| //===--- SignalHandlerCheck.cpp - clang-tidy ------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "SignalHandlerCheck.h" |
| #include "clang/ASTMatchers/ASTMatchFinder.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/STLExtras.h" |
| |
| // This is the minimal set of safe functions. |
| // https://wiki.sei.cmu.edu/confluence/display/c/SIG30-C.+Call+only+asynchronous-safe+functions+within+signal+handlers |
| constexpr llvm::StringLiteral MinimalConformingFunctions[] = { |
| "signal", "abort", "_Exit", "quick_exit"}; |
| |
| // The POSIX-defined set of safe functions. |
| // https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 |
| // 'quick_exit' is added to the set additionally because it looks like the |
| // mentioned POSIX specification was not updated after 'quick_exit' appeared |
| // in the C11 standard. |
| // Also, we want to keep the "minimal set" a subset of the "POSIX set". |
| // The list is repeated in bugprone-signal-handler.rst and should be kept up to date. |
| constexpr llvm::StringLiteral POSIXConformingFunctions[] = { |
| "_Exit", |
| "_exit", |
| "abort", |
| "accept", |
| "access", |
| "aio_error", |
| "aio_return", |
| "aio_suspend", |
| "alarm", |
| "bind", |
| "cfgetispeed", |
| "cfgetospeed", |
| "cfsetispeed", |
| "cfsetospeed", |
| "chdir", |
| "chmod", |
| "chown", |
| "clock_gettime", |
| "close", |
| "connect", |
| "creat", |
| "dup", |
| "dup2", |
| "execl", |
| "execle", |
| "execv", |
| "execve", |
| "faccessat", |
| "fchdir", |
| "fchmod", |
| "fchmodat", |
| "fchown", |
| "fchownat", |
| "fcntl", |
| "fdatasync", |
| "fexecve", |
| "ffs", |
| "fork", |
| "fstat", |
| "fstatat", |
| "fsync", |
| "ftruncate", |
| "futimens", |
| "getegid", |
| "geteuid", |
| "getgid", |
| "getgroups", |
| "getpeername", |
| "getpgrp", |
| "getpid", |
| "getppid", |
| "getsockname", |
| "getsockopt", |
| "getuid", |
| "htonl", |
| "htons", |
| "kill", |
| "link", |
| "linkat", |
| "listen", |
| "longjmp", |
| "lseek", |
| "lstat", |
| "memccpy", |
| "memchr", |
| "memcmp", |
| "memcpy", |
| "memmove", |
| "memset", |
| "mkdir", |
| "mkdirat", |
| "mkfifo", |
| "mkfifoat", |
| "mknod", |
| "mknodat", |
| "ntohl", |
| "ntohs", |
| "open", |
| "openat", |
| "pause", |
| "pipe", |
| "poll", |
| "posix_trace_event", |
| "pselect", |
| "pthread_kill", |
| "pthread_self", |
| "pthread_sigmask", |
| "quick_exit", |
| "raise", |
| "read", |
| "readlink", |
| "readlinkat", |
| "recv", |
| "recvfrom", |
| "recvmsg", |
| "rename", |
| "renameat", |
| "rmdir", |
| "select", |
| "sem_post", |
| "send", |
| "sendmsg", |
| "sendto", |
| "setgid", |
| "setpgid", |
| "setsid", |
| "setsockopt", |
| "setuid", |
| "shutdown", |
| "sigaction", |
| "sigaddset", |
| "sigdelset", |
| "sigemptyset", |
| "sigfillset", |
| "sigismember", |
| "siglongjmp", |
| "signal", |
| "sigpause", |
| "sigpending", |
| "sigprocmask", |
| "sigqueue", |
| "sigset", |
| "sigsuspend", |
| "sleep", |
| "sockatmark", |
| "socket", |
| "socketpair", |
| "stat", |
| "stpcpy", |
| "stpncpy", |
| "strcat", |
| "strchr", |
| "strcmp", |
| "strcpy", |
| "strcspn", |
| "strlen", |
| "strncat", |
| "strncmp", |
| "strncpy", |
| "strnlen", |
| "strpbrk", |
| "strrchr", |
| "strspn", |
| "strstr", |
| "strtok_r", |
| "symlink", |
| "symlinkat", |
| "tcdrain", |
| "tcflow", |
| "tcflush", |
| "tcgetattr", |
| "tcgetpgrp", |
| "tcsendbreak", |
| "tcsetattr", |
| "tcsetpgrp", |
| "time", |
| "timer_getoverrun", |
| "timer_gettime", |
| "timer_settime", |
| "times", |
| "umask", |
| "uname", |
| "unlink", |
| "unlinkat", |
| "utime", |
| "utimensat", |
| "utimes", |
