// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2026 Christian Brauner <brauner@kernel.org> */

/*
 * BPF LSM block device integrity tracker for dm-verity.
 *
 * Tracks block devices in a hashmap keyed by bd_dev.  When dm-verity
 * calls security_bdev_setintegrity() during verity_preresume(), the
 * setintegrity hook records the roothash and signature-validity data.
 * The free hook cleans up when the device goes away.  The alloc hook
 * counts allocations for test validation.
 *
 * The sleepable hooks exercise bpf_copy_from_user() to verify that
 * the sleepable classification actually permits sleepable helpers.
 */

#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

struct verity_info {
        __u8  has_roothash;     /* LSM_INT_DMVERITY_ROOTHASH seen */
        __u8  sig_valid;        /* LSM_INT_DMVERITY_SIG_VALID value (non-NULL = valid) */
        __u32 setintegrity_cnt; /* total setintegrity calls for this dev */
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(max_entries, 64);
        __type(key, __u32);             /* dev_t from bdev->bd_dev */
        __type(value, struct verity_info);
} verity_devices SEC(".maps");

/* Global counters exposed to userspace via skeleton bss. */
int alloc_count;

char _license[] SEC("license") = "GPL";

SEC("lsm.s/bdev_setintegrity")
int BPF_PROG(bdev_setintegrity, struct block_device *bdev,
             enum lsm_integrity_type type, const void *value, size_t size)
{
        struct verity_info zero = {};
        struct verity_info *info;
        __u32 dev;
        char buf;

        /*
         * Exercise a sleepable helper to confirm the verifier
         * allows it in this sleepable hook.
         */
        (void)bpf_copy_from_user(&buf, sizeof(buf), NULL);

        dev = bdev->bd_dev;

        info = bpf_map_lookup_elem(&verity_devices, &dev);
        if (!info) {
                bpf_map_update_elem(&verity_devices, &dev, &zero, BPF_NOEXIST);
                info = bpf_map_lookup_elem(&verity_devices, &dev);
                if (!info)
                        return 0;
        }

        if (type == LSM_INT_DMVERITY_ROOTHASH)
                info->has_roothash = 1;
        else if (type == LSM_INT_DMVERITY_SIG_VALID)
                info->sig_valid = (value != NULL);

        __sync_fetch_and_add(&info->setintegrity_cnt, 1);

        return 0;
}

SEC("lsm/bdev_free_security")
void BPF_PROG(bdev_free_security, struct block_device *bdev)
{
        __u32 dev = bdev->bd_dev;

        bpf_map_delete_elem(&verity_devices, &dev);
}

SEC("lsm.s/bdev_alloc_security")
int BPF_PROG(bdev_alloc_security, struct block_device *bdev)
{
        char buf;

        /*
         * Exercise a sleepable helper to confirm the verifier
         * allows it in this sleepable hook.
         */
        (void)bpf_copy_from_user(&buf, sizeof(buf), NULL);

        __sync_fetch_and_add(&alloc_count, 1);

        return 0;
}