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AnyPS5/core/libs/tests/WriteWatch.cpp
T
Nicolas GonzalezandClaude Opus 5.5 671c14acba fix(libc): bound untrapped read retries per untrap when the cache spills 
The per-thread retry entries are a 64-entry cache. More threads faulting in
turn on a page whose protection does not explain the fault evict each
other's entries before their next attempt, so each count restarted at 1 and
the faults were retried forever. Retries between two untraps are now also
counted in total, up to 64 times the per-thread budget.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
2026-11-01 07:33:03 +01:00

824 lines
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#include "prx/libc/include/GuestWriteWatch.hpp"
#include <algorithm>
#include <array>
#include <atomic>
#include <cerrno>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <mutex>
#include <set>
#include <stdexcept>
#include <string>
#include <string_view>
#include <thread>
#include <utility>
#include <vector>
#include <mach/mach.h>
#include <mach/mach_vm.h>
#include <mach/ndr.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
#if !defined(__APPLE__)
#error The page protection write watch is the macOS backend
#endif
using namespace GuestWriteWatch;
namespace {
void Require(bool condition, const char* message) {
if (!condition) throw std::runtime_error(message);
}
struct Region {
explicit Region(std::size_t pageCount) : page(static_cast<std::size_t>(::getpagesize())), bytes(pageCount * page) {
base = static_cast<std::uint8_t*>(::mmap(nullptr, bytes, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0));
Require(base != MAP_FAILED, "cannot map the test region");
}
~Region() {
GuestWriteWatchUnregister_nid_postfix(base, bytes);
::munmap(base, bytes);
}
std::uintptr_t Address(std::size_t index) const {
return reinterpret_cast<std::uintptr_t>(base) + index * page;
}
using Collector = bool (*)(std::uintptr_t, std::size_t, void (*)(void*, std::uintptr_t, std::uintptr_t), void*);
std::set<std::size_t> Collect(Collector collector = &GuestWriteWatchCollect_nid_postfix, std::size_t first = 0, std::size_t count = 0) {
std::set<std::size_t> pages;
struct Sink {
Region* region;
std::set<std::size_t>* pages;
} sink{this, &pages};
const bool complete = collector(Address(first), count == 0 ? bytes - first * page : count * page, [](void* context, std::uintptr_t begin, std::uintptr_t end) {
auto& target = *static_cast<Sink*>(context);
for (auto at = begin; at < end; at += target.region->page) target.pages->insert((at - target.region->Address(0)) / target.region->page);
}, &sink);
Require(complete, "collection of a watched range is incomplete");
return pages;
}
std::size_t page;
std::size_t bytes;
std::uint8_t* base = nullptr;
};
std::set<std::size_t> All(std::size_t count) {
std::set<std::size_t> pages;
for (std::size_t index = 0; index < count; ++index) pages.insert(index);
return pages;
}
void CheckCollect() {
Region region(8);
Require(GuestWriteWatchAvailable_nid_postfix(), "write watch is unavailable");
Require(!GuestWriteWatchCovers_nid_postfix(region.Address(0), region.bytes), "unregistered range is covered");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(GuestWriteWatchCovers_nid_postfix(region.Address(0), region.bytes), "registered range is not covered");
Require(region.Collect() == All(8), "a new range is not reported in full");
Require(region.Collect().empty(), "an untouched range reports writes");
region.base[3 * region.page + 17] = 1;
region.base[5 * region.page] = 2;
region.base[5 * region.page + 9] = 3;
Require(region.Collect() == std::set<std::size_t>({3, 5}), "written pages are not reported exactly");
Require(region.Collect().empty(), "collected writes are reported again");
Require(region.base[3 * region.page + 17] == 1 && region.base[5 * region.page + 9] == 3, "watched writes were lost");
std::memset(region.base + region.page - 4, 7, 8);
Require(region.Collect() == std::set<std::size_t>({0, 1}), "a write across a page boundary is not reported on both pages");
}
void CheckFresh() {
Region region(8);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect(&GuestWriteWatchCollect_nid_postfix, 0, 4) == All(4), "the collected half is not reported in full");
region.base[region.page] = 1;
Require(region.Collect(&GuestWriteWatchCollectFresh_nid_postfix) == std::set<std::size_t>({4, 5, 6, 7}), "a fresh collection does not report exactly the never collected pages");
Require(region.Collect(&GuestWriteWatchCollectFresh_nid_postfix).empty(), "a fresh collection reports pages again");
region.base[6 * region.page] = 1;
Require(region.Collect() == std::set<std::size_t>({1, 6}), "a fresh collection does not arm the pages it reports");
Require(region.Collect().empty(), "collected writes are reported again");
}
void CheckArmed() {
Region region(8);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect(&GuestWriteWatchCollect_nid_postfix, 0, 4) == All(4), "the collected half is not reported in full");
region.base[region.page] = 1;
region.base[6 * region.page] = 1;
Require(region.Collect(&GuestWriteWatchCollectArmed_nid_postfix) == std::set<std::size_t>({1}), "an armed collection does not report exactly the written armed pages");
Require(region.Collect() == std::set<std::size_t>({4, 5, 6, 7}), "an armed collection takes never collected pages");
Require(region.Collect().empty(), "collected writes are reported again");
}
void CheckRegisterAgain() {
Region region(4);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(4), "a new range is not reported in full");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(4), "a range registered again is not reported in full");
