// 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/compat.h>
#include <linux/elf.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/time_namespace.h>
#include <vdso/datapage.h>
#include <asm/vdso.h>

extern char vdso64_start[], vdso64_end[];
extern char vdso32_start[], vdso32_end[];

static struct vm_special_mapping vvar_mapping;

static union {
        struct vdso_data        data[CS_BASES];
        u8                      page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;

struct vdso_data *vdso_data = vdso_data_store.data;

enum vvar_pages {
        VVAR_DATA_PAGE_OFFSET,
        VVAR_TIMENS_PAGE_OFFSET,
        VVAR_NR_PAGES,
};

#ifdef CONFIG_TIME_NS
struct vdso_data *arch_get_vdso_data(void *vvar_page)
{
        return (struct vdso_data *)(vvar_page);
}

static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
        if (likely(vma->vm_mm == current->mm))
                return current->nsproxy->time_ns->vvar_page;
        /*
         * VM_PFNMAP | VM_IO protect .fault() handler from being called
         * through interfaces like /proc/$pid/mem or
         * process_vm_{readv,writev}() as long as there's no .access()
         * in special_mapping_vmops().
         * For more details check_vma_flags() and __access_remote_vm()
         */
        WARN(1, "vvar_page accessed remotely");
        return NULL;
}

/*
 * The VVAR page layout depends on whether a task belongs to the root or
 * non-root time namespace. Whenever a task changes its namespace, the VVAR
 * page tables are cleared and then they will be re-faulted with a
 * corresponding layout.
 * See also the comment near timens_setup_vdso_data() for details.
 */
int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
{
        struct mm_struct *mm = task->mm;
        struct vm_area_struct *vma;

        mmap_read_lock(mm);
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
                unsigned long size = vma->vm_end - vma->vm_start;

                if (!vma_is_special_mapping(vma, &vvar_mapping))
                        continue;
                zap_page_range(vma, vma->vm_start, size);
                break;
        }
        mmap_read_unlock(mm);
        return 0;
}
#else
static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
        return NULL;
}
#endif

static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
                             struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page *timens_page = find_timens_vvar_page(vma);
        unsigned long addr, pfn;
        vm_fault_t err;

        switch (vmf->pgoff) {
        case VVAR_DATA_PAGE_OFFSET:
                pfn = virt_to_pfn(vdso_data);
                if (timens_page) {
                        /*
                         * Fault in VVAR page too, since it will be accessed
                         * to get clock data anyway.
                         */
                        addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
                        err = vmf_insert_pfn(vma, addr, pfn);
                        if (unlikely(err & VM_FAULT_ERROR))
                                return err;
                        pfn = page_to_pfn(timens_page);
                }
                break;
#ifdef CONFIG_TIME_NS
        case VVAR_TIMENS_PAGE_OFFSET:
                /*
                 * If a task belongs to a time namespace then a namespace
                 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
                 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
                 * offset.
                 * See also the comment near timens_setup_vdso_data().
                 */
                if (!timens_page)
                        return VM_FAULT_SIGBUS;
                pfn = virt_to_pfn(vdso_data);
                break;
#endif /* CONFIG_TIME_NS */
        default:
                return VM_FAULT_SIGBUS;
        }
        return vmf_insert_pfn(vma, vmf->address, pfn);
}

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 vvar_mapping = {
        .name = "[vvar]",
        .fault = vvar_fault,
};

static struct vm_special_mapping vdso64_mapping = {
        .name = "[vdso]",
        .mremap = vdso_mremap,
};

static struct vm_special_mapping vdso32_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 */

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
        unsigned long vdso_text_len, vdso_mapping_len;
        unsigned long vvar_start, vdso_text_start;
        struct vm_special_mapping *vdso_mapping;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        int rc;

        BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
        if (mmap_write_lock_killable(mm))
                return -EINTR;

        if (is_compat_task()) {
                vdso_text_len = vdso32_end - vdso32_start;
                vdso_mapping = &vdso32_mapping;
        } else {
                vdso_text_len = vdso64_end - vdso64_start;
                vdso_mapping = &vdso64_mapping;
        }
        vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
        vvar_start = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
        rc = vvar_start;
        if (IS_ERR_VALUE(vvar_start))
                goto out;
        vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE,
                                       VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
                                       VM_PFNMAP,
                                       &vvar_mapping);
        rc = PTR_ERR(vma);
        if (IS_ERR(vma))
                goto out;
        vdso_text_start = vvar_start + VVAR_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_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 struct page ** __init vdso_setup_pages(void *start, void *end)
{
        int pages = (end - start) >> PAGE_SHIFT;
        struct page **pagelist;
        int i;

        pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
        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 int __init vdso_init(void)
{
        vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end);
        if (IS_ENABLED(CONFIG_COMPAT))
                vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end);
        return 0;
}
arch_initcall(vdso_init);