/*
 * Set up the VMAs to tell the VM about the vDSO.
 * Copyright 2007 Andi Kleen, SUSE Labs.
 * Subject to the GPL, v.2
 */
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include <asm/page.h>

unsigned int __read_mostly vdso_enabled = 1;

extern char vdso_start[], vdso_end[];
extern unsigned short vdso_sync_cpuid;

extern struct page *vdso_pages[];
static unsigned vdso_size;

#ifdef CONFIG_X86_X32_ABI
extern char vdsox32_start[], vdsox32_end[];
extern struct page *vdsox32_pages[];
static unsigned vdsox32_size;

static void __init patch_vdsox32(void *vdso, size_t len)
{
        Elf32_Ehdr *hdr = vdso;
        Elf32_Shdr *sechdrs, *alt_sec = 0;
        char *secstrings;
        void *alt_data;
        int i;

        BUG_ON(len < sizeof(Elf32_Ehdr));
        BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);

        sechdrs = (void *)hdr + hdr->e_shoff;
        secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

        for (i = 1; i < hdr->e_shnum; i++) {
                Elf32_Shdr *shdr = &sechdrs[i];
                if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
                        alt_sec = shdr;
                        goto found;
                }
        }

        /* If we get here, it's probably a bug. */
        pr_warning("patch_vdsox32: .altinstructions not found\n");
        return;  /* nothing to patch */

found:
        alt_data = (void *)hdr + alt_sec->sh_offset;
        apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
}
#endif

static void __init patch_vdso64(void *vdso, size_t len)
{
        Elf64_Ehdr *hdr = vdso;
        Elf64_Shdr *sechdrs, *alt_sec = 0;
        char *secstrings;
        void *alt_data;
        int i;

        BUG_ON(len < sizeof(Elf64_Ehdr));
        BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);

        sechdrs = (void *)hdr + hdr->e_shoff;
        secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

        for (i = 1; i < hdr->e_shnum; i++) {
                Elf64_Shdr *shdr = &sechdrs[i];
                if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
                        alt_sec = shdr;
                        goto found;
                }
        }

        /* If we get here, it's probably a bug. */
        pr_warning("patch_vdso64: .altinstructions not found\n");
        return;  /* nothing to patch */

found:
        alt_data = (void *)hdr + alt_sec->sh_offset;
        apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
}

static int __init init_vdso(void)
{
        int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
        int i;

        patch_vdso64(vdso_start, vdso_end - vdso_start);

        vdso_size = npages << PAGE_SHIFT;
        for (i = 0; i < npages; i++)
                vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);

#ifdef CONFIG_X86_X32_ABI
        patch_vdsox32(vdsox32_start, vdsox32_end - vdsox32_start);
        npages = (vdsox32_end - vdsox32_start + PAGE_SIZE - 1) / PAGE_SIZE;
        vdsox32_size = npages << PAGE_SHIFT;
        for (i = 0; i < npages; i++)
                vdsox32_pages[i] = virt_to_page(vdsox32_start + i*PAGE_SIZE);
#endif

        return 0;
}
subsys_initcall(init_vdso);

struct linux_binprm;

/* 
 * Put the vdso above the (randomized) stack with another randomized
 * offset.  This way there is no hole in the middle of address space.
 * To save memory make sure it is still in the same PTE as the stack
 * top.  This doesn't give that many random bits.
 *
 * Note that this algorithm is imperfect: the distribution of the vdso
 * start address within a PMD is biased toward the end.
 *
 * Only used for the 64-bit and x32 vdsos.
 */
static unsigned long vdso_addr(unsigned long start, unsigned len)
{
        unsigned long addr, end;
        unsigned 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 >= TASK_SIZE_MAX)
                end = TASK_SIZE_MAX;
        end -= len;

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

        /*
         * Forcibly align the final address in case we have a hardware
         * issue that requires alignment for performance reasons.
         */
        addr = align_vdso_addr(addr);

        return addr;
}

/* Setup a VMA at program startup for the vsyscall page.
   Not called for compat tasks */
static int setup_additional_pages(struct linux_binprm *bprm,
                                  int uses_interp,
                                  struct page **pages,
                                  unsigned size)
{
        struct mm_struct *mm = current->mm;
        unsigned long addr;
        int ret;

        if (!vdso_enabled)
                return 0;

        down_write(&mm->mmap_sem);
        addr = vdso_addr(mm->start_stack, size);
        addr = get_unmapped_area(NULL, addr, size, 0, 0);
        if (IS_ERR_VALUE(addr)) {
                ret = addr;
                goto up_fail;
        }

        current->mm->context.vdso = (void *)addr;

        ret = install_special_mapping(mm, addr, size,
                                      VM_READ|VM_EXEC|
                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
                                      pages);
        if (ret) {
                current->mm->context.vdso = NULL;
                goto up_fail;
        }

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

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
        return setup_additional_pages(bprm, uses_interp, vdso_pages,
                                      vdso_size);
}

#ifdef CONFIG_X86_X32_ABI
int x32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
        return setup_additional_pages(bprm, uses_interp, vdsox32_pages,
                                      vdsox32_size);
}
#endif

static __init int vdso_setup(char *s)
{
        vdso_enabled = simple_strtoul(s, NULL, 0);
        return 0;
}
__setup("vdso=", vdso_setup);