// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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.
 */
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/hugetlb.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/ptdump.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <asm/fixmap.h>
#include <linux/const.h>
#include <linux/kasan.h>
#include <asm/page.h>
#include <asm/hugetlb.h>

#include <mm/mmu_decl.h>

#include "ptdump.h"

/*
 * 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 ptdump_state ptdump;
        struct seq_file *seq;
        const struct addr_marker *marker;
        unsigned long start_address;
        unsigned long start_pa;
        int level;
        u64 current_flags;
        bool check_wx;
        unsigned long wx_pages;
};

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

static struct addr_marker address_markers[] = {
        { 0,    "Start of kernel VM" },
#ifdef MODULES_VADDR
        { 0,    "modules start" },
        { 0,    "modules end" },
#endif
        { 0,    "vmalloc() Area" },
        { 0,    "vmalloc() End" },
#ifdef CONFIG_PPC64
        { 0,    "isa I/O start" },
        { 0,    "isa I/O end" },
        { 0,    "phb I/O start" },
        { 0,    "phb I/O end" },
        { 0,    "I/O remap start" },
        { 0,    "I/O remap end" },
        { 0,    "vmemmap start" },
#else
        { 0,    "Early I/O remap start" },
        { 0,    "Early I/O remap end" },
#ifdef CONFIG_HIGHMEM
        { 0,    "Highmem PTEs start" },
        { 0,    "Highmem PTEs end" },
#endif
        { 0,    "Fixmap start" },
        { 0,    "Fixmap end" },
#endif
#ifdef CONFIG_KASAN
        { 0,    "kasan shadow mem start" },
        { 0,    "kasan shadow mem end" },
#endif
        { -1,   NULL },
};

static struct ptdump_range ptdump_range[] __ro_after_init = {
        {TASK_SIZE_MAX, ~0UL},
        {0, 0}
};

#define pt_dump_seq_printf(m, fmt, args...)     \
({                                              \
        if (m)                                  \
                seq_printf(m, fmt, ##args);     \
})

#define pt_dump_seq_putc(m, c)          \
({                                      \
        if (m)                          \
                seq_putc(m, c);         \
})

void pt_dump_size(struct seq_file *m, unsigned long size)
{
        static const char units[] = " KMGTPE";
        const char *unit = units;

        /* Work out what appropriate unit to use */
        while (!(size & 1023) && unit[1]) {
                size >>= 10;
                unit++;
        }
        pt_dump_seq_printf(m, "%9lu%c ", size, *unit);
}

static void dump_flag_info(struct pg_state *st, const struct flag_info
                *flag, u64 pte, int num)
{
        unsigned int i;

        for (i = 0; i < num; i++, flag++) {
                const char *s = NULL;
                u64 val;

                /* flag not defined so don't check it */
                if (flag->mask == 0)
                        continue;
                /* Some 'flags' are actually values */
                if (flag->is_val) {
                        val = pte & flag->val;
                        if (flag->shift)
                                val = val >> flag->shift;
                        pt_dump_seq_printf(st->seq, "  %s:%llx", flag->set, val);
                } else {
                        if ((pte & flag->mask) == flag->val)
                                s = flag->set;
                        else
                                s = flag->clear;
                        if (s)
                                pt_dump_seq_printf(st->seq, "  %s", s);
                }
                st->current_flags &= ~flag->mask;
        }
        if (st->current_flags != 0)
                pt_dump_seq_printf(st->seq, "  unknown flags:%llx", st->current_flags);
}

static void dump_addr(struct pg_state *st, unsigned long addr)
{
#ifdef CONFIG_PPC64
#define REG             "0x%016lx"
#else
#define REG             "0x%08lx"
#endif

        pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
        pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
        pt_dump_size(st->seq, addr - st->start_address);
        pt_dump_seq_printf(st->seq, "%s ", pg_level[st->level].name);
}

static void note_prot_wx(struct pg_state *st, unsigned long addr)
{
        pte_t pte = __pte(st->current_flags);

        if (!st->check_wx)
                return;

        if (!pte_write(pte) || !pte_exec(pte))
                return;

        WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
                  "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
                  (void *)st->start_address, (void *)st->start_address);

        st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
}

static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val)
{
        u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
        u64 pa = val & PTE_RPN_MASK;

        st->level = level;
        st->current_flags = flag;
        st->start_address = addr;
        st->start_pa = pa;

        while (addr >= st->marker[1].start_address) {
                st->marker++;
                pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
        }
}

static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
{
        u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
        struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);

        /* At first no level is set */
        if (st->level == -1) {
                pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
                note_page_update_state(st, addr, level, val);
        /*
         * 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) {
                        note_prot_wx(st, addr);
                        dump_addr(st, addr);