region.base[2 * region.page] = 1;
Require(region.Collect() == std::set<std::size_t>({2}), "a range registered while protected stops reporting writes");
GuestWriteWatchRegister_nid_postfix(region.base + region.page, region.page);
Require(region.Collect() == std::set<std::size_t>({1}), "registering part of a range does not report that part alone");
region.base[0] = 1;
region.base[3 * region.page] = 1;
Require(region.Collect() == std::set<std::size_t>({0, 3}), "the rest of a split range stops reporting writes");
}
int KernelProtection(const void* page) {
mach_vm_address_t address = reinterpret_cast<mach_vm_address_t>(page);
mach_vm_size_t size = 0;
vm_region_basic_info_data_64_t info{};
mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
mach_port_t object = MACH_PORT_NULL;
Require(mach_vm_region(mach_task_self(), &address, &size, VM_REGION_BASIC_INFO_64, reinterpret_cast<vm_region_info_t>(&info), &count, &object) == KERN_SUCCESS && address == reinterpret_cast<mach_vm_address_t>(page), "cannot read the kernel protection of a page");
return ((info.protection & VM_PROT_READ) ? PROT_READ : 0) | ((info.protection & VM_PROT_WRITE) ? PROT_WRITE : 0) | ((info.protection & VM_PROT_EXECUTE) ? PROT_EXEC : 0);
}
void CheckRegisterMapped() {
Region region(4);
std::uintptr_t runEnd = 0;
Require(::mprotect(region.base, region.bytes, PROT_NONE) == 0, "cannot reserve the test region");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(::mmap(region.base, region.bytes, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0) == region.base, "cannot map over the reservation");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(GuestWriteWatchProtection_nid_postfix(region.Address(0), region.Address(4), &runEnd) == (PROT_READ | PROT_WRITE) && runEnd == region.Address(4), "a range mapped over its reservation keeps the reservation's protection");
Require(region.Collect() == All(4), "a mapped range is not reported in full");
region.base[2 * region.page] = 1;
Require(region.Collect() == std::set<std::size_t>({2}), "a range mapped over its reservation stops reporting writes");
Require(::mmap(region.base + region.page, region.page, PROT_NONE, MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0) == region.base + region.page, "cannot reserve a watched page again");
GuestWriteWatchRegister_nid_postfix(region.base + region.page, region.page);
Require(GuestWriteWatchProtection_nid_postfix(region.Address(1), region.Address(2), &runEnd) == PROT_NONE, "a protected page reserved again reports its old protection");
Require(KernelProtection(region.base + region.page) == PROT_NONE, "registering a protected page reserved again restored its old protection");
}
void CheckHostWrite() {
Region region(4);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(4), "a new range is not reported in full");
int descriptors[2];
Require(::pipe(descriptors) == 0, "cannot create a pipe");
const std::array<char, 8> payload{'w', 'a', 't', 'c', 'h', 'e', 'd', '!'};
Require(::write(descriptors[1], payload.data(), payload.size()) == static_cast<ssize_t>(payload.size()), "cannot fill the pipe");
errno = 0;
Require(::read(descriptors[0], region.base + region.page, payload.size()) == -1 && errno == EFAULT, "a system call wrote a protected page without a host write");
GuestWriteWatchBeginHostWrite_nid_postfix(region.base + region.page, payload.size());
Require(region.Collect() == std::set<std::size_t>({1}), "a page under a host write is not reported");
Require(::read(descriptors[0], region.base + region.page, payload.size()) == static_cast<ssize_t>(payload.size()), "a collection protected a page during a host write");
GuestWriteWatchEndHostWrite_nid_postfix(region.base + region.page, payload.size());
Require(std::memcmp(region.base + region.page, payload.data(), payload.size()) == 0, "the host write did not reach the page");
Require(region.Collect() == std::set<std::size_t>({1}), "a host write is not reported after it ends");
Require(region.Collect().empty(), "a finished host write is reported again");
::close(descriptors[0]);
::close(descriptors[1]);
}
void CheckEmptyRanges() {
Region region(1);
for (const auto offset : {std::size_t{0}, std::size_t{1}, region.page - 1}) {
auto* pointer = region.base + offset;
GuestWriteWatchRegister_nid_postfix(pointer, 0);
Require(!GuestWriteWatchCovers_nid_postfix(region.Address(0), region.bytes), "an empty registration watches a page");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(1), "a new range is not reported in full");
Require(!GuestWriteWatchUnregister_nid_postfix(pointer, 0), "an empty unregister removes a page");
Require(GuestWriteWatchCovers_nid_postfix(region.Address(0), region.bytes), "an empty unregister changes coverage");
GuestWriteWatchRegister_nid_postfix(pointer, 0);
Require(region.Collect().empty(), "an empty registration marks a watched page fresh");
GuestWriteWatchBeginHostWrite_nid_postfix(pointer, 0);
Require(KernelProtection(region.base) == PROT_READ, "an empty host write unprotects a page");
Require(region.Collect().empty(), "an empty host write reports a dirty page");
GuestWriteWatchEndHostWrite_nid_postfix(pointer, 0);
GuestWriteWatchBeginHostWrite_nid_postfix(pointer, 1);
GuestWriteWatchEndHostWrite_nid_postfix(pointer, 0);
Require(region.Collect() == All(1), "an active host write is not reported");
Require(KernelProtection(region.base) == (PROT_READ | PROT_WRITE), "an empty end host write releases an active host write");
GuestWriteWatchEndHostWrite_nid_postfix(pointer, 1);
Require(region.Collect() == All(1), "a finished host write is not reported");
