On 22/03/16 09:04, Rashmica Gupta wrote:
> Useful to be able to dump the kernels page tables to check permissions
> and memory types - derived from arm64's implementation.
>
> Add a debugfs file to check the page tables. To use this the PPC_PTDUMP
> config option must be selected.
>
> Signed-off-by: Rashmica Gupta <rashm...@gmail.com>
> ---
> arch/powerpc/Kconfig.debug | 12 ++
> arch/powerpc/mm/Makefile | 1 +
> arch/powerpc/mm/dump_linuxpagetables.c | 377
> +++++++++++++++++++++++++++++++++
> 3 files changed, 390 insertions(+)
> create mode 100644 arch/powerpc/mm/dump_linuxpagetables.c
>
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index 638f9ce740f5..26a60effea1a 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -344,4 +344,16 @@ config FAIL_IOMMU
>
> If you are unsure, say N.
>
> +config PPC_PTDUMP
> + bool "Export kernel pagetable layout to userspace via debugfs"
> + depends on DEBUG_KERNEL
> + select DEBUG_FS
> + help
> + This option exports the state of the kernel pagetables to a
> + debugfs file. This is only useful for kernel developers who are
> + working in architecture specific areas of the kernel - probably
> + not a good idea to enable this feature in a production kernel.
> +
> + If you are unsure, say N.
> +
Some minor comments below, but otherwise
Acked-by: Balbir Singh <bsinghar...@gmail.com>
> endmenu
> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
> index adfee3f1aeb9..6935c6204fbc 100644
> --- a/arch/powerpc/mm/Makefile
> +++ b/arch/powerpc/mm/Makefile
> @@ -41,3 +41,4 @@ obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
> obj-$(CONFIG_HIGHMEM) += highmem.o
> obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o
> obj-$(CONFIG_SPAPR_TCE_IOMMU) += mmu_context_iommu.o
> +obj-$(CONFIG_PPC_PTDUMP) += dump_linuxpagetables.o
> diff --git a/arch/powerpc/mm/dump_linuxpagetables.c
> b/arch/powerpc/mm/dump_linuxpagetables.c
> new file mode 100644
> index 000000000000..f97fbfdac4b9
> --- /dev/null
> +++ b/arch/powerpc/mm/dump_linuxpagetables.c
> @@ -0,0 +1,377 @@
> +/*
> + * Copyright 2016, Rashmica Gupta, IBM Corp.
> + *
> + * This traverses the kernel pagetables and dumps the
> + * information about the used sections of memory to
> + * /sys/kernel/debug/kernel_pagetables.
> + *
> + * Derived from the arm64 implementation:
> + * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
> + * (C) Copyright 2008 Intel Corporation, Arjan van de Ven.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; version 2
> + * of the License.
> + */
> +#include <linux/debugfs.h>
> +#include <linux/fs.h>
> +#include <linux/io.h>
> +#include <linux/mm.h>
> +#include <linux/sched.h>
> +#include <linux/seq_file.h>
> +#include <asm/fixmap.h>
> +#include <asm/pgtable.h>
> +#include <linux/const.h>
> +#include <asm/page.h>
> +#include <asm/pgalloc.h>
> +
> +struct addr_marker {
> + unsigned long start_address;
> + const char *name;
> +};
> +
> +static struct addr_marker address_markers[] = {
> + { VMALLOC_START, "vmalloc() Area" },
> + { VMALLOC_END, "vmalloc() End" },
> + { ISA_IO_BASE, "isa I/O start" },
> + { ISA_IO_END, "isa I/O end" },
> + { PHB_IO_BASE, "phb I/O start" },
> + { PHB_IO_END, "phb I/O end" },
> + { IOREMAP_BASE, "I/O remap start" },
> + { IOREMAP_END, "I/O remap end" },
> + { -1, NULL },
> +};
> +
> +/*
> + * To visualise what is happening,
> + *
> + * - PTRS_PER_P** = how many entries there are in the corresponding P**
> + * - P**_SHIFT = how many bits of the address we use to index into the
> + * corresponding P**
> + * - P**_SIZE is how much memory we can access through the table - not the
> + * size of the table itself.