| "wait", |
| "waitpid", |
| "wcpcpy", |
| "wcpncpy", |
| "wcscat", |
| "wcschr", |
| "wcscmp", |
| "wcscpy", |
| "wcscspn", |
| "wcslen", |
| "wcsncat", |
| "wcsncmp", |
| "wcsncpy", |
| "wcsnlen", |
| "wcspbrk", |
| "wcsrchr", |
| "wcsspn", |
| "wcsstr", |
| "wcstok", |
| "wmemchr", |
| "wmemcmp", |
| "wmemcpy", |
| "wmemmove", |
| "wmemset", |
| "write"}; |
| |
| using namespace clang::ast_matchers; |
| |
| namespace clang::tidy { |
| |
| template <> |
| struct OptionEnumMapping< |
| bugprone::SignalHandlerCheck::AsyncSafeFunctionSetKind> { |
| static llvm::ArrayRef<std::pair< |
| bugprone::SignalHandlerCheck::AsyncSafeFunctionSetKind, StringRef>> |
| getEnumMapping() { |
| static constexpr std::pair< |
| bugprone::SignalHandlerCheck::AsyncSafeFunctionSetKind, StringRef> |
| Mapping[] = { |
| {bugprone::SignalHandlerCheck::AsyncSafeFunctionSetKind::Minimal, |
| "minimal"}, |
| {bugprone::SignalHandlerCheck::AsyncSafeFunctionSetKind::POSIX, |
| "POSIX"}, |
| }; |
| return ArrayRef(Mapping); |
| } |
| }; |
| |
| namespace bugprone { |
| |
| namespace { |
| |
| /// Returns if a function is declared inside a system header. |
| /// These functions are considered to be "standard" (system-provided) library |
| /// functions. |
| bool isStandardFunction(const FunctionDecl *FD) { |
| // Find a possible redeclaration in system header. |
| // FIXME: Looking at the canonical declaration is not the most exact way |
| // to do this. |
| |
| // Most common case will be inclusion directly from a header. |
| // This works fine by using canonical declaration. |
| // a.c |
| // #include <sysheader.h> |
| |
| // Next most common case will be extern declaration. |
| // Can't catch this with either approach. |
| // b.c |
| // extern void sysfunc(void); |
| |
| // Canonical declaration is the first found declaration, so this works. |
| // c.c |
| // #include <sysheader.h> |
| // extern void sysfunc(void); // redecl won't matter |
| |
| // This does not work with canonical declaration. |
| // Probably this is not a frequently used case but may happen (the first |
| // declaration can be in a non-system header for example). |
| // d.c |
| // extern void sysfunc(void); // Canonical declaration, not in system header. |
| // #include <sysheader.h> |
| |
| return FD->getASTContext().getSourceManager().isInSystemHeader( |
| FD->getCanonicalDecl()->getLocation()); |
| } |
| |
| /// Check if a statement is "C++-only". |
| /// This includes all statements that have a class name with "CXX" prefix |
| /// and every other statement that is declared in file ExprCXX.h. |
| bool isCXXOnlyStmt(const Stmt *S) { |
| StringRef Name = S->getStmtClassName(); |
| if (Name.startswith("CXX")) |
| return true; |
| // Check for all other class names in ExprCXX.h that have no 'CXX' prefix. |
| return isa<ArrayTypeTraitExpr, BuiltinBitCastExpr, CUDAKernelCallExpr, |
| CoawaitExpr, CoreturnStmt, CoroutineBodyStmt, CoroutineSuspendExpr, |
| CoyieldExpr, DependentCoawaitExpr, DependentScopeDeclRefExpr, |
| ExprWithCleanups, ExpressionTraitExpr, FunctionParmPackExpr, |
| LambdaExpr, MSDependentExistsStmt, MSPropertyRefExpr, |
| MSPropertySubscriptExpr, MaterializeTemporaryExpr, OverloadExpr, |
| PackExpansionExpr, SizeOfPackExpr, SubstNonTypeTemplateParmExpr, |
| SubstNonTypeTemplateParmPackExpr, TypeTraitExpr, |
| UserDefinedLiteral>(S); |
| } |
| |
| /// Given a call graph node of a \p Caller function and a \p Callee that is |
| /// called from \p Caller, get a \c CallExpr of the corresponding function call. |
| /// It is unspecified which call is found if multiple calls exist, but the order |
