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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Debug.h>
#include <AK/Iterator.h>
#include <AK/Vector.h>
#include <LibCore/ArgsParser.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.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&);
template<>
struct AK::Formatter<Syscall::Function> : Formatter<StringView> {
void format(FormatBuilder& builder, Syscall::Function function)
{
return Formatter<StringView>::format(builder, to_string(function));
}
};
int main(int argc, char** argv)
{
bool output_buffer = false;
bool list_syscalls = false;
Vector<const char*> arguments;
Core::ArgsParser args_parser;
args_parser.set_general_help(
"Enables you to do a direct syscall, even those that use a 'SC_*_params' buffer.\n"
"Arguments can be literal strings, numbers, the output buffer, or parameter buffers:\n"
" - Arguments that begin with a comma are stripped of the comma and treated as string arguments, for example ',0x0' or ',['.\n"
" - 'buf' is replaced by a pointer to the output buffer.\n"
" - Numbers can be written like 1234 or 0xDEADC0DE.\n"
" - Parameter buffer (e.g. SC_realpath_params) can be passed by wrapping them in '[' and ']'. Note that '[' and ']' must be separate arguments to syscall(1). Buffers can be used recursively.\n"
" - The first argument may also be any syscall function name. Run 'syscall -l' to see the list.\n"
" - Arguments that cannot be interpreted are treated as string arguments, for example 'Hello, friends!'.\n"
"\n"
"Full example: syscall -o realpath [ /usr/share/man/man2/getgid.md 1024 buf 1024 ]");
args_parser.add_option(list_syscalls, "List all existing syscalls, and exit", "list-syscalls", 'l');
args_parser.add_option(output_buffer, "Output the contents of the buffer (beware of stray zero bytes!)", "output-buffer", 'o');
args_parser.add_positional_argument(arguments, "Syscall arguments; see general help.", "syscall-arguments", Core::ArgsParser::Required::No);
args_parser.parse(argc, argv);
if (list_syscalls) {
outln("syscall list:");
for (int sc = 0; sc < Syscall::Function::__Count; ++sc) {
outln(" \033[33;1m{}\033[0m - {}", sc, static_cast<Syscall::Function>(sc));
}
exit(0);
}
if (arguments.is_empty()) {
args_parser.print_usage(stderr, argv[0]);
exit(1);
}
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()) {
warnln("Too many arguments (did you want to use '[ parameter buffers ]'?)");
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) {
warnln("Invalid syscall entry {}", (char*)arg[0]);
return -1;
}
}
dbgln_if(SYSCALL_1_DEBUG, "Calling {} {:p} {:p} {:p}\n", arg[0], arg[1], arg[2], arg[3]);
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);
warnln("Syscall return: {}", 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);
if constexpr (SYSCALL_1_DEBUG) {
StringBuilder builder;
builder.append("Prepared [");
for (size_t i = 0; i < params_vec.size(); ++i) {
builder.appendff(" {:p}", params_vec[i]);
}
builder.appendff(" ] at {:p}", (FlatPtr)buf);
dbgln("{}", builder.to_string());
}
// 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, "Error: Unmatched '['?!\n");
exit(1);
VERIFY_NOT_REACHED();
}
static FlatPtr parse_from(ArgIter& iter)
{
const char* this_arg = *iter;
++iter;
// Is it a forced literal?
if (this_arg[0] == ',') {
this_arg += 1;
dbgln_if(SYSCALL_1_DEBUG, "Using (forced) string >>{}<< at {:p}", this_arg, (FlatPtr)this_arg);
return (FlatPtr)this_arg;
}
// 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");
dbgln_if(SYSCALL_1_DEBUG, "Using (detected) string >>{}<< at {:p}", this_arg, (FlatPtr)this_arg);
return (FlatPtr)this_arg;
}
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