> + * P**={PGD, PUD, PMD, PTE}
> + *
> + *
> + * Each entry of the PGD points to a PUD. Each entry of a PUD points to a
> + * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to
> + * a page.
> + *
> + * In the case where there are only 3 levels, the PUD is folded into the
> + * PGD: every PUD has only one entry which points to the PMD.
> + *
> + * The page dumper groups page table entries of the same type into a single
> + * description. It uses pg_state to track the range information while
> + * iterating over the PTE entries. When the continuity is broken it then
> + * dumps out a description of the range - ie PTEs that are virtually
> contiguous
> + * with the same PTE flags are chunked together. This is to make it clear how
> + * different areas of the kernel virtual memory are used.
> + *
> + */
> +struct pg_state {
> + struct seq_file *seq;
> + const struct addr_marker *marker;
> + unsigned long start_address;
> + unsigned level;
> + u64 current_flags;
> +};
> +
> +struct flag_info {
> + u64 mask;
> + u64 val;
> + const char *set;
> + const char *clear;
> +};
> +
> +static const struct flag_info flag_array[] = {
> + {
> + .mask = _PAGE_USER,
> + .val = _PAGE_USER,
> + .set = "user",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_RW,
> + .val = _PAGE_RW,
> + .set = "rw",
> + .clear = "ro",
> + }, {
> + .mask = _PAGE_EXEC,
> + .val = _PAGE_EXEC,
> + .set = " X ",
Can we make this small "x" to sort of go in line with "rw"/"ro"
> + .clear = " ",
> + }, {
> + .mask = _PAGE_PTE,
> + .val = _PAGE_PTE,
> + .set = "pte",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_PRESENT,
> + .val = _PAGE_PRESENT,
> + .set = "present",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_HASHPTE,
> + .val = _PAGE_HASHPTE,
> + .set = "hpte",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_GUARDED,
> + .val = _PAGE_GUARDED,
> + .set = "guarded",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_DIRTY,
> + .val = _PAGE_DIRTY,
> + .set = "dirty",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_ACCESSED,
> + .val = _PAGE_ACCESSED,
> + .set = "accessed",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_WRITETHRU,
> + .val = _PAGE_WRITETHRU,
> + .set = "write through",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_NO_CACHE,
> + .val = _PAGE_NO_CACHE,
> + .set = "no cache",
> + .clear = " ",
> + }, {
> + .mask = _PAGE_BUSY,
> + .val = _PAGE_BUSY,
> + .set = "busy",
> + }, {
> + .mask = _PAGE_COMBO,
> + .val = _PAGE_COMBO,
> + .set = "combo",
> + }, {
> + .mask = _PAGE_F_GIX,
> + .val = _PAGE_F_GIX,
> + .set = "f_gix",
Can we use "primary"?
> + }, {
> + .mask = _PAGE_F_SECOND,
> + .val = _PAGE_F_SECOND,
> + .set = "f_second",
"secondary idx"
> + }, {
> + .mask = _PAGE_SPECIAL,
> + .val = _PAGE_SPECIAL,
> + .set = "special",
> + }, {
> + .mask = _PAGE_4K_PFN,
> + .val = _PAGE_4K_PFN,
> + .set = "4K_pfn"
> + }
> +};
> +
> +struct pgtable_level {
> + const struct flag_info *flag;
> + size_t num;
> + u64 mask;
> +};
> +
> +static struct pgtable_level pg_level[] = {
> + {
> + }, { /* pgd */
> + .flag = flag_array,
> + .num = ARRAY_SIZE(flag_array),
> + }, { /* pud */
> + .flag = flag_array,
> + .num = ARRAY_SIZE(flag_array),
> + }, { /* pmd */
> + .flag = flag_array,
> + .num = ARRAY_SIZE(flag_array),
> + }, { /* pte */
> + .flag = flag_array,
> + .num = ARRAY_SIZE(flag_array),
> + },
> +};
> +
> +static void dump_flag(struct pg_state *st, const struct flag_info *flag,
> + size_t num)
> +{
> + unsigned i;
> +
> + for (i = 0; i < num; i++, flag++) {
> + const char *s;
> +
> + if ((st->current_flags & flag->mask) == flag->val)
> + s = flag->set;
