUS;

        vmf->page = vdso_pagelist[vmf->pgoff];
        get_page(vmf->page);
        return 0;
}

static int vdso_mremap(const struct vm_special_mapping *sm,
                       struct vm_area_struct *vma)
{
        unsigned long vdso_pages;

        vdso_pages = vdso64_pages;

        if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
                return -EINVAL;

        if (WARN_ON_ONCE(current->mm != vma->vm_mm))
                return -EFAULT;

        current->mm->context.vdso_base = vma->vm_start;
        return 0;
}

static const struct vm_special_mapping vdso_mapping = {
        .name = "[vdso]",
        .fault = vdso_fault,
        .mremap = vdso_mremap,
};

static int __init vdso_setup(char *str)
{
        bool enabled;

        if (!kstrtobool(str, &enabled))
                vdso_enabled = enabled;
        return 1;
}
__setup("vdso=", vdso_setup);

/*
 * The vdso data page
 */
static union {
        struct vdso_data        data;
        u8                      page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = (struct vdso_data *)&vdso_data_store.data;
/*
 * Allocate/free per cpu vdso data.
 */
#define SEGMENT_ORDER   2

int vdso_alloc_per_cpu(struct lowcore *lowcore)
{
        unsigned long segment_table, page_table, page_frame;
        struct vdso_per_cpu_data *vd;

        segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
        page_table = get_zeroed_page(GFP_KERNEL);
        page_frame = get_zeroed_page(GFP_KERNEL);
        if (!segment_table || !page_table || !page_frame)
                goto out;
        arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
        arch_set_page_dat(virt_to_page(page_table), 0);

        /* Initialize per-cpu vdso data page */
        vd = (struct vdso_per_cpu_data *) page_frame;
        vd->cpu_nr = lowcore->cpu_nr;
        vd->node_id = cpu_to_node(vd->cpu_nr);

        /* Set up page table for the vdso address space */
        memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
        memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);

        *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
        *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;

        lowcore->vdso_asce = segment_table +
                _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
        lowcore->vdso_per_cpu_data = page_frame;

        return 0;

out:
        free_page(page_frame);
        free_page(page_table);
        free_pages(segment_table, SEGMENT_ORDER);
        return -ENOMEM;
}

void vdso_free_per_cpu(struct lowcore *lowcore)
{
        unsigned long segment_table, page_table, page_frame;

        segment_table = lowcore->vdso_asce & PAGE_MASK;
        page_table = *(unsigned long *) segment_table;
        page_frame = *(unsigned long *) page_table;

        free_page(page_frame);
        free_page(page_table);
        free_pages(segment_table, SEGMENT_ORDER);
}

/*
 * This is called from binfmt_elf, we create the special vma for the
 * vDSO and insert it into the mm struct tree
 */
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long vdso_pages;
        unsigned long vdso_base;
        int rc;

        if (!vdso_enabled)
                return 0;

        if (is_compat_task())
                return 0;

        vdso_pages = vdso64_pages;
        /*
         * vDSO has a problem and was disabled, just don't "enable" it for
         * the process
         */
        if (vdso_pages == 0)
                return 0;

        /*
         * pick a base address for the vDSO in process space. We try to put
         * it at vdso_base which is the "natural" base for it, but we might
         * fail and end up putting it elsewhere.
         */
        if (mmap_write_lock_killable(mm))
                return -EINTR;
        vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
        if (IS_ERR_VALUE(vdso_base)) {
                rc = vdso_base;
                goto out_up;
        }

        /*
         * our vma flags don't have VM_WRITE so by default, the process
         * isn't allowed to write those pages.
         * gdb can break that with ptrace interface, and thus trigger COW
         * on those pages but it's then your responsibility to never do that
         * on the "data" page of the vDSO or you'll stop getting kernel
         * updates and your nice userland gettimeofday will be totally dead.
         * It's fine to use that for setting breakpoints in the vDSO code
         * pages though.
         */
        vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
                                       VM_READ|VM_EXEC|
                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                                       &vdso_mapping);
        if (IS_ERR(vma)) {
                rc = PTR_ERR(vma);
                goto out_up;
        }

        current->mm->context.vdso_base = vdso_base;
        rc = 0;

out_up:
        mmap_write_unlock(mm);
        return rc;
}

static int __init vdso_init(void)
{
        int i;

        /* Calculate the size of the 64 bit vDSO */
        vdso64_pages = ((&vdso64_end - &vdso64_start
                         + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;

        /* Make sure pages are in the correct state */
        vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
                                  GFP_KERNEL);
        BUG_ON(vdso64_pagelist == NULL);
        for (i = 0; i < vdso64_pages - 1; i++) {
                struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
                get_page(pg);
                vdso64_pagelist[i] = pg;
        }
        vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
        vdso64_pagelist[vdso64_pages] = NULL;
        if (vdso_alloc_per_cpu(&S390_lowcore))
                BUG();

        get_page(virt_to_page(vdso_data));

        return 0;
}
early_initcall(vdso_init);