ARM: add support to dump the kernel page tables
Laura Abbott
lauraa at codeaurora.org
Thu Oct 31 13:28:38 EDT 2013
On 10/24/2013 12:16 AM, Russell King - ARM Linux wrote:
...
> +
> +static const struct prot_bits pte_bits[] = {
> + {
> + .mask = L_PTE_USER,
> + .val = L_PTE_USER,
> + .set = "USR",
> + .clear = " ",
> + }, {
> + .mask = L_PTE_RDONLY,
> + .val = L_PTE_RDONLY,
> + .set = "ro",
> + .clear = "RW",
> + }, {
> + .mask = L_PTE_XN,
> + .val = L_PTE_XN,
> + .set = "NX",
> + .clear = "x ",
> + }, {
> + .mask = L_PTE_SHARED,
> + .val = L_PTE_SHARED,
> + .set = "SHD",
> + .clear = " ",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_UNCACHED,
> + .set = "SO/UNCACHED",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_BUFFERABLE,
> + .set = "MEM/BUFFERABLE/WC",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_WRITETHROUGH,
> + .set = "MEM/CACHED/WT",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_WRITEBACK,
> + .set = "MEM/CACHED/WBRA",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_MINICACHE,
> + .set = "MEM/MINICACHE",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_WRITEALLOC,
> + .set = "MEM/CACHED/WBWA",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_DEV_SHARED,
> + .set = "DEV/SHARED",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_DEV_NONSHARED,
> + .set = "DEV/NONSHARED",
> + }, {
L_PTE_MT_DEV_SHARED and L_PTE_MT_DEV_NONSHARED are the same on LPAE
systems which leads to bad output:
0xcd400000-0xcd401000 4K RW NX SHD DEV/SHARED DEV/NONSHARED
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_DEV_WC,
> + .set = "DEV/WC",
> + }, {
> + .mask = L_PTE_MT_MASK,
> + .val = L_PTE_MT_DEV_CACHED,
> + .set = "DEV/CACHED",
> + },
> +};
> +
> +static const struct prot_bits section_bits[] = {
> + /* These are approximate */
> + {
> + .mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
> + .val = 0,
> + .set = " ro",
> + }, {
> + .mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
> + .val = PMD_SECT_AP_WRITE,
> + .set = " RW",
> + }, {
> + .mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
> + .val = PMD_SECT_AP_READ,
> + .set = "USR RO",
> + }, {
> + .mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
> + .val = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
> + .set = "USR RW",
> + }, {
Same issue here for PMD_SECT_AP_READ and PMD_SEC_AP_WRITE, both of those
are 0 on LPAE so the output looks strange:
0xc0000000-0xcd400000 212M ro RW USR RO USR RW x SHD
> + .mask = PMD_SECT_XN,
> + .val = PMD_SECT_XN,
> + .set = "NX",
> + .clear = "x ",
> + }, {
> + .mask = PMD_SECT_S,
> + .val = PMD_SECT_S,
> + .set = "SHD",
> + .clear = " ",
> + },
> +};
> +
> +struct pg_level {
> + const struct prot_bits *bits;
> + size_t num;
> + u64 mask;
> +};
> +
> +static struct pg_level pg_level[] = {
> + {
> + }, { /* pgd */
> + }, { /* pud */
> + }, { /* pmd */
> + .bits = section_bits,
> + .num = ARRAY_SIZE(section_bits),
> + }, { /* pte */
> + .bits = pte_bits,
> + .num = ARRAY_SIZE(pte_bits),
> + },
> +};
> +
> +static void dump_prot(struct pg_state *st, const struct prot_bits *bits, size_t num)
> +{
> + unsigned i;
> +
> + for (i = 0; i < num; i++, bits++) {
> + const char *s;
> +
> + if ((st->current_prot & bits->mask) == bits->val)
> + s = bits->set;
> + else
> + s = bits->clear;
> +
> + if (s)
> + seq_printf(st->seq, " %s", s);
> + }
> +}
> +
> +static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u64 val)
> +{
> + static const char units[] = "KMGTPE";