> + else
> + s = flag->clear;
> +
> + if (s)
> + seq_printf(st->seq, " %s", s);
> + }
> +}
> +
> +static void dump_addr(struct pg_state *st, unsigned long addr)
> +{
> + static const char units[] = "KMGTPE";
> + const char *unit = units;
> + unsigned long delta;
> +
> + seq_printf(st->seq, "0x%016lx-0x%016lx ", st->start_address, addr-1);
> + delta = (addr - st->start_address) >> 10;
> + /* Work out what appropriate unit to use */
> + while (!(delta & 1023) && unit[1]) {
1023, I think ((1 << 10) - 1) is easier to understand but again you may find a
better way of encapsulating this
> + delta >>= 10;
> + unit++;
> + }
> + seq_printf(st->seq, "%9lu%c", delta, *unit);
> +
> +}
> +
> +static void note_page(struct pg_state *st, unsigned long addr, unsigned
> level,
> + u64 val)
> +{
> + u64 flag = val & pg_level[level].mask;
> +
> + /* At first no level is set */
> + if (!st->level) {
> + st->level = level;
> + st->current_flags = flag;
> + st->start_address = addr;
> + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + /*
> + * Dump the section of virtual memory when:
> + * - the PTE flags from one entry to the next differs.
> + * - we change levels in the tree.
> + * - the address is in a different section of memory and is thus
> + * used for a different purpose, regardless of the flags.
> + */
> + } else if (flag != st->current_flags || level != st->level ||
> + addr >= st->marker[1].start_address) {
> +
> + /* Check the PTE flags */
> + if (st->current_flags) {
> + dump_addr(st, addr);
> +
> + /* Dump all the flags */
> + if (pg_level[st->level].flag)
> + dump_flag(st, pg_level[st->level].flag,
> + pg_level[st->level].num);
> + seq_puts(st->seq, "\n");
> + }
> +
> + /* Address indicates we have passed the end of the
> + * current section of virtual memory
> + */
> + while (addr >= st->marker[1].start_address) {
> + st->marker++;
> + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
> + }
> + st->start_address = addr;
> + st->current_flags = flag;
> + 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 exists */
> + walk_pte(st, pmd, addr);
> + else
> + note_page(st, addr, 3, pmd_val(*pmd));
> + }
> +}
> +
> +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))
> + /* pud exists */
> + walk_pmd(st, pud, addr);
> + else
> + note_page(st, addr, 2, pud_val(*pud));
> + }
> +}
> +
> +static void walk_pgd(struct pg_state *st, unsigned long start)
> +{
> + pgd_t *pgd = pgd_offset_k(0UL);
> + unsigned i;
> + unsigned long addr;
> +
> + for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
> + addr = start + i * PGDIR_SIZE;
> + if (!pgd_none(*pgd))
> + /* pgd exists */
> + walk_pud(st, pgd, addr);
> + else
> + note_page(st, addr, 1, pgd_val(*pgd));
> + }
> +}
> +
> +static int ptdump_show(struct seq_file *m, void *v)
> +{
> + struct pg_state st = {
> + .seq = m,
> + .start_address = KERN_VIRT_START,
> + .marker = address_markers,
> + };
> + /* Traverse kernel page tables */
> + walk_pgd(&st, KERN_VIRT_START);
> + note_page(&st, 0, 0, 0);
> + 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 void build_pgtable_complete_mask(void)
> +{
> + unsigned i, j;
> +
> + for (i = 0; i < ARRAY_SIZE(pg_level); i++)
> + if (pg_level[i].flag)
> + for (j = 0; j < pg_level[i].num; j++)
> + pg_level[i].mask |= pg_level[i].flag[j].mask;
> +}
> +
> +static int ptdump_init(void)
> +{
> + struct dentry *debugfs_file;
> +
> + build_pgtable_complete_mask();
> + debugfs_file = debugfs_create_file("kernel_pagetables", 0400, NULL,
> + NULL, &ptdump_fops);
> + return debugfs_file ? 0 : -ENOMEM;
> +}
> +device_initcall(ptdump_init);
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