Require(region.Collect().empty(), "a finished host write is reported again");
GuestWriteWatchProtectionChanged_nid_postfix(pointer, 0, PROT_NONE);
std::uintptr_t runEnd = 0;
Require(GuestWriteWatchProtection_nid_postfix(region.Address(0), region.Address(1), &runEnd) == (PROT_READ | PROT_WRITE), "an empty protection change changes the recorded protection");
Require(region.Collect().empty(), "an empty protection change reports a dirty page");
region.base[offset] = 1;
Require(region.Collect() == All(1), "an empty range operation prevents a later write from being tracked");
Require(GuestWriteWatchUnregister_nid_postfix(region.base, region.bytes), "cannot unregister the test region");
}
}
void CheckNonWriteFaults(bool execute) {
Region region(1);
#if defined(__aarch64__)
const std::uint32_t returnInstruction = 0xd65f03c0;
std::memcpy(region.base, &returnInstruction, sizeof(returnInstruction));
#elif defined(__x86_64__)
region.base[0] = 0xc3;
#endif
for (const bool armed : {false, true}) {
for (const bool hostWrite : {false, true}) {
const auto child = ::fork();
Require(child >= 0, "cannot fork a faulting child");
if (child == 0) {
::alarm(2);
if (!execute) {
char path[] = "/tmp/anyps5-write-watch-XXXXXX";
const int file = ::mkstemp(path);
if (file < 0) ::_exit(2);
::unlink(path);
if (::ftruncate(file, region.bytes) != 0) ::_exit(2);
if (::mmap(region.base, region.bytes, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, file, 0) != region.base) ::_exit(2);
if (::ftruncate(file, 0) != 0) ::_exit(2);
::close(file);
}
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
if (armed) static_cast<void>(region.Collect());
if (hostWrite) GuestWriteWatchBeginHostWrite_nid_postfix(region.base, region.bytes);
if (execute) reinterpret_cast<void (*)()>(region.base)();
else {
const volatile auto value = *static_cast<volatile std::uint8_t*>(region.base);
static_cast<void>(value);
}
::_exit(3);
}
int status = 0;
Require(::waitpid(child, &status, 0) == child, "cannot wait for a faulting child");
Require(WIFSIGNALED(status) && (WTERMSIG(status) == SIGBUS || WTERMSIG(status) == SIGSEGV), execute ? "a non-executable watched page did not deliver its fault" : "a watched mapping with missing backing did not deliver its read fault");
}
}
}
void CheckProtection() {
Region region(6);
std::uintptr_t runEnd = 0;
Require(GuestWriteWatchProtection_nid_postfix(region.Address(0), region.Address(6), &runEnd) == -1 && runEnd == region.Address(6), "an unwatched range reports a protection");
GuestWriteWatchRegister_nid_postfix(region.base + 2 * region.page, 3 * region.page);
Require(GuestWriteWatchProtection_nid_postfix(region.Address(0), region.Address(6), &runEnd) == -1 && runEnd == region.Address(2), "the run before a watched range does not end at it");
static_cast<void>(GuestWriteWatchCollect_nid_postfix(region.Address(2), 3 * region.page, [](void*, std::uintptr_t, std::uintptr_t) {}, nullptr));
Require(GuestWriteWatchProtection_nid_postfix(region.Address(2), region.Address(6), &runEnd) == (PROT_READ | PROT_WRITE) && runEnd == region.Address(5), "a protected page does not report the protection it was given");
Require(::mprotect(region.base + 3 * region.page, region.page, PROT_READ) == 0, "cannot change the protection");
GuestWriteWatchProtectionChanged_nid_postfix(region.base + 3 * region.page, region.page, PROT_READ);
Require(GuestWriteWatchProtection_nid_postfix(region.Address(2), region.Address(6), &runEnd) == (PROT_READ | PROT_WRITE) && runEnd == region.Address(3), "a run does not end where the protection changes");
Require(GuestWriteWatchProtection_nid_postfix(region.Address(3), region.Address(6), &runEnd) == PROT_READ && runEnd == region.Address(4), "a changed protection is not reported");
std::set<std::size_t> pages;
static_cast<void>(GuestWriteWatchCollect_nid_postfix(region.Address(2), 3 * region.page, [](void* context, std::uintptr_t begin, std::uintptr_t) { static_cast<std::set<std::size_t>*>(context)->insert(begin); }, &pages));
Require(pages == std::set<std::size_t>({region.Address(3)}), "a protection change is not reported as a write");
Require(::mprotect(region.base + 3 * region.page, region.page, PROT_READ | PROT_WRITE) == 0, "cannot restore the protection");
GuestWriteWatchProtectionChanged_nid_postfix(region.base + 3 * region.page, region.page, PROT_READ | PROT_WRITE);
region.base[3 * region.page] = 1;
GuestWriteWatchUnregister_nid_postfix(region.base + 2 * region.page, 3 * region.page);
region.base[2 * region.page] = 1;
region.base[4 * region.page] = 1;
Require(!GuestWriteWatchCovers_nid_postfix(region.Address(2), region.page), "an unregistered range is covered");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
static_cast<void>(region.Collect());
Require(GuestWriteWatchProtect_nid_postfix(region.base, region.page, PROT_READ) == 0, "cannot protect a watched page");
Require(KernelProtection(region.base) == PROT_READ, "a protect does not change the host protection");
Require(GuestWriteWatchProtection_nid_postfix(region.Address(0), region.Address(6), &runEnd) == PROT_READ && runEnd == region.Address(1), "a protect is not recorded");
Require(region.Collect() == std::set<std::size_t>({0}), "a protect is not reported as a write");
Require(GuestWriteWatchProtect_nid_postfix(region.base, region.page, PROT_READ | PROT_WRITE) == 0, "cannot restore a watched page");
static_cast<void>(region.Collect());
region.base[0] = 1;
Require(region.Collect() == std::set<std::size_t>({0}), "a write after a protect is not reported");
