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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sandbox/linux/bpf_dsl/syscall_set.h"
#include <stdint.h>
#include "base/logging.h"
#include "base/macros.h"
#include "sandbox/linux/bpf_dsl/linux_syscall_ranges.h"
namespace sandbox {
namespace {
#if defined(__mips__) && (_MIPS_SIM == _MIPS_SIM_ABI32)
// This is true for Mips O32 ABI.
static_assert(MIN_SYSCALL == __NR_Linux, "min syscall number should be 4000");
#else
// This true for supported architectures (Intel and ARM EABI).
static_assert(MIN_SYSCALL == 0u,
"min syscall should always be zero");
#endif
// SyscallRange represents an inclusive range of system call numbers.
struct SyscallRange {
uint32_t first;
uint32_t last;
};
const SyscallRange kValidSyscallRanges[] = {
// First we iterate up to MAX_PUBLIC_SYSCALL, which is equal to MAX_SYSCALL
// on Intel architectures, but leaves room for private syscalls on ARM.
{MIN_SYSCALL, MAX_PUBLIC_SYSCALL},
#if defined(__arm__)
// ARM EABI includes "ARM private" system calls starting at
// MIN_PRIVATE_SYSCALL, and a "ghost syscall private to the kernel" at
// MIN_GHOST_SYSCALL.
{MIN_PRIVATE_SYSCALL, MAX_PRIVATE_SYSCALL},
{MIN_GHOST_SYSCALL, MAX_SYSCALL},
#endif
};
} // namespace
SyscallSet::Iterator SyscallSet::begin() const {
return Iterator(set_, false);
}
SyscallSet::Iterator SyscallSet::end() const {
return Iterator(set_, true);
}
bool SyscallSet::IsValid(uint32_t num) {
for (const SyscallRange& range : kValidSyscallRanges) {
if (num >= range.first && num <= range.last) {
return true;
}
}
return false;
}
bool operator==(const SyscallSet& lhs, const SyscallSet& rhs) {
return (lhs.set_ == rhs.set_);
}
SyscallSet::Iterator::Iterator(Set set, bool done)
: set_(set), done_(done), num_(0) {
// If the set doesn't contain 0, we need to skip to the next element.
if (!done && set_ == (IsValid(num_) ? Set::INVALID_ONLY : Set::VALID_ONLY)) {
++*this;
}
}
uint32_t SyscallSet::Iterator::operator*() const {
DCHECK(!done_);
return num_;
}
SyscallSet::Iterator& SyscallSet::Iterator::operator++() {
DCHECK(!done_);
num_ = NextSyscall();
if (num_ == 0) {
done_ = true;
}
return *this;
}
// NextSyscall returns the next system call in the iterated system
// call set after |num_|, or 0 if no such system call exists.
uint32_t SyscallSet::Iterator::NextSyscall() const {
const bool want_valid = (set_ != Set::INVALID_ONLY);
const bool want_invalid = (set_ != Set::VALID_ONLY);
for (const SyscallRange& range : kValidSyscallRanges) {
if (want_invalid && range.first > 0 && num_ < range.first - 1) {
// Even when iterating invalid syscalls, we only include the end points;
// so skip directly to just before the next (valid) range.
return range.first - 1;
}
if (want_valid && num_ < range.first) {
return range.first;
}
if (want_valid && num_ < range.last) {
return num_ + 1;
}
if (want_invalid && num_ <= range.last) {
return range.last + 1;
}
}
if (want_invalid) {
// BPF programs only ever operate on unsigned quantities. So,
// that's how we iterate; we return values from
// 0..0xFFFFFFFFu. But there are places, where the kernel might
// interpret system call numbers as signed quantities, so the
// boundaries between signed and unsigned values are potential
// problem cases. We want to explicitly return these values from
// our iterator.
if (num_ < 0x7FFFFFFFu)
return 0x7FFFFFFFu;
if (num_ < 0x80000000u)
return 0x80000000u;
if (num_ < 0xFFFFFFFFu)
return 0xFFFFFFFFu;
}
return 0;
}
bool operator==(const SyscallSet::Iterator& lhs,
const SyscallSet::Iterator& rhs) {
DCHECK(lhs.set_ == rhs.set_);
return (lhs.done_ == rhs.done_) && (lhs.num_ == rhs.num_);
}
bool operator!=(const SyscallSet::Iterator& lhs,
const SyscallSet::Iterator& rhs) {
return !(lhs == rhs);
}
} // namespace sandbox
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