object-introspection/oi/Syscall.h

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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <algorithm>
#include <cstddef>
#include <cstdint>
extern "C" {
#include <fcntl.h>
#include <sys/syscall.h>
#include <sys/types.h>
}
namespace {
template <size_t N>
struct StringLiteral {
constexpr StringLiteral(const char (&str)[N]) {
std::copy_n(str, N, value);
}
char value[N];
};
} // namespace
/*
* The Syscall structure describes a `syscall(2)` in a generic manner.
* The struct is used by `OIDebugger::remoteSyscall` to define the return type
* and statically check the number of arguments being passed. Currently, I don't
* know how to use the _Args to also statically check the type of the arguments.
* In the meantime, I can use the size of _Args to do a simple count check.
*/
template <StringLiteral _Name,
unsigned long _SysNum,
typename _RetType,
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typename... _Args>
struct Syscall {
/* User friendly syscall name */
static constexpr auto Name = _Name.value;
/* The syscall's number (see <sys/syscall.h>) */
static constexpr unsigned long SysNum = _SysNum;
/* The syscall's return type */
using RetType = _RetType;
/* The number of arguments the syscall takes */
static constexpr size_t ArgsCount = sizeof...(_Args);
static_assert(ArgsCount <= 6,
"X64 syscalls support a maximum of 6 arguments");
};
/*
* The list of syscalls we want to be able to use on the remote process.
* The types passed to `struct Syscall` come directly from `man 2 <SYSCALL>`.
* Don't hesitate to expand this list if you need more syscalls!
*/
using SysOpen = Syscall<"open", SYS_open, int, const char*, int, mode_t>;
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using SysClose = Syscall<"close", SYS_close, int, int>;
using SysFsync = Syscall<"fsync", SYS_fsync, int, int>;
using SysMmap =
Syscall<"mmap", SYS_mmap, void*, void*, size_t, int, int, int, off_t>;
using SysMunmap = Syscall<"munmap", SYS_munmap, int, void*, size_t>;