| /// should be deterministic (depend only on the AST). |
| Expr *findCallExpr(const CallGraphNode *Caller, const CallGraphNode *Callee) { |
| auto FoundCallee = llvm::find_if( |
| Caller->callees(), [Callee](const CallGraphNode::CallRecord &Call) { |
| return Call.Callee == Callee; |
| }); |
| assert(FoundCallee != Caller->end() && |
| "Callee should be called from the caller function here."); |
| return FoundCallee->CallExpr; |
| } |
| |
| SourceRange getSourceRangeOfStmt(const Stmt *S, ASTContext &Ctx) { |
| ParentMapContext &PM = Ctx.getParentMapContext(); |
| DynTypedNode P = DynTypedNode::create(*S); |
| while (P.getSourceRange().isInvalid()) { |
| DynTypedNodeList PL = PM.getParents(P); |
| if (PL.size() != 1) |
| return {}; |
| P = PL[0]; |
| } |
| return P.getSourceRange(); |
| } |
| |
| } // namespace |
| |
| AST_MATCHER(FunctionDecl, isStandardFunction) { |
| return isStandardFunction(&Node); |
| } |
| |
| SignalHandlerCheck::SignalHandlerCheck(StringRef Name, |
| ClangTidyContext *Context) |
| : ClangTidyCheck(Name, Context), |
| AsyncSafeFunctionSet(Options.get("AsyncSafeFunctionSet", |
| AsyncSafeFunctionSetKind::POSIX)) { |
| if (AsyncSafeFunctionSet == AsyncSafeFunctionSetKind::Minimal) { |
| for (StringRef v : MinimalConformingFunctions) |
| ConformingFunctions.insert(v); |
| } else { |
| for (StringRef v : POSIXConformingFunctions) |
| ConformingFunctions.insert(v); |
| } |
| } |
| |
| void SignalHandlerCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) { |
| Options.store(Opts, "AsyncSafeFunctionSet", AsyncSafeFunctionSet); |
| } |
| |
| bool SignalHandlerCheck::isLanguageVersionSupported( |
| const LangOptions &LangOpts) const { |
| return !LangOpts.CPlusPlus17; |
| } |
| |
| void SignalHandlerCheck::registerMatchers(MatchFinder *Finder) { |
| auto SignalFunction = functionDecl(hasAnyName("::signal", "::std::signal"), |
| parameterCountIs(2), isStandardFunction()); |
| auto HandlerExpr = |
| declRefExpr(hasDeclaration(functionDecl().bind("handler_decl")), |
| unless(isExpandedFromMacro("SIG_IGN")), |
| unless(isExpandedFromMacro("SIG_DFL"))) |
| .bind("handler_expr"); |
| auto HandlerLambda = cxxMemberCallExpr( |
| on(expr(ignoringParenImpCasts(lambdaExpr().bind("handler_lambda"))))); |
| Finder->addMatcher(callExpr(callee(SignalFunction), |
| hasArgument(1, anyOf(HandlerExpr, HandlerLambda))) |
| .bind("register_call"), |
| this); |
| } |
| |
| void SignalHandlerCheck::check(const MatchFinder::MatchResult &Result) { |
| if (const auto *HandlerLambda = |
| Result.Nodes.getNodeAs<LambdaExpr>("handler_lambda")) { |
| diag(HandlerLambda->getBeginLoc(), |
| "lambda function is not allowed as signal handler (until C++17)") |
| << HandlerLambda->getSourceRange(); |
| return; |
| } |
| |
| const auto *HandlerDecl = |
| Result.Nodes.getNodeAs<FunctionDecl>("handler_decl"); |
| const auto *HandlerExpr = Result.Nodes.getNodeAs<DeclRefExpr>("handler_expr"); |
| assert(Result.Nodes.getNodeAs<CallExpr>("register_call") && HandlerDecl && |
| HandlerExpr && "All of these should exist in a match here."); |
| |
| if (CG.size() <= 1) { |
| // Call graph must be populated with the entire TU at the beginning. |
| // (It is possible to add a single function but the functions called from it |
| // are not analysed in this case.) |
| CG.addToCallGraph(const_cast<TranslationUnitDecl *>( |
| HandlerDecl->getTranslationUnitDecl())); |
| assert(CG.size() > 1 && |
| "There should be at least one function added to call graph."); |
| } |
| |
| if (!HandlerDecl->hasBody()) { |
| // Check the handler function. |
