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

#include <linux/binfmts.h>
#include <linux/elf.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/random.h>
#include <linux/vdso_datastore.h>
#include <vdso/datapage.h>
#include <asm/vdso/vsyscall.h>
#include <asm/alternative.h>
#include <asm/vdso.h>

extern char vdso_start[], vdso_end[];

static int vdso_mremap(const struct vm_special_mapping *sm,
                       struct vm_area_struct *vma)
{
        current->mm->context.vdso_base = vma->vm_start;
        return 0;
}

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

int vdso_getcpu_init(void)
{
        set_tod_programmable_field(smp_processor_id());
        return 0;
}
early_initcall(vdso_getcpu_init); /* Must be called before SMP init */

static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len)
{
        unsigned long vvar_start, vdso_text_start, vdso_text_len;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        int rc;

        BUILD_BUG_ON(VDSO_NR_PAGES != __VDSO_PAGES);
        if (mmap_write_lock_killable(mm))
                return -EINTR;

        vdso_text_len = vdso_end - vdso_start;
        vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0);
        rc = vvar_start;
        if (IS_ERR_VALUE(vvar_start))
                goto out;
        vma = vdso_install_vvar_mapping(mm, vvar_start);
        rc = PTR_ERR(vma);
        if (IS_ERR(vma))
                goto out;
        vdso_text_start = vvar_start + VDSO_NR_PAGES * PAGE_SIZE;
        /* VM_MAYWRITE for COW so gdb can set breakpoints */
        vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
                                       VM_READ|VM_EXEC|VM_SEALED_SYSMAP|
                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                                       &vdso_mapping);
        if (IS_ERR(vma)) {
                do_munmap(mm, vvar_start, PAGE_SIZE, NULL);
                rc = PTR_ERR(vma);
        } else {
                current->mm->context.vdso_base = vdso_text_start;
                rc = 0;
        }
out:
        mmap_write_unlock(mm);
        return rc;
}

static unsigned long vdso_addr(unsigned long start, unsigned long len)
{
        unsigned long addr, end, offset;

        /*
         * Round up the start address. It can start out unaligned as a result
         * of stack start randomization.
         */
        start = PAGE_ALIGN(start);

        /* Round the lowest possible end address up to a PMD boundary. */
        end = (start + len + PMD_SIZE - 1) & PMD_MASK;
        if (end >= VDSO_BASE)
                end = VDSO_BASE;
        end -= len;

        if (end > start) {
                offset = get_random_u32_below(((end - start) >> PAGE_SHIFT) + 1);
                addr = start + (offset << PAGE_SHIFT);
        } else {
                addr = start;
        }
        return addr;
}

unsigned long vdso_text_size(void)
{
        return PAGE_ALIGN(vdso_end - vdso_start);
}

unsigned long vdso_size(void)
{
        return vdso_text_size() + VDSO_NR_PAGES * PAGE_SIZE;
}

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
        unsigned long addr = VDSO_BASE;
        unsigned long size = vdso_size();

        if (current->flags & PF_RANDOMIZE)
                addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size);
        return map_vdso(addr, size);
}

static struct page ** __init vdso_setup_pages(void *start, void *end)
{
        int pages = (end - start) >> PAGE_SHIFT;
        struct page **pagelist;
        int i;

        pagelist = kzalloc_objs(struct page *, pages + 1);
        if (!pagelist)
                panic("%s: Cannot allocate page list for VDSO", __func__);
        for (i = 0; i < pages; i++)
                pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
        return pagelist;
}

static void vdso_apply_alternatives(void)
{
        const struct elf64_shdr *alt, *shdr;
        struct alt_instr *start, *end;
        const struct elf64_hdr *hdr;

        hdr = (struct elf64_hdr *)vdso_start;
        shdr = (void *)hdr + hdr->e_shoff;
        alt = find_section(hdr, shdr, ".altinstructions");
        if (!alt)
                return;
        start = (void *)hdr + alt->sh_offset;
        end = (void *)hdr + alt->sh_offset + alt->sh_size;
        apply_alternatives(start, end);
}

static int __init vdso_init(void)
{
        vdso_apply_alternatives();
        vdso_mapping.pages = vdso_setup_pages(vdso_start, vdso_end);
        return 0;
}
arch_initcall(vdso_init);