// SPDX-License-Identifier: GPL-2.0-only
/*
 * Adapted from arm64 version.
 *
 * Copyright (C) 2012 ARM Limited
 * Copyright (C) 2015 Mentor Graphics Corporation.
 */

#include <linux/cache.h>
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/of.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <asm/arch_timer.h>
#include <asm/barrier.h>
#include <asm/cacheflush.h>
#include <asm/page.h>
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>
#include <clocksource/arm_arch_timer.h>
#include <vdso/helpers.h>
#include <vdso/vsyscall.h>

#define MAX_SYMNAME     64

static struct page **vdso_text_pagelist;

extern char vdso_start[], vdso_end[];

/* Total number of pages needed for the data and text portions of the VDSO. */
unsigned int vdso_total_pages __ro_after_init;

/*
 * The VDSO data page.
 */
static union vdso_data_store vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = vdso_data_store.data;

static struct page *vdso_data_page __ro_after_init;
static const struct vm_special_mapping vdso_data_mapping = {
        .name = "[vvar]",
        .pages = &vdso_data_page,
};

static int vdso_mremap(const struct vm_special_mapping *sm,
                struct vm_area_struct *new_vma)
{
        current->mm->context.vdso = new_vma->vm_start;

        return 0;
}

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

struct elfinfo {
        Elf32_Ehdr      *hdr;           /* ptr to ELF */
        Elf32_Sym       *dynsym;        /* ptr to .dynsym section */
        unsigned long   dynsymsize;     /* size of .dynsym section */
        char            *dynstr;        /* ptr to .dynstr section */
};

/* Cached result of boot-time check for whether the arch timer exists,
 * and if so, whether the virtual counter is useable.
 */
bool cntvct_ok __ro_after_init;

static bool __init cntvct_functional(void)
{
        struct device_node *np;
        bool ret = false;

        if (!IS_ENABLED(CONFIG_ARM_ARCH_TIMER))
                goto out;

        /* The arm_arch_timer core should export
         * arch_timer_use_virtual or similar so we don't have to do
         * this.
         */
        np = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
        if (!np)
                np = of_find_compatible_node(NULL, NULL, "arm,armv8-timer");
        if (!np)
                goto out_put;

        if (of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
                goto out_put;

        ret = true;

out_put:
        of_node_put(np);
out:
        return ret;
}

static void * __init find_section(Elf32_Ehdr *ehdr, const char *name,
                                  unsigned long *size)
{
        Elf32_Shdr *sechdrs;
        unsigned int i;
        char *secnames;

        /* Grab section headers and strings so we can tell who is who */
        sechdrs = (void *)ehdr + ehdr->e_shoff;
        secnames = (void *)ehdr + sechdrs[ehdr->e_shstrndx].sh_offset;

        /* Find the section they want */
        for (i = 1; i < ehdr->e_shnum; i++) {
                if (strcmp(secnames + sechdrs[i].sh_name, name) == 0) {
                        if (size)
                                *size = sechdrs[i].sh_size;
                        return (void *)ehdr + sechdrs[i].sh_offset;
                }
        }

        if (size)
                *size = 0;
        return NULL;
}

static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
{
        unsigned int i;

        for (i = 0; i < (lib->dynsymsize / sizeof(Elf32_Sym)); i++) {
                char name[MAX_SYMNAME], *c;

                if (lib->dynsym[i].st_name == 0)
                        continue;
                strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
                        MAX_SYMNAME);
                c = strchr(name, '@');
                if (c)
                        *c = 0;
                if (strcmp(symname, name) == 0)
                        return &lib->dynsym[i];
        }
        return NULL;
}

static void __init vdso_nullpatch_one(struct elfinfo *lib, const char *symname)
{
        Elf32_Sym *sym;

        sym = find_symbol(lib, symname);
        if (!sym)
                return;

        sym->st_name = 0;
}

static void __init patch_vdso(void *ehdr)
{
        struct elfinfo einfo;

        einfo = (struct elfinfo) {
                .hdr = ehdr,
        };

        einfo.dynsym = find_section(einfo.hdr, ".dynsym", &einfo.dynsymsize);
        einfo.dynstr = find_section(einfo.hdr, ".dynstr", NULL);

        /* If the virtual counter is absent or non-functional we don't
         * want programs to incur the slight additional overhead of
         * dispatching through the VDSO only to fall back to syscalls.
         */
        if (!cntvct_ok) {
                vdso_nullpatch_one(&einfo, "__vdso_gettimeofday");
                vdso_nullpatch_one(&einfo, "__vdso_clock_gettime");
                vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64");
        }
}

static int __init vdso_init(void)
{
        unsigned int text_pages;
        int i;

        if (memcmp(vdso_start, "\177ELF", 4)) {
                pr_err("VDSO is not a valid ELF object!\n");
                return -ENOEXEC;
        }

        text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;

        /* Allocate the VDSO text pagelist */
        vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *),
                                     GFP_KERNEL);
        if (vdso_text_pagelist == NULL)
                return -ENOMEM;

        /* Grab the VDSO data page. */
        vdso_data_page = virt_to_page(vdso_data);

        /* Grab the VDSO text pages. */
        for (i = 0; i < text_pages; i++) {
                struct page *page;

                page = virt_to_page(vdso_start + i * PAGE_SIZE);
                vdso_text_pagelist[i] = page;
        }

        vdso_text_mapping.pages = vdso_text_pagelist;

        vdso_total_pages = 1; /* for the data/vvar page */
        vdso_total_pages += text_pages;

        cntvct_ok = cntvct_functional();

        patch_vdso(vdso_start);

        return 0;
}
arch_initcall(vdso_init);

static int install_vvar(struct mm_struct *mm, unsigned long addr)
{
        struct vm_area_struct *vma;

        vma = _install_special_mapping(mm, addr, PAGE_SIZE,
                                       VM_READ | VM_MAYREAD,
                                       &vdso_data_mapping);

        return PTR_ERR_OR_ZERO(vma);
}

/* assumes mmap_lock is write-locked */
void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
{
        struct vm_area_struct *vma;
        unsigned long len;

        mm->context.vdso = 0;

        if (vdso_text_pagelist == NULL)
                return;

        if (install_vvar(mm, addr))
                return;

        /* Account for vvar page. */
        addr += PAGE_SIZE;
        len = (vdso_total_pages - 1) << PAGE_SHIFT;

        vma = _install_special_mapping(mm, addr, len,
                VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
                &vdso_text_mapping);

        if (!IS_ERR(vma))
                mm->context.vdso = addr;
}