nanowasm/src/section/code.c

/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2024  Xavier Del Campo Romero
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#include <log.h>
#include <nanowasm/nw.h>
#include <opcodes.h>
#include <interp.h>
#include <sections.h>
#include <wasm_types.h>
#include <errno.h>
#include <inttypes.h>
#include <stdint.h>
#include <string.h>

static int check_body(FILE *const f, const unsigned long n)
{
    unsigned long rem = n;

    while (rem)
    {
        const long before = ftell(f);
        uint8_t byte;

        if (before < 0)
        {
            LOG("%s: ftell(3) before: %s\n", __func__, strerror(errno));
            return -1;
        }
        else if (!fread(&byte, sizeof byte, 1, f))
        {
            LOG("%s: fread(3) failed, feof=%d, ferror=%d\n",
                __func__, feof(f), ferror(f));
            return -1;
        }
        else if (rem == 1 && byte != OP_END)
        {
            LOG("%s: unexpected opcode %#" PRIx8 " at body end\n",
                __func__, byte);
            return -1;
        }
        else if (interp_check_opcode(byte, f))
        {
            LOG("%s: interp_check_opcode failed\n", __func__);
            return -1;
        }

        const long after = ftell(f);

        if (after < 0)
        {
            LOG("%s: ftell(3) after: %s\n", __func__, strerror(errno));
            return -1;
        }

        rem -= after - before;
    }

    return 0;
}

static int check_type(FILE *const f)
{
    varint7 type;

    if (varint7_read(f, &type))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }

    return 0;
}

static int check_local(FILE *const f)
{
    varuint32 count;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }
    else if (check_type(f))
    {
        LOG("%s: check_type failed\n", __func__);
        return -1;
    }

    return 0;
}

static int check_locals(FILE *const f)
{
    varuint32 local_count;

    if (varuint32_read(f, &local_count))
    {
        LOG("%s: varuint32_read local_count failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < local_count; i++)
        if (check_local(f))
        {
            LOG("%s: check_local failed\n", __func__);
            return -1;
        }

    return 0;
}

static int check_function_body(FILE *const f)
{
    varuint32 body_size;

    if (varuint32_read(f, &body_size))
    {
        LOG("%s: varuint32_read body_size failed\n", __func__);
        return -1;
    }

    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3) start: %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check_locals(f))
    {
        LOG("%s: check_locals failed\n", __func__);
        return -1;
    }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3) end: %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long consumed = end - start;

    if (consumed > body_size)
    {
        LOG("%s: exceeded function body size\n", __func__);
        return -1;
    }
    else if (check_body(f, body_size - consumed))
    {
        LOG("%s: check_body failed\n", __func__);
        return -1;
    }

    /* TODO: add function body pointers to struct nanowasm. */
    return 0;
}

static int check_function_bodies(FILE *const f)
{
    varuint32 count;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < count; i++)
        if (check_function_body(f))
        {
            LOG("%s: check_function_body failed\n", __func__);
            return -1;
        }

    return 0;
}

static int check(FILE *const f, const unsigned long len)
{
    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check_function_bodies(f))
    {
        LOG("%s: check_function_bodies failed\n", __func__);
        return -1;
    }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long size = end - start;

    if (size != len)
    {
        LOG("%s: size exceeded (%lu expected, got %lu)\n",
                __func__, len, size);
        return -1;
    }

    return 0;
}

int section_code_check(const struct section *const s, struct nw_mod *const m,
    const unsigned long len)
{
    FILE *const f = s->f;

    if (m->sections.code)
    {
        LOG("%s: ignoring duplicate section\n", __func__);
        return fseek(f, len, SEEK_CUR);
    }

    const long offset = ftell(f);

    if (offset < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check(f, len))
    {
        LOG("%s: check failed\n", __func__);
        return -1;
    }

    m->sections.code = offset;
    return 0;
}