Require(GuestWriteWatchProtect_nid_postfix(region.base + 1, region.page, PROT_READ) == EINVAL, "a misaligned protect does not fail with EINVAL");
}
void CheckOverlaps() {
Region region(6);
Require(!GuestWriteWatchOverlaps_nid_postfix(region.Address(0), region.bytes), "an unregistered range overlaps the watch");
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(GuestWriteWatchUnregister_nid_postfix(region.base, region.page), "cannot unregister the first page");
Require(GuestWriteWatchUnregister_nid_postfix(region.base + 3 * region.page, 3 * region.page), "cannot unregister the last pages");
Require(!GuestWriteWatchCovers_nid_postfix(region.Address(0), region.bytes), "a range around unregistered pages is covered");
Require(GuestWriteWatchOverlaps_nid_postfix(region.Address(0), region.bytes), "a range around registered pages does not overlap the watch");
Require(GuestWriteWatchOverlaps_nid_postfix(region.Address(1) - 1, 2), "a range ending in a registered page does not overlap the watch");
Require(GuestWriteWatchOverlaps_nid_postfix(region.Address(3) - 1, 2), "a range starting in a registered page does not overlap the watch");
Require(!GuestWriteWatchOverlaps_nid_postfix(region.Address(0), region.page), "an unregistered page before the registered ones overlaps the watch");
Require(!GuestWriteWatchOverlaps_nid_postfix(region.Address(3), 3 * region.page), "unregistered pages after the registered ones overlap the watch");
Require(!GuestWriteWatchOverlaps_nid_postfix(region.Address(1), 0), "an empty range overlaps the watch");
}
void CheckThreads() {
constexpr std::size_t Threads = 4;
constexpr std::size_t PagesPerThread = 64;
constexpr int Rounds = 50;
Region region(Threads * PagesPerThread);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(Threads * PagesPerThread), "a new range is not reported in full");
std::atomic<bool> start{false};
std::atomic<std::size_t> finished{0};
std::array<std::thread, Threads> writers;
for (std::size_t thread = 0; thread < Threads; ++thread) {
writers[thread] = std::thread([&, thread] {
while (!start.load()) std::this_thread::yield();
for (int round = 1; round <= Rounds; ++round)
for (std::size_t index = 0; index < PagesPerThread; ++index) region.base[(thread * PagesPerThread + index) * region.page] = static_cast<std::uint8_t>(round);
finished.fetch_add(1);
});
}
std::vector<std::uint8_t> seen(Threads * PagesPerThread, 0);
const auto take = [&] {
for (const auto index : region.Collect()) seen[index] = region.base[index * region.page];
};
start.store(true);
while (finished.load() != Threads) {
take();
std::this_thread::yield();
}
for (auto& writer : writers) writer.join();
take();
for (std::size_t index = 0; index < seen.size(); ++index)
Require(seen[index] == static_cast<std::uint8_t>(Rounds), "a write that raced a collection was not reported");
Require(region.Collect().empty(), "writes are reported after the writers stopped");
}
int PageProtection(const void* page) {
mach_vm_address_t address = reinterpret_cast<mach_vm_address_t>(page);
mach_vm_size_t size = 0;
vm_region_basic_info_data_64_t info{};
mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
mach_port_t object = MACH_PORT_NULL;
Require(mach_vm_region(mach_task_self(), &address, &size, VM_REGION_BASIC_INFO_64, reinterpret_cast<vm_region_info_t>(&info), &count, &object) == KERN_SUCCESS && address <= reinterpret_cast<mach_vm_address_t>(page), "cannot read the kernel protection of a page");
return ((info.protection & VM_PROT_READ) ? PROT_READ : 0) | ((info.protection & VM_PROT_WRITE) ? PROT_WRITE : 0) | ((info.protection & VM_PROT_EXECUTE) ? PROT_EXEC : 0);
}
struct TrapLog {
std::mutex mutex;
std::vector<std::pair<std::uintptr_t, std::uintptr_t>> calls;
std::vector<std::thread::id> threads;
std::atomic<std::uint8_t> fill{0};
std::atomic<std::ptrdiff_t> alias{0};
std::atomic<bool> bracket{false};
};
TrapLog& Traps() {
static TrapLog log;
return log;
}
void ResolveTrap(std::uintptr_t begin, std::uintptr_t end) {
auto& log = Traps();
{
const std::lock_guard lock(log.mutex);
log.calls.emplace_back(begin, end);
log.threads.push_back(std::this_thread::get_id());
}
if (log.bracket) GuestWriteWatchBeginHostWrite_nid_postfix(reinterpret_cast<void*>(begin), end - begin);
std::memset(reinterpret_cast<void*>(begin + log.alias.load()), log.fill.load(), end - begin);
if (log.bracket) GuestWriteWatchEndHostWrite_nid_postfix(reinterpret_cast<void*>(begin), end - begin);
GuestWriteWatchReleaseReads_nid_postfix(begin, end - begin);
}
std::vector<std::pair<std::uintptr_t, std::uintptr_t>> TakeTrapCalls(std::vector<std::thread::id>* threads = nullptr) {
auto& log = Traps();
const std::lock_guard lock(log.mutex);
if (threads != nullptr) *threads = log.threads;
log.threads.clear();
return std::exchange(log.calls, {});
}
std::uint8_t ReadOnThread(const std::uint8_t* address, std::thread::id* reader = nullptr) {
std::uint8_t value = 0;
std::thread([&] {
value = *reinterpret_cast<const volatile std::uint8_t*>(address);
if (reader != nullptr) *reader = std::this_thread::get_id();
}).join();
return value;
}
void CheckReadTrap() {
::alarm(20);
Region region(10);
Region unregistered(1);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
Require(region.Collect() == All(10), "a new range is not reported in full");
const auto page = region.page;
Require(!GuestWriteWatchTrapReads_nid_postfix(region.Address(1), page), "a read trap was set without a resolver");
Require(GuestWriteWatchSetReadTrapResolver_nid_postfix(&ResolveTrap), "cannot set the read trap resolver");
Require(!GuestWriteWatchTrapReads_nid_postfix(unregistered.Address(0), page), "a read trap was set on unwatched memory");