> + u64 prot = val & pg_level[level].mask;
> +
> + if (addr < USER_PGTABLES_CEILING)
> + return;
> +
> + if (!st->level) {
> + st->level = level;
> + st->current_prot = prot;
> + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + } else if (prot != st->current_prot || level != st->level ||
> + addr >= st->marker[1].start_address) {
> + const char *unit = units;
> + unsigned long delta;
> +
> + if (st->current_prot) {
> + seq_printf(st->seq, "0x%08lx-0x%08lx ",
> + st->start_address, addr);
> +
> + delta = (addr - st->start_address) >> 10;
> + while (!(delta & 1023) && unit[1]) {
> + delta >>= 10;
> + unit++;
> + }
> + seq_printf(st->seq, "%9lu%c", delta, *unit);
> + if (pg_level[st->level].bits)
> + dump_prot(st, pg_level[st->level].bits, pg_level[st->level].num);
> + seq_printf(st->seq, "\n");
> + }
> +
> + if (addr >= st->marker[1].start_address) {
> + st->marker++;
> + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + }
> + st->start_address = addr;
> + st->current_prot = prot;
> + st->level = level;
> + }
> +}
> +
> +static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
> +{
> + pte_t *pte = pte_offset_kernel(pmd, 0);
> + unsigned long addr;
> + unsigned i;
> +
> + for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
> + addr = start + i * PAGE_SIZE;
> + note_page(st, addr, 4, pte_val(*pte));
> + }
> +}
> +
> +static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
> +{
> + pmd_t *pmd = pmd_offset(pud, 0);
> + unsigned long addr;
> + unsigned i;
> +
> + for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
> + addr = start + i * PMD_SIZE;
> + if (pmd_none(*pmd) || pmd_large(*pmd) || !pmd_present(*pmd))
> + note_page(st, addr, 3, pmd_val(*pmd));
> + else
> + walk_pte(st, pmd, addr);
> + }
> +}
> +
> +static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
> +{
> + pud_t *pud = pud_offset(pgd, 0);
> + unsigned long addr;
> + unsigned i;
> +
> + for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
> + addr = start + i * PUD_SIZE;
> + if (!pud_none(*pud)) {
> + walk_pmd(st, pud, addr);
> + } else {
> + note_page(st, addr, 2, pud_val(*pud));
> + }
> + }
> +}
> +
> +static void walk_pgd(struct seq_file *m)
> +{
> + pgd_t *pgd = swapper_pg_dir;
> + struct pg_state st;
> + unsigned long addr;
> + unsigned i;
> +
> + memset(&st, 0, sizeof(st));
> + st.seq = m;
> + st.marker = address_markers;
> +
> + for (i = USER_PGTABLES_CEILING / PGDIR_SIZE;
> + i < PTRS_PER_PGD; i++, pgd++) {
> + addr = i * PGDIR_SIZE;
> + if (!pgd_none(*pgd)) {
> + walk_pud(&st, pgd, addr);
> + } else {
> + note_page(&st, addr, 1, pgd_val(*pgd));
> + }
> + }
> +
> + note_page(&st, 0, 0, 0);
> +}
> +
> +static int ptdump_show(struct seq_file *m, void *v)
> +{
> + walk_pgd(m);
> + return 0;
> +}
> +
> +static int ptdump_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, ptdump_show, NULL);
> +}
> +
> +static const struct file_operations ptdump_fops = {
> + .open = ptdump_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +static int ptdump_init(void)
> +{
> + struct dentry *pe;
> + unsigned i, j;
> +
> + for (i = 0; i < ARRAY_SIZE(pg_level); i++)
> + if (pg_level[i].bits)
> + for (j = 0; j < pg_level[i].num; j++)
> + pg_level[i].mask |= pg_level[i].bits[j].mask;
> +
> + address_markers[2].start_address = VMALLOC_START;
> +
> + pe = debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
> + &ptdump_fops);
> + return pe ? 0 : -ENOMEM;
> +}
> +__initcall(ptdump_init);
>
Thanks,
Laura
--
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