serenity/Userland/Utilities/syscall.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/Iterator.h>
#include <AK/Vector.h>
#include <LibCore/ArgsParser.h>
#include <mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syscall.h>

#define SC_NARG 4

FlatPtr arg[SC_NARG];
char outbuf[BUFSIZ];

using Arguments = Vector<const char*>;
using ArgIter = Arguments::Iterator;

static FlatPtr parse_from(ArgIter&);

int main(int argc, char** argv)
{
    bool output_buffer = false;
    bool list_syscalls = false;
    Vector<const char*> arguments;

    Core::ArgsParser args_parser;
    args_parser.add_option(output_buffer, "Output the contents of the buffer (beware of stray zero bytes!)", "output-buffer", 'o');
    args_parser.add_option(list_syscalls, "List all existing syscalls", "list-syscalls", 'l');
    args_parser.add_positional_argument(arguments, "Syscall arguments; can be a string, 'buf' for the output buffer, or numbers like 1234 or 0xffffffff, or a buffer that must begin with '[' and end with ']'. If the first character is ',' (comma), the argument is interpreted as a string, no matter what. This is useful if the string is '[' or '0x0'.", "syscall-arguments");
    args_parser.parse(argc, argv);

    ArgIter iter = arguments.begin();
    for (size_t i = 0; i < SC_NARG && !iter.is_end(); i++) {
        arg[i] = parse_from(iter);
    }
    if (!iter.is_end()) {
        fprintf(stderr, "Too many arguments (did you want to use '[ parameter buffers ]'?)\n");
        return -1;
    }

    if (arg[0] > Syscall::Function::__Count) {
        for (int sc = 0; sc < Syscall::Function::__Count; ++sc) {
            if (strcmp(Syscall::to_string((Syscall::Function)sc), (char*)arg[0]) == 0) {
                arg[0] = sc;
                break;
            }
        }
        if (arg[0] > Syscall::Function::__Count) {
            fprintf(stderr, "Invalid syscall entry %s\n", (char*)arg[0]);
            return -1;
        }
    }

    int rc = syscall(arg[0], arg[1], arg[2], arg[3]);
    if (rc == -1)
        perror("syscall");
    if (output_buffer)
        fwrite(outbuf, 1, sizeof(outbuf), stdout);

    fprintf(stderr, "Syscall return: %d\n", rc);
    return 0;
}

static FlatPtr as_buf(Vector<FlatPtr> params_vec)
{
    size_t params_size = sizeof(FlatPtr) * params_vec.size();
    size_t buf_size = round_up_to_power_of_two(params_size + 1, PAGE_SIZE);
    void* buf = mmap(nullptr, buf_size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, 0, 0);
    if (buf == MAP_FAILED) {
        fprintf(stderr, "Warning: Could not allocate buffer of size %zu (low memory?)\n", buf_size);
        exit(1);
    }
    // It's probably good to ensure zero-initialization.
    memset(buf, 0, buf_size);
    memcpy(buf, params_vec.data(), params_size);
    // Leak the buffer here. We need to keep it until the special syscall happens,
    // and we terminate immediately afterwards anyway.
    return (FlatPtr)buf;
}

static FlatPtr parse_parameter_buffer(ArgIter& iter)
{
    Vector<FlatPtr> params_vec;
    while (!iter.is_end()) {
        if (strcmp(*iter, "]") == 0) {
            ++iter;
            return as_buf(params_vec);
        }

        params_vec.append(parse_from(iter));
    }

    fprintf(stderr, "Warning: Treating unmatched ']' as literal string\n");
    exit(1);
    ASSERT_NOT_REACHED();
}

static FlatPtr parse_from(ArgIter& iter)
{
    const char* this_arg = *iter;
    ++iter;

    // Is it a forced literal?
    if (this_arg[0] == ',')
        return (FlatPtr)(this_arg + 1);

    // Is it the output buffer?
    if (strcmp(this_arg, "buf") == 0)
        return (FlatPtr)outbuf;

    // Is it a parameter buffer?
    if (strcmp(this_arg, "[") == 0)
        return parse_parameter_buffer(iter);

    // Is it a number?
    char* endptr = nullptr;
    FlatPtr l = strtoul(this_arg, &endptr, 0);
    if (*endptr == 0) {
        return l;
    }

    // Then it must be a string:
    if (strcmp(this_arg, "]") == 0)
        fprintf(stderr, "Warning: Treating unmatched ']' as literal string\n");

    return (FlatPtr)this_arg;
}