Require(!GuestWriteWatchTrapReads_nid_postfix(region.Address(1), 0), "an empty read trap was set");
auto& log = Traps();
log.fill = 0xa5;
const auto begin = region.Address(1) + 100;
Require(GuestWriteWatchTrapReads_nid_postfix(begin, page), "cannot set a read trap");
Require(PageProtection(region.base + page) == PROT_NONE && PageProtection(region.base + 2 * page) == PROT_NONE, "a read trap does not take the access to its pages");
Require(PageProtection(region.base) == PROT_READ && PageProtection(region.base + 3 * page) == PROT_READ, "a read trap changes pages outside its range");
std::thread::id reader;
Require(ReadOnThread(region.base + page + 105, &reader) == 0xa5, "a read of a trapped page does not see the resolver's bytes");
std::vector<std::thread::id> threads;
Require(TakeTrapCalls(&threads) == std::vector<std::pair<std::uintptr_t, std::uintptr_t>>{{begin, begin + page}}, "a trapped read does not resolve its range exactly once");
Require(threads.size() == 1 && threads[0] != reader && threads[0] != std::this_thread::get_id(), "a trapped read is not resolved on the resolver thread");
Require(PageProtection(region.base + page) == (PROT_READ | PROT_WRITE) && PageProtection(region.base + 2 * page) == (PROT_READ | PROT_WRITE), "the resolver's writes to its resolved pages are not let through");
Require(ReadOnThread(region.base + 2 * page) == 0xa5 && TakeTrapCalls().empty(), "a resolved read trap resolves again");
Require(region.Collect() == std::set<std::size_t>({1, 2}), "the resolver's writes are not reported");
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(3), page) && GuestWriteWatchTrapReads_nid_postfix(region.Address(3), page), "cannot set a read trap twice");
GuestWriteWatchReleaseReads_nid_postfix(region.Address(3), page);
Require(PageProtection(region.base + 3 * page) == PROT_READ, "a released read trap set twice does not give back the watch's protection");
Require(ReadOnThread(region.base + 3 * page) == 0 && TakeTrapCalls().empty(), "a released read trap resolves");
log.fill = 0x11;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(4), page), "cannot set a read trap");
region.base[4 * page] = 0x77;
Require(region.base[4 * page] == 0x77 && region.base[4 * page + 1] == 0x11, "a write to a trapped page does not land after the resolver's bytes");
Require(TakeTrapCalls().size() == 1, "a write to a trapped page does not resolve it once");
Require(region.Collect() == std::set<std::size_t>({4}), "a write to a trapped page is not reported");
region.base[5 * page] = 1;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(5), page), "cannot set a read trap");
Require(region.Collect() == std::set<std::size_t>({5}), "a written trapped page is not reported");
Require(PageProtection(region.base + 5 * page) == PROT_NONE, "a collection gives back the access to a trapped page");
Require(ReadOnThread(region.base + 5 * page) == 0x11 && TakeTrapCalls().size() == 1, "a trapped page read after a collection is not resolved");
log.fill = 0x22;
const auto half = page / 2;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(6), half), "cannot set a read trap");
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(6) + half, page), "cannot set a read trap");
GuestWriteWatchReleaseReads_nid_postfix(region.Address(6), half);
Require(PageProtection(region.base + 6 * page) == PROT_NONE, "releasing one read trap gives back a page another one still traps");
Require(ReadOnThread(region.base + 6 * page) == 0, "a page shared by two read traps does not keep the released trap's bytes");
Require(TakeTrapCalls() == std::vector<std::pair<std::uintptr_t, std::uintptr_t>>{{region.Address(6) + half, region.Address(7) + half}}, "a read of a shared page does not resolve exactly the trap still set");
log.fill = 0x33;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(8), page), "cannot set a read trap");
GuestWriteWatchBeginHostWrite_nid_postfix(region.base + 8 * page, 8);
Require(TakeTrapCalls(&threads).size() == 1 && threads[0] == std::this_thread::get_id(), "a host write over a trapped page does not resolve it first on its own thread");
Require(!GuestWriteWatchTrapReads_nid_postfix(region.Address(8), page), "a read trap was set under a host write");
int descriptors[2];
Require(::pipe(descriptors) == 0, "cannot create a pipe");
const std::array<char, 8> payload{'t', 'r', 'a', 'p', 'p', 'e', 'd', '!'};
Require(::write(descriptors[1], payload.data(), payload.size()) == static_cast<ssize_t>(payload.size()), "cannot fill the pipe");
Require(::read(descriptors[0], region.base + 8 * page, payload.size()) == static_cast<ssize_t>(payload.size()), "a system call cannot write a page whose read trap a host write resolved");
GuestWriteWatchEndHostWrite_nid_postfix(region.base + 8 * page, 8);
::close(descriptors[0]);
::close(descriptors[1]);
Require(std::memcmp(region.base + 8 * page, payload.data(), payload.size()) == 0 && region.base[8 * page + 8] == 0x33, "a host write over a resolved trap lost bytes");
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(9), page), "cannot set a read trap");
Require(GuestWriteWatchProtect_nid_postfix(region.base + 9 * page, page, PROT_READ) == 0, "cannot protect a trapped page");
Require(TakeTrapCalls().size() == 1 && PageProtection(region.base + 9 * page) == PROT_READ, "a protect of a trapped page does not resolve it and apply the new protection");
log.fill = 0x44;
log.bracket = true;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(3), page), "cannot set a read trap");
Require(ReadOnThread(region.base + 3 * page) == 0x44 && TakeTrapCalls().size() == 1, "a resolver that brackets its stores as a host write does not resolve its trap");