| // The warning is placed to the signal handler registration. |
| // No need to display a call chain and no need for more checks. |
| (void)checkFunction(HandlerDecl, HandlerExpr, {}); |
| return; |
| } |
| |
| // FIXME: Update CallGraph::getNode to use canonical decl? |
| CallGraphNode *HandlerNode = CG.getNode(HandlerDecl->getCanonicalDecl()); |
| assert(HandlerNode && |
| "Handler with body should be present in the call graph."); |
| // Start from signal handler and visit every function call. |
| auto Itr = llvm::df_begin(HandlerNode), ItrE = llvm::df_end(HandlerNode); |
| while (Itr != ItrE) { |
| const auto *CallF = dyn_cast<FunctionDecl>((*Itr)->getDecl()); |
| unsigned int PathL = Itr.getPathLength(); |
| if (CallF) { |
| // A signal handler or a function transitively reachable from the signal |
| // handler was found to be unsafe. |
| // Generate notes for the whole call chain (including the signal handler |
| // registration). |
| const Expr *CallOrRef = (PathL > 1) |
| ? findCallExpr(Itr.getPath(PathL - 2), *Itr) |
| : HandlerExpr; |
| auto ChainReporter = [this, &Itr, HandlerExpr](bool SkipPathEnd) { |
| reportHandlerChain(Itr, HandlerExpr, SkipPathEnd); |
| }; |
| // If problems were found in a function (`CallF`), skip the analysis of |
| // functions that are called from it. |
| if (checkFunction(CallF, CallOrRef, ChainReporter)) |
| Itr.skipChildren(); |
| else |
| ++Itr; |
| } else { |
| ++Itr; |
| } |
| } |
| } |
| |
| bool SignalHandlerCheck::checkFunction( |
| const FunctionDecl *FD, const Expr *CallOrRef, |
| std::function<void(bool)> ChainReporter) { |
| bool FunctionIsCalled = isa<CallExpr>(CallOrRef); |
| |
| if (isStandardFunction(FD)) { |
| if (!isStandardFunctionAsyncSafe(FD)) { |
| diag(CallOrRef->getBeginLoc(), "standard function %0 may not be " |
| "asynchronous-safe; " |
| "%select{using it as|calling it from}1 " |
| "a signal handler may be dangerous") |
| << FD << FunctionIsCalled << CallOrRef->getSourceRange(); |
| if (ChainReporter) |
| ChainReporter(/*SkipPathEnd=*/true); |
| return true; |
| } |
| return false; |
| } |
| |
| if (!FD->hasBody()) { |
| diag(CallOrRef->getBeginLoc(), "cannot verify that external function %0 is " |
| "asynchronous-safe; " |
| "%select{using it as|calling it from}1 " |
| "a signal handler may be dangerous") |
| << FD << FunctionIsCalled << CallOrRef->getSourceRange(); |
| if (ChainReporter) |
| ChainReporter(/*SkipPathEnd=*/true); |
| return true; |
| } |
| |
| if (getLangOpts().CPlusPlus) |
| return checkFunctionCPP14(FD, CallOrRef, ChainReporter); |
| |
| return false; |
| } |
| |
| bool SignalHandlerCheck::checkFunctionCPP14( |
| const FunctionDecl *FD, const Expr *CallOrRef, |
| std::function<void(bool)> ChainReporter) { |
| if (!FD->isExternC()) { |
| diag(CallOrRef->getBeginLoc(), |
| "functions without C linkage are not allowed as signal " |
| "handler (until C++17)"); |
| if (ChainReporter) |
| ChainReporter(/*SkipPathEnd=*/true); |
| return true; |
| } |
| |
| const FunctionDecl *FBody; |
| const Stmt *BodyS = FD->getBody(FBody); |
| if (!BodyS) |
| return false; |
| |
| bool StmtProblemsFound = false; |
| ASTContext &Ctx = FBody->getASTContext(); |
| auto Matches = |
| match(decl(forEachDescendant(stmt().bind("stmt"))), *FBody, Ctx); |
| for (const auto &Match : Matches) { |
| const auto *FoundS = Match.getNodeAs<Stmt>("stmt"); |
| if (isCXXOnlyStmt(FoundS)) { |
| SourceRange R = getSourceRangeOfStmt(FoundS, Ctx); |
| if (R.isInvalid()) |
| continue; |
| diag(R.getBegin(), |
| "C++-only construct is not allowed in signal handler (until C++17)") |
| << R; |
| diag(R.getBegin(), "internally, the statