dump_pagetables.c

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#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <asm/sections.h>
#include <asm/pgtable.h>

static unsigned long max_addr;

struct addr_marker {
    unsigned long start_address;
    const char *name;
};

enum address_markers_idx {
    IDENTITY_NR = 0,
    KERNEL_START_NR,
    KERNEL_END_NR,
    VMEMMAP_NR,
    VMALLOC_NR,
#ifdef CONFIG_64BIT
    MODULES_NR,
#endif
};

static struct addr_marker address_markers[] = {
    [IDENTITY_NR]     = {0, "Identity Mapping"},
    [KERNEL_START_NR] = {(unsigned long)&_stext, "Kernel Image Start"},
    [KERNEL_END_NR]   = {(unsigned long)&_end, "Kernel Image End"},
    [VMEMMAP_NR]      = {0, "vmemmap Area"},
    [VMALLOC_NR]      = {0, "vmalloc Area"},
#ifdef CONFIG_64BIT
    [MODULES_NR]      = {0, "Modules Area"},
#endif
    { -1, NULL }
};

struct pg_state {
    int level;
    unsigned int current_prot;
    unsigned long start_address;
    unsigned long current_address;
    const struct addr_marker *marker;
};

static void print_prot(struct seq_file *m, unsigned int pr, int level)
{
    static const char * const level_name[] =
        { "ASCE", "PGD", "PUD", "PMD", "PTE" };

    seq_printf(m, "%s ", level_name[level]);
    if (pr & _PAGE_INVALID)
        seq_printf(m, "I\n");
    else
        seq_printf(m, "%s\n", pr & _PAGE_RO ? "RO" : "RW");
}

static void note_page(struct seq_file *m, struct pg_state *st,
             unsigned int new_prot, int level)
{
    static const char units[] = "KMGTPE";
    int width = sizeof(unsigned long) * 2;
    const char *unit = units;
    unsigned int prot, cur;
    unsigned long delta;

    /*
     * If we have a "break" in the series, we need to flush the state
     * that we have now. "break" is either changing perms, levels or
     * address space marker.
     */
    prot = new_prot;
    cur = st->current_prot;

    if (!st->level) {
        /* First entry */
        st->current_prot = new_prot;
        st->level = level;
        st->marker = address_markers;
        seq_printf(m, "---[ %s ]---\n", st->marker->name);
    } else if (prot != cur || level != st->level ||
           st->current_address >= st->marker[1].start_address) {
        /* Print the actual finished series */
        seq_printf(m, "0x%0*lx-0x%0*lx",
               width, st->start_address,
               width, st->current_address);
        delta = (st->current_address - st->start_address) >> 10;
        while (!(delta & 0x3ff) && unit[1]) {
            delta >>= 10;
            unit++;
        }
        seq_printf(m, "%9lu%c ", delta, *unit);
        print_prot(m, st->current_prot, st->level);
        if (st->current_address >= st->marker[1].start_address) {
            st->marker++;
            seq_printf(m, "---[ %s ]---\n", st->marker->name);
        }
        st->start_address = st->current_address;
        st->current_prot = new_prot;
        st->level = level;
    }
}

/*
 * The actual page table walker functions. In order to keep the implementation
 * of print_prot() short, we only check and pass _PAGE_INVALID and _PAGE_RO
 * flags to note_page() if a region, segment or page table entry is invalid or
 * read-only.
 * After all it's just a hint that the current level being walked contains an
 * invalid or read-only entry.
 */
static void walk_pte_level(struct seq_file *m, struct pg_state *st,
               pmd_t *pmd, unsigned long addr)
{
    unsigned int prot;
    pte_t *pte;
    int i;

    for (i = 0; i < PTRS_PER_PTE && addr < max_addr; i++) {
        st->current_address = addr;
        pte = pte_offset_kernel(pmd, addr);
        prot = pte_val(*pte) & (_PAGE_RO | _PAGE_INVALID);
        note_page(m, st, prot, 4);
        addr += PAGE_SIZE;
    }
}

static void walk_pmd_level(struct seq_file *m, struct pg_state *st,
               pud_t *pud, unsigned long addr)
{
    unsigned int prot;
    pmd_t *pmd;
    int i;

    for (i = 0; i < PTRS_PER_PMD && addr < max_addr; i++) {
        st->current_address = addr;
        pmd = pmd_offset(pud, addr);
        if (!pmd_none(*pmd)) {
            if (pmd_large(*pmd)) {
                prot = pmd_val(*pmd) & _SEGMENT_ENTRY_RO;
                note_page(m, st, prot, 3);
            } else
                walk_pte_level(m, st, pmd, addr);
        } else
            note_page(m, st, _PAGE_INVALID, 3);
        addr += PMD_SIZE;
    }
}

static void walk_pud_level(struct seq_file *m, struct pg_state *st,
               pgd_t *pgd, unsigned long addr)
{
    pud_t *pud;
    int i;

    for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) {
        st->current_address = addr;
        pud = pud_offset(pgd, addr);
        if (!pud_none(*pud))
            walk_pmd_level(m, st, pud, addr);
        else
            note_page(m, st, _PAGE_INVALID, 2);
        addr += PUD_SIZE;
    }
}

static void walk_pgd_level(struct seq_file *m)
{
    unsigned long addr = 0;
    struct pg_state st;
    pgd_t *pgd;
    int i;

    memset(&st, 0, sizeof(st));
    for (i = 0; i < PTRS_PER_PGD && addr < max_addr; i++) {
        st.current_address = addr;
        pgd = pgd_offset_k(addr);
        if (!pgd_none(*pgd))
            walk_pud_level(m, &st, pgd, addr);
        else
            note_page(m, &st, _PAGE_INVALID, 1);
        addr += PGDIR_SIZE;
    }
    /* Flush out the last page */
    st.current_address = max_addr;
    note_page(m, &st, 0, 0);
}

static int ptdump_show(struct seq_file *m, void *v)
{
    walk_pgd_level(m);
    return 0;
}

static int ptdump_open(struct inode *inode, struct file *filp)
{
    return single_open(filp, ptdump_show, NULL);
}

static const struct file_operations ptdump_fops = {
    .open       = ptdump_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static int pt_dump_init(void)
{
    /*
     * Figure out the maximum virtual address being accessible with the
     * kernel ASCE. We need this to keep the page table walker functions
     * from accessing non-existent entries.
     */
#ifdef CONFIG_32BIT
    max_addr = 1UL << 31;
#else
    max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2;
    max_addr = 1UL << (max_addr * 11 + 31);
    address_markers[MODULES_NR].start_address = MODULES_VADDR;
#endif
    address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
    address_markers[VMALLOC_NR].start_address = VMALLOC_START;
    debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
    return 0;
}
device_initcall(pt_dump_init);