log.bracket = false;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(0), page), "cannot set a read trap");
Require(GuestWriteWatchUnregister_nid_postfix(region.base, region.bytes), "cannot unregister the test region");
Require(PageProtection(region.base) == (PROT_READ | PROT_WRITE), "unregistering a trapped page does not give back its protection");
Require(ReadOnThread(region.base) == 0 && TakeTrapCalls().empty(), "an unregistered read trap resolves");
::alarm(0);
}
void CheckReadTrapFaults() {
const auto bytes = static_cast<std::size_t>(::getpagesize());
for (const bool resolved : {false, true}) {
const auto child = ::fork();
Require(child >= 0, "cannot fork a faulting child");
if (child == 0) {
::alarm(2);
Region trapped(1);
GuestWriteWatchRegister_nid_postfix(trapped.base, trapped.bytes);
if (!GuestWriteWatchSetReadTrapResolver_nid_postfix(&ResolveTrap) || !GuestWriteWatchTrapReads_nid_postfix(trapped.Address(0), trapped.page)) ::_exit(2);
if (resolved) static_cast<void>(*reinterpret_cast<const volatile std::uint8_t*>(trapped.base));
char path[] = "/tmp/anyps5-write-watch-XXXXXX";
const int file = ::mkstemp(path);
if (file < 0) ::_exit(2);
::unlink(path);
if (::ftruncate(file, static_cast<off_t>(bytes)) != 0) ::_exit(2);
auto* mapped = static_cast<std::uint8_t*>(::mmap(nullptr, bytes, PROT_READ | PROT_WRITE, MAP_SHARED, file, 0));
if (mapped == MAP_FAILED || ::ftruncate(file, 0) != 0) ::_exit(2);
::close(file);
GuestWriteWatchRegister_nid_postfix(mapped, bytes);
static_cast<void>(*reinterpret_cast<const volatile std::uint8_t*>(mapped));
::_exit(3);
}
int status = 0;
Require(::waitpid(child, &status, 0) == child, "cannot wait for a faulting child");
Require(WIFSIGNALED(status) && (WTERMSIG(status) == SIGBUS || WTERMSIG(status) == SIGSEGV), "a read fault on a mapping with missing backing is not delivered while read traps are set");
}
}
void CheckReadTrapThreads() {
::alarm(20);
constexpr std::size_t Threads = 4;
constexpr std::size_t PagesPerThread = 8;
Region region(Threads * PagesPerThread);
char path[] = "/tmp/anyps5-read-trap-XXXXXX";
const int file = ::mkstemp(path);
Require(file >= 0, "cannot create the shared backing");
::unlink(path);
Require(::ftruncate(file, static_cast<off_t>(region.bytes)) == 0, "cannot size the shared backing");
Require(::mmap(region.base, region.bytes, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, file, 0) == region.base, "cannot map the shared backing");
auto* alias = static_cast<std::uint8_t*>(::mmap(nullptr, region.bytes, PROT_READ | PROT_WRITE, MAP_SHARED, file, 0));
Require(alias != MAP_FAILED, "cannot map the second view of the shared backing");
::close(file);
Traps().alias = alias - region.base;
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
static_cast<void>(region.Collect());
Require(GuestWriteWatchSetReadTrapResolver_nid_postfix(&ResolveTrap), "cannot set the read trap resolver");
Traps().fill = 0x5a;
for (std::size_t index = 0; index < Threads * PagesPerThread; ++index)
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(index), region.page), "cannot set a read trap");
std::atomic<bool> start{false};
std::atomic<std::size_t> wrong{0};
std::array<std::thread, Threads> readers;
for (std::size_t thread = 0; thread < Threads; ++thread) {
readers[thread] = std::thread([&, thread] {
while (!start.load()) std::this_thread::yield();
for (std::size_t index = 0; index < Threads * PagesPerThread; ++index) {
const auto page = (index + (thread % 2) * PagesPerThread) % (Threads * PagesPerThread);
if (*reinterpret_cast<const volatile std::uint8_t*>(region.base + page * region.page + thread) != 0x5a) wrong.fetch_add(1);
}
});
}
start.store(true);
for (auto& reader : readers) reader.join();
Require(wrong.load() == 0, "a concurrent read of a trapped page does not see the resolver's bytes");
auto calls = TakeTrapCalls();
std::sort(calls.begin(), calls.end());
Require(calls.size() == Threads * PagesPerThread && std::adjacent_find(calls.begin(), calls.end()) == calls.end(), "concurrent reads do not resolve each trap exactly once");
Traps().alias = 0;
::munmap(alias, region.bytes);
::alarm(0);
}
void CheckReadTrapLateFaults() {
const pid_t child = ::fork();
Require(child >= 0, "cannot fork a child for late read faults");
if (child == 0) {
::alarm(10);
try {
constexpr std::size_t Readers = 32;
Region region(1);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
static_cast<void>(region.Collect());
Require(GuestWriteWatchSetReadTrapResolver_nid_postfix(&ResolveTrap), "cannot set the read trap resolver");
Traps().fill = 0x6b;
Require(GuestWriteWatchTrapReads_nid_postfix(region.Address(0), region.page), "cannot set a read trap");
mach_port_t port = MACH_PORT_NULL;
Require(mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE, &port) == KERN_SUCCESS && mach_port_insert_right(mach_task_self(), port, port, MACH_MSG_TYPE_MAKE_SEND) == KERN_SUCCESS, "cannot create the exception port");
std::atomic<std::size_t> ready{0};
std::atomic<bool> start{false};
std::atomic<std::size_t> wrong{0};
std::array<std::thread, Readers> readers;
for (auto& reader : readers) {
reader = std::thread([&] {
if (thread_set_exception_ports(mach_thread_self(), EXC_MASK_BAD_ACCESS, port, EXCEPTION_DEFAULT, THREAD_STATE_NONE) != KERN_SUCCESS) wrong.fetch_add(1);
ready.fetch_add(1);
while (!start.load()) std::this_thread::yield();
if (*reinterpret_cast<const volatile std::uint8_t*>(region.base) != 0x6b) wrong.fetch_add(1);
});
}
while (ready.load() != Readers) std::this_thread::yield();
start.store(true);
struct Request {
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t thread;
