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Use MREMAP_DONTUNMAP to avoid race if possible

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This commit is contained in:
LoveSy 2025-03-19 01:02:35 +08:00
parent cef80a97a7
commit 02c1730a64
1 changed files with 27 additions and 24 deletions
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51
lsplt/src/main/jni/lsplt.cc
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@ -18,7 +18,8 @@ namespace {
const uintptr_t kPageSize = getpagesize();
inline auto PageStart(uintptr_t addr) {
return reinterpret_cast<char *>(addr / kPageSize * kPageSize); }
return reinterpret_cast<char *>(addr / kPageSize * kPageSize);
}
inline auto PageEnd(uintptr_t addr) {
return reinterpret_cast<char *>(reinterpret_cast<uintptr_t>(PageStart(addr)) + kPageSize);
@ -72,7 +73,7 @@ public:
continue;
}
auto start = map.start;
bool self = map.inode == kSelfInode && map.dev == kSelfDev;
const bool self = map.inode == kSelfInode && map.dev == kSelfDev;
info.emplace(start, HookInfo{{std::move(map)}, {}, 0, nullptr, self});
}
return info;
@ -127,10 +128,16 @@ public:
auto *backup_addr = sys_mmap(nullptr, len, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
LOGD("Backup %p to %p", reinterpret_cast<void *>(addr), backup_addr);
if (backup_addr == MAP_FAILED) return false;
if (auto *new_addr = sys_mremap(reinterpret_cast<void *>(info.start), len, len,
MREMAP_FIXED | MREMAP_MAYMOVE, backup_addr);
if (auto *new_addr =
sys_mremap(reinterpret_cast<void *>(info.start), len, len,
MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP, backup_addr);
new_addr == MAP_FAILED || new_addr != backup_addr) {
return false;
new_addr = sys_mremap(reinterpret_cast<void *>(info.start), len, len,
MREMAP_FIXED | MREMAP_MAYMOVE, backup_addr);
if (new_addr == MAP_FAILED || new_addr != backup_addr) {
return false;
}
LOGD("Backup with MREMAP_DONTUNMAP failed, tried without it");
}
if (auto *new_addr = sys_mmap(reinterpret_cast<void *>(info.start), len,
PROT_READ | PROT_WRITE | info.perms,
@ -168,7 +175,8 @@ public:
LOGD("Restore %p from %p", reinterpret_cast<void *>(info.start),
reinterpret_cast<void *>(info.backup));
// Note that we have to always use sys_mremap here,
// see https://cs.android.com/android/_/android/platform/bionic/+/4200e260d266fd0c176e71fbd720d0bab04b02db
// see
// https://cs.android.com/android/_/android/platform/bionic/+/4200e260d266fd0c176e71fbd720d0bab04b02db
if (auto *new_addr =
sys_mremap(reinterpret_cast<void *>(info.backup), len, len,
MREMAP_FIXED | MREMAP_MAYMOVE, reinterpret_cast<void *>(info.start));
@ -240,8 +248,7 @@ std::list<RegisterInfo> register_info;
HookInfos hook_info;
} // namespace
namespace lsplt {
inline namespace v2 {
namespace lsplt::inline v2 {
[[maybe_unused]] std::vector<MapInfo> MapInfo::Scan(std::string_view pid) {
constexpr static auto kPermLength = 5;
constexpr static auto kMapEntry = 7;
@ -268,9 +275,9 @@ inline namespace v2 {
continue;
}
while (path_off < read && isspace(line[path_off])) path_off++;
auto &ref = info.emplace_back(MapInfo{start, end, 0, perm[3] == 'p', off,
static_cast<dev_t>(makedev(dev_major, dev_minor)),
inode, line + path_off});
auto &ref = info.emplace_back(start, end, 0, perm[3] == 'p', off,
static_cast<dev_t>(makedev(dev_major, dev_minor)), inode,
line + path_off);
if (perm[0] == 'r') ref.perms |= PROT_READ;
if (perm[1] == 'w') ref.perms |= PROT_WRITE;
if (perm[2] == 'x') ref.perms |= PROT_EXEC;
@ -284,16 +291,13 @@ inline namespace v2 {
void **backup) {
if (dev == 0 || inode == 0 || symbol.empty() || !callback) return false;
std::unique_lock lock(hook_mutex);
const std::unique_lock lock(hook_mutex);
static_assert(std::numeric_limits<uintptr_t>::min() == 0);
static_assert(std::numeric_limits<uintptr_t>::max() == -1);
[[maybe_unused]] const auto &info = register_info.emplace_back(
RegisterInfo{dev,
inode,
{std::numeric_limits<uintptr_t>::min(), std::numeric_limits<uintptr_t>::max()},
std::string{symbol},
callback,
backup});
dev, inode,
std::pair{std::numeric_limits<uintptr_t>::min(), std::numeric_limits<uintptr_t>::max()},
std::string{symbol}, callback, backup);
LOGV("RegisterHook %lu %s", info.inode, info.symbol.data());
return true;
@ -303,11 +307,11 @@ inline namespace v2 {
std::string_view symbol, void *callback, void **backup) {
if (dev == 0 || inode == 0 || symbol.empty() || !callback) return false;
std::unique_lock lock(hook_mutex);
const std::unique_lock lock(hook_mutex);
static_assert(std::numeric_limits<uintptr_t>::min() == 0);
static_assert(std::numeric_limits<uintptr_t>::max() == -1);
[[maybe_unused]] const auto &info = register_info.emplace_back(
RegisterInfo{dev, inode, {offset, offset + size}, std::string{symbol}, callback, backup});
dev, inode, std::pair{offset, offset + size}, std::string{symbol}, callback, backup);
LOGV("RegisterHook %lu %" PRIxPTR "-%" PRIxPTR " %s", info.inode, info.offset_range.first,
info.offset_range.second, info.symbol.data());
@ -315,7 +319,7 @@ inline namespace v2 {
}
[[maybe_unused]] bool CommitHook() {
std::unique_lock lock(hook_mutex);
const std::unique_lock lock(hook_mutex);
if (register_info.empty()) return true;
auto new_hook_info = HookInfos::ScanHookInfo();
@ -331,8 +335,7 @@ inline namespace v2 {
}
[[gnu::destructor]] [[maybe_unused]] bool InvalidateBackup() {
std::unique_lock lock(hook_mutex);
const std::unique_lock lock(hook_mutex);
return hook_info.InvalidateBackup();
}
} // namespace v2
} // namespace lsplt
} // namespace lsplt::inline v2