root/arch/arm64/kvm/ptdump.c
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Debug helper used to dump the stage-2 pagetables of the system and their
 * associated permissions.
 *
 * Copyright (C) Google, 2024
 * Author: Sebastian Ene <sebastianene@google.com>
 */
#include <linux/debugfs.h>
#include <linux/kvm_host.h>
#include <linux/seq_file.h>

#include <asm/kvm_mmu.h>
#include <asm/kvm_pgtable.h>
#include <asm/ptdump.h>

#define MARKERS_LEN             2
#define KVM_PGTABLE_MAX_LEVELS  (KVM_PGTABLE_LAST_LEVEL + 1)

struct kvm_ptdump_guest_state {
        struct kvm              *kvm;
        struct ptdump_pg_state  parser_state;
        struct addr_marker      ipa_marker[MARKERS_LEN];
        struct ptdump_pg_level  level[KVM_PGTABLE_MAX_LEVELS];
        struct ptdump_range     range[MARKERS_LEN];
};

static const struct ptdump_prot_bits stage2_pte_bits[] = {
        {
                .mask   = PTE_VALID,
                .val    = PTE_VALID,
                .set    = " ",
                .clear  = "F",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
                .val    = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
                .set    = "R",
                .clear  = " ",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
                .val    = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
                .set    = "W",
                .clear  = " ",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_HI_S2_XN,
                .val    = 0b00UL << __bf_shf(KVM_PTE_LEAF_ATTR_HI_S2_XN),
                .set    = "px ux ",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_HI_S2_XN,
                .val    = 0b01UL << __bf_shf(KVM_PTE_LEAF_ATTR_HI_S2_XN),
                .set    = "PXNux ",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_HI_S2_XN,
                .val    = 0b10UL << __bf_shf(KVM_PTE_LEAF_ATTR_HI_S2_XN),
                .set    = "PXNUXN",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_HI_S2_XN,
                .val    = 0b11UL << __bf_shf(KVM_PTE_LEAF_ATTR_HI_S2_XN),
                .set    = "px UXN",
        },
        {
                .mask   = KVM_PTE_LEAF_ATTR_LO_S2_AF,
                .val    = KVM_PTE_LEAF_ATTR_LO_S2_AF,
                .set    = "AF",
                .clear  = "  ",
        },
        {
                .mask   = PMD_TYPE_MASK,
                .val    = PMD_TYPE_SECT,
                .set    = "BLK",
                .clear  = "   ",
        },
};

static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx,
                              enum kvm_pgtable_walk_flags visit)
{
        struct ptdump_pg_state *st = ctx->arg;
        struct ptdump_state *pt_st = &st->ptdump;

        note_page(pt_st, ctx->addr, ctx->level, ctx->old);

        return 0;
}

static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl)
{
        u32 i;
        u64 mask;

        if (WARN_ON_ONCE(start_lvl >= KVM_PGTABLE_LAST_LEVEL))
                return -EINVAL;

        mask = 0;
        for (i = 0; i < ARRAY_SIZE(stage2_pte_bits); i++)
                mask |= stage2_pte_bits[i].mask;

        for (i = start_lvl; i < KVM_PGTABLE_MAX_LEVELS; i++) {
                snprintf(level[i].name, sizeof(level[i].name), "%u", i);

                level[i].num    = ARRAY_SIZE(stage2_pte_bits);
                level[i].bits   = stage2_pte_bits;
                level[i].mask   = mask;
        }

        return 0;
}

static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm *kvm)
{
        struct kvm_ptdump_guest_state *st;
        struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
        struct kvm_pgtable *pgtable = mmu->pgt;
        int ret;

        st = kzalloc_obj(struct kvm_ptdump_guest_state, GFP_KERNEL_ACCOUNT);
        if (!st)
                return ERR_PTR(-ENOMEM);

        ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level);
        if (ret) {
                kfree(st);
                return ERR_PTR(ret);
        }

        st->ipa_marker[0].name          = "Guest IPA";
        st->ipa_marker[1].start_address = BIT(pgtable->ia_bits);
        st->range[0].end                = BIT(pgtable->ia_bits);

        st->kvm                         = kvm;
        st->parser_state = (struct ptdump_pg_state) {
                .marker         = &st->ipa_marker[0],
                .level          = -1,
                .pg_level       = &st->level[0],
                .ptdump.range   = &st->range[0],
                .start_address  = 0,
        };

        return st;
}

static int kvm_ptdump_guest_show(struct seq_file *m, void *unused)
{
        int ret;
        struct kvm_ptdump_guest_state *st = m->private;
        struct kvm *kvm = st->kvm;
        struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
        struct ptdump_pg_state *parser_state = &st->parser_state;
        struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) {
                .cb     = kvm_ptdump_visitor,
                .arg    = parser_state,
                .flags  = KVM_PGTABLE_WALK_LEAF,
        };

        parser_state->seq = m;

        write_lock(&kvm->mmu_lock);
        ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker);
        write_unlock(&kvm->mmu_lock);

        return ret;
}

static int kvm_ptdump_guest_open(struct inode *m, struct file *file)
{
        struct kvm *kvm = m->i_private;
        struct kvm_ptdump_guest_state *st;
        int ret;

        if (!kvm_get_kvm_safe(kvm))
                return -ENOENT;

        st = kvm_ptdump_parser_create(kvm);
        if (IS_ERR(st)) {
                ret = PTR_ERR(st);
                goto err_with_kvm_ref;
        }

        ret = single_open(file, kvm_ptdump_guest_show, st);
        if (!ret)
                return 0;

        kfree(st);
err_with_kvm_ref:
        kvm_put_kvm(kvm);
        return ret;
}

static int kvm_ptdump_guest_close(struct inode *m, struct file *file)
{
        struct kvm *kvm = m->i_private;
        void *st = ((struct seq_file *)file->private_data)->private;

        kfree(st);
        kvm_put_kvm(kvm);

        return single_release(m, file);
}

static const struct file_operations kvm_ptdump_guest_fops = {
        .open           = kvm_ptdump_guest_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = kvm_ptdump_guest_close,
};

static int kvm_pgtable_range_show(struct seq_file *m, void *unused)
{
        struct kvm_pgtable *pgtable = m->private;

        seq_printf(m, "%2u\n", pgtable->ia_bits);
        return 0;
}

static int kvm_pgtable_levels_show(struct seq_file *m, void *unused)
{
        struct kvm_pgtable *pgtable = m->private;

        seq_printf(m, "%1d\n", KVM_PGTABLE_MAX_LEVELS - pgtable->start_level);
        return 0;
}

static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file,
                                    int (*show)(struct seq_file *, void *))
{
        struct kvm *kvm = m->i_private;
        struct kvm_pgtable *pgtable;
        int ret;

        if (!kvm_get_kvm_safe(kvm))
                return -ENOENT;

        pgtable = kvm->arch.mmu.pgt;

        ret = single_open(file, show, pgtable);
        if (ret < 0)
                kvm_put_kvm(kvm);
        return ret;
}

static int kvm_pgtable_range_open(struct inode *m, struct file *file)
{
        return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_range_show);
}

static int kvm_pgtable_levels_open(struct inode *m, struct file *file)
{
        return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_levels_show);
}

static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file)
{
        struct kvm *kvm = m->i_private;

        kvm_put_kvm(kvm);
        return single_release(m, file);
}

static const struct file_operations kvm_pgtable_range_fops = {
        .open           = kvm_pgtable_range_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = kvm_pgtable_debugfs_close,
};

static const struct file_operations kvm_pgtable_levels_fops = {
        .open           = kvm_pgtable_levels_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = kvm_pgtable_debugfs_close,
};

void kvm_s2_ptdump_create_debugfs(struct kvm *kvm)
{
        debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry,
                            kvm, &kvm_ptdump_guest_fops);
        debugfs_create_file("ipa_range", 0400, kvm->debugfs_dentry, kvm,
                            &kvm_pgtable_range_fops);
        debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry,
                            kvm, &kvm_pgtable_levels_fops);
}