mach_msg_port_descriptor_t task;
NDR_record_t ndr;
exception_type_t exception;
mach_msg_type_number_t codes;
integer_t code[2];
mach_msg_trailer_t trailer;
};
std::vector<Request> held(Readers);
for (auto& request : held) {
Require(mach_msg(&request.header, MACH_RCV_MSG | MACH_RCV_TIMEOUT, 0, sizeof(Request), port, 5000, MACH_PORT_NULL) == MACH_MSG_SUCCESS, "a reader of a trapped page did not fault");
Require(request.exception == EXC_BAD_ACCESS, "a reader of a trapped page raised another exception");
mach_port_deallocate(mach_task_self(), request.thread.name);
mach_port_deallocate(mach_task_self(), request.task.name);
}
Require(*reinterpret_cast<const volatile std::uint8_t*>(region.base) == 0x6b, "a read of a trapped page does not see the resolver's bytes");
Require(PageProtection(region.base) & PROT_READ, "a resolved trap does not give back read access");
for (const auto& request : held) {
struct {
mach_msg_header_t header;
NDR_record_t ndr;
kern_return_t result;
} reply{};
reply.header.msgh_bits = MACH_MSGH_BITS(MACH_MSGH_BITS_REMOTE(request.header.msgh_bits), 0);
reply.header.msgh_remote_port = request.header.msgh_remote_port;
reply.header.msgh_size = sizeof(reply);
reply.header.msgh_id = request.header.msgh_id + 100;
reply.ndr = NDR_record;
reply.result = KERN_FAILURE;
Require(mach_msg(&reply.header, MACH_SEND_MSG, sizeof(reply), 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL) == MACH_MSG_SUCCESS, "cannot pass a held fault on as a signal");
}
for (auto& reader : readers) reader.join();
Require(wrong.load() == 0, "a reader whose fault arrived after its page was given back does not see the resolver's bytes");
Require(TakeTrapCalls().size() == 1, "late read faults resolve the trap again");
} catch (const std::exception& error) {
std::fprintf(stderr, "%s\n", error.what());
::_exit(1);
}
::_exit(0);
}
int status = 0;
Require(::waitpid(child, &status, 0) == child, "cannot wait for the late read fault child");
Require(WIFEXITED(status) && WEXITSTATUS(status) == 0, "32 read faults that arrive after their page was given back are not all retried");
}
void CheckReadTrapFaultBound() {
const pid_t child = ::fork();
Require(child >= 0, "cannot fork a child for persistent read faults");
if (child == 0) {
::alarm(20);
try {
constexpr std::size_t Readers = 66;
constexpr std::size_t Rounds = 40;
const auto bytes = static_cast<std::size_t>(::getpagesize());
Region trapped(1);
GuestWriteWatchRegister_nid_postfix(trapped.base, trapped.bytes);
Require(GuestWriteWatchSetReadTrapResolver_nid_postfix(&ResolveTrap) && GuestWriteWatchTrapReads_nid_postfix(trapped.Address(0), trapped.page), "cannot set a read trap");
char path[] = "/tmp/anyps5-write-watch-XXXXXX";
const int file = ::mkstemp(path);
Require(file >= 0, "cannot create the backing file");
::unlink(path);
Require(::ftruncate(file, static_cast<off_t>(bytes)) == 0, "cannot size the backing file");
auto* mapped = static_cast<std::uint8_t*>(::mmap(nullptr, bytes, PROT_READ | PROT_WRITE, MAP_SHARED, file, 0));
Require(mapped != MAP_FAILED && ::ftruncate(file, 0) == 0, "cannot truncate a watched file mapping");
::close(file);
GuestWriteWatchRegister_nid_postfix(mapped, bytes);
mach_port_t port = MACH_PORT_NULL;
Require(mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE, &port) == KERN_SUCCESS && mach_port_insert_right(mach_task_self(), port, port, MACH_MSG_TYPE_MAKE_SEND) == KERN_SUCCESS, "cannot create the exception port");
std::atomic<std::size_t> ready{0};
std::atomic<bool> start{false};
std::vector<std::thread> readers;
for (std::size_t index = 0; index < Readers; ++index) {
readers.emplace_back([&] {
Require(thread_set_exception_ports(mach_thread_self(), EXC_MASK_BAD_ACCESS, port, EXCEPTION_DEFAULT, THREAD_STATE_NONE) == KERN_SUCCESS, "cannot set a thread exception port");
ready.fetch_add(1);
while (!start.load()) std::this_thread::yield();
static_cast<void>(*reinterpret_cast<const volatile std::uint8_t*>(mapped));
});
}
while (ready.load() != Readers) std::this_thread::yield();
struct Request {
mach_msg_header_t header;
mach_msg_body_t body;
mach_msg_port_descriptor_t thread;
mach_msg_port_descriptor_t task;
NDR_record_t ndr;
exception_type_t exception;
mach_msg_type_number_t codes;
integer_t code[2];
mach_msg_trailer_t trailer;
};
const auto receive = [&](Request& request) {
Require(mach_msg(&request.header, MACH_RCV_MSG | MACH_RCV_TIMEOUT, 0, sizeof(Request), port, 5000, MACH_PORT_NULL) == MACH_MSG_SUCCESS, "a reader of a truncated mapping did not fault");
mach_port_deallocate(mach_task_self(), request.task.name);
};
const auto pass = [](const Request& request) {
struct {
mach_msg_header_t header;
NDR_record_t ndr;
kern_return_t result;
} reply{};
reply.header.msgh_bits = MACH_MSGH_BITS(MACH_MSGH_BITS_REMOTE(request.header.msgh_bits), 0);
reply.header.msgh_remote_port = request.header.msgh_remote_port;
reply.header.msgh_size = sizeof(reply);
reply.header.msgh_id = request.header.msgh_id + 100;
reply.ndr = NDR_record;
reply.result = KERN_FAILURE;
Require(mach_msg(&reply.header, MACH_SEND_MSG, sizeof(reply), 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL) == MACH_MSG_SUCCESS, "cannot pass a held fault on as a signal");
};
start.store(true);
std::vector<Request> held(Readers);
for (auto& request : held) receive(request);
for (std::size_t round = 0; round < Rounds; ++round) {
for (auto& request : held) {
const auto thread = request.thread.name;
pass(request);
receive(request);
Require(request.thread.name == thread, "a held reader faulted out of turn");
mach_port_deallocate(mach_task_self(), thread);
}
}
::_exit(3);