                        /* Dump all the flags */
                        if (pg_level[st->level].flag)
                                dump_flag_info(st, pg_level[st->level].flag,
                                          st->current_flags,
                                          pg_level[st->level].num);

                        pt_dump_seq_putc(st->seq, '\n');
                }

                /*
                 * Address indicates we have passed the end of the
                 * current section of virtual memory
                 */
                note_page_update_state(st, addr, level, val);
        }
}

static void populate_markers(void)
{
        int i = 0;

#ifdef CONFIG_PPC64
        address_markers[i++].start_address = PAGE_OFFSET;
#else
        address_markers[i++].start_address = TASK_SIZE;
#endif
#ifdef MODULES_VADDR
        address_markers[i++].start_address = MODULES_VADDR;
        address_markers[i++].start_address = MODULES_END;
#endif
        address_markers[i++].start_address = VMALLOC_START;
        address_markers[i++].start_address = VMALLOC_END;
#ifdef CONFIG_PPC64
        address_markers[i++].start_address = ISA_IO_BASE;
        address_markers[i++].start_address = ISA_IO_END;
        address_markers[i++].start_address = PHB_IO_BASE;
        address_markers[i++].start_address = PHB_IO_END;
        address_markers[i++].start_address = IOREMAP_BASE;
        address_markers[i++].start_address = IOREMAP_END;
        /* What is the ifdef about? */
#ifdef CONFIG_PPC_BOOK3S_64
        address_markers[i++].start_address =  H_VMEMMAP_START;
#else
        address_markers[i++].start_address =  VMEMMAP_BASE;
#endif
#else /* !CONFIG_PPC64 */
        address_markers[i++].start_address = ioremap_bot;
        address_markers[i++].start_address = IOREMAP_TOP;
#ifdef CONFIG_HIGHMEM
        address_markers[i++].start_address = PKMAP_BASE;
        address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
#endif
        address_markers[i++].start_address = FIXADDR_START;
        address_markers[i++].start_address = FIXADDR_TOP;
#endif /* CONFIG_PPC64 */
#ifdef CONFIG_KASAN
        address_markers[i++].start_address = KASAN_SHADOW_START;
        address_markers[i++].start_address = KASAN_SHADOW_END;
#endif
}

static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
{
        note_page(pt_st, addr, 4, pte_val(pte));
}

static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
{
        note_page(pt_st, addr, 3, pmd_val(pmd));
}

static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
{
        note_page(pt_st, addr, 2, pud_val(pud));
}

static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
{
        note_page(pt_st, addr, 1, p4d_val(p4d));
}

static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
{
        note_page(pt_st, addr, 0, pgd_val(pgd));
}

static void note_page_flush(struct ptdump_state *pt_st)
{
        pte_t pte_zero = {0};

        note_page(pt_st, 0, -1, pte_val(pte_zero));
}

static int ptdump_show(struct seq_file *m, void *v)
{
        struct pg_state st = {
                .seq = m,
                .marker = address_markers,
                .level = -1,
                .ptdump = {
                        .note_page_pte = note_page_pte,
                        .note_page_pmd = note_page_pmd,
                        .note_page_pud = note_page_pud,
                        .note_page_p4d = note_page_p4d,
                        .note_page_pgd = note_page_pgd,
                        .note_page_flush = note_page_flush,
                        .range = ptdump_range,
                }
        };

        /* Traverse kernel page tables */
        ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
        return 0;
}

DEFINE_SHOW_ATTRIBUTE(ptdump);

static void __init build_pgtable_complete_mask(void)
{
        unsigned int 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;
}

bool ptdump_check_wx(void)
{
        struct pg_state st = {
                .seq = NULL,
                .marker = (struct addr_marker[]) {
                        { 0, NULL},
                        { -1, NULL},
                },
                .level = -1,
                .check_wx = true,
                .ptdump = {
                        .note_page_pte = note_page_pte,
                        .note_page_pmd = note_page_pmd,
                        .note_page_pud = note_page_pud,
                        .note_page_p4d = note_page_p4d,
                        .note_page_pgd = note_page_pgd,
                        .note_page_flush = note_page_flush,
                        .range = ptdump_range,
                }
        };

        if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO))
                return true;

        ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);

        if (st.wx_pages) {
                pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
                        st.wx_pages);

                return false;
        } else {
                pr_info("Checked W+X mappings: passed, no W+X pages found\n");

                return true;
        }
}

static int __init ptdump_init(void)
{
#ifdef CONFIG_PPC64
        if (!radix_enabled())
                ptdump_range[0].start = KERN_VIRT_START;
        else
                ptdump_range[0].start = PAGE_OFFSET;

        ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD);
#endif

        populate_markers();
        build_pgtable_complete_mask();

        if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS))
                debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);

        return 0;
}
device_initcall(ptdump_init);