} catch (const std::exception& error) {
std::fprintf(stderr, "%s\n", error.what());
::_exit(1);
}
}
int status = 0;
Require(::waitpid(child, &status, 0) == child, "cannot wait for the persistent read fault child");
Require(WIFSIGNALED(status) && (WTERMSIG(status) == SIGBUS || WTERMSIG(status) == SIGSEGV), "66 threads that keep faulting on a truncated mapping in turn are retried without bound");
}
void CheckRaisedSignals() {
Require(GuestWriteWatchAvailable_nid_postfix(), "write watch is unavailable");
for (const int signal : {SIGBUS, SIGSEGV}) {
const pid_t child = ::fork();
Require(child >= 0, "cannot fork");
if (child == 0) {
::raise(signal);
::_exit(0);
}
int status = 0;
Require(::waitpid(child, &status, 0) == child, "cannot wait for the child");
Require(WIFSIGNALED(status) && WTERMSIG(status) == signal, "a raised fault signal does not terminate the process");
}
}
std::set<std::size_t> Span(std::size_t first, std::size_t last) {
std::set<std::size_t> pages;
for (auto index = first; index <= last; ++index) pages.insert(index);
return pages;
}
void CheckFaultAhead(bool enabled) {
Region region(80);
GuestWriteWatchRegister_nid_postfix(region.base, region.bytes);
static_cast<void>(region.Collect());
const auto write = [&](std::initializer_list<std::size_t> pages, std::uint8_t value) {
for (const auto index : pages) region.base[index * region.page + 5] = value;
};
const auto last = [&](std::size_t first, std::size_t stop) {
if (!enabled) return first;
const auto toBlockEnd = (65536 - region.Address(first) % 65536) / region.page;
return std::min({first + 32, first + std::max<std::size_t>(toBlockEnd, 1), stop}) - 1;
};
write({10, 11}, 1);
Require(region.Collect() == std::set<std::size_t>({10, 11}), "writes to two adjacent pages are not reported exactly");
write({20, 21, 22}, 2);
Require(region.Collect() == Span(20, last(22, 80)), enabled ? "a third sequential write fault does not open the rest of its 64 KiB block" : "with fault-ahead off, sequential writes are not reported exactly");
Require(region.base[20 * region.page + 5] == 2 && region.base[22 * region.page + 5] == 2, "sequential writes were lost");
write({23, 40}, 3);
Require(region.Collect() == std::set<std::size_t>({23, 40}), "writes after a collection are not reported exactly");
write({30}, 4);
write({26, 27, 28}, 4);
auto expected = Span(26, last(28, 30));
expected.insert(30);
Require(region.Collect() == expected, "fault-ahead does not stop at a page that is already writable");
Require(GuestWriteWatchProtect_nid_postfix(region.base + 60 * region.page, region.page, PROT_READ) == 0, "cannot protect a watched page");
static_cast<void>(region.Collect());
write({56, 57, 58}, 5);
Require(region.Collect() == Span(56, last(58, 60)), "fault-ahead does not stop at a read-only page");
if (GuestWriteWatchProtect_nid_postfix(region.base + 66 * region.page, region.page, PROT_READ | PROT_WRITE | PROT_EXEC) == 0) {
static_cast<void>(region.Collect());
write({62, 63, 64}, 7);
Require(region.Collect() == Span(62, last(64, 66)), "fault-ahead does not stop at a writable page with another protection");
Require(KernelProtection(region.base + 66 * region.page) == (PROT_READ | PROT_EXEC), "fault-ahead changed the protection of a page with another one");
region.base[66 * region.page + 5] = 7;
Require(region.Collect() == std::set<std::size_t>({66}), "a write to an executable watched page is not reported");
}
write({77, 78, 79}, 6);
Require(region.Collect() == Span(77, 79), "fault-ahead reaches past the end of a watched range");
Require(region.base[79 * region.page + 5] == 6 && region.base[60 * region.page + 5] == 0, "writes near the range end were lost");
for (std::size_t first = 0; first + 2 < 80; ++first) {
if ((region.Address(first + 3) % 65536) != 0 || first + 3 >= 80) continue;
static_cast<void>(region.Collect());
write({first, first + 1, first + 2}, 8);
Require(region.Collect() == Span(first, first + 2), "fault-ahead crosses into the next 64 KiB block");
break;
}
}
}
int main(int argc, char** argv) {
try {
Require(argc == 2, "expected collect, fresh, armed, register, mapped, host, empty, protection, overlaps, threads, raised, fault-ahead, fault-ahead-off, read-trap, read-trap-threads, read-trap-fault, read-trap-late or read-trap-fault-bound");
const std::string_view mode(argv[1]);
if (mode == "collect") CheckCollect();
else if (mode == "fresh") CheckFresh();
else if (mode == "armed") CheckArmed();
else if (mode == "register") CheckRegisterAgain();
else if (mode == "mapped") CheckRegisterMapped();
else if (mode == "host") CheckHostWrite();
else if (mode == "execute-fault") CheckNonWriteFaults(true);
else if (mode == "read-fault") CheckNonWriteFaults(false);
else if (mode == "empty") CheckEmptyRanges();
else if (mode == "protection") CheckProtection();
else if (mode == "overlaps") CheckOverlaps();
else if (mode == "threads") CheckThreads();
else if (mode == "raised") CheckRaisedSignals();
else if (mode == "fault-ahead") CheckFaultAhead(true);
else if (mode == "fault-ahead-off") CheckFaultAhead(false);
else if (mode == "read-trap") CheckReadTrap();
else if (mode == "read-trap-threads") CheckReadTrapThreads();
else if (mode == "read-trap-fault") CheckReadTrapFaults();
else if (mode == "read-trap-late") CheckReadTrapLateFaults();
else if (mode == "read-trap-fault-bound") CheckReadTrapFaultBound();
else throw std::runtime_error("unknown write watch test");
std::printf("write watch %s passed\n", argv[1]);
return 0;
} catch (const std::exception& error) {
std::fprintf(stderr, "%s\n", error.what());
return 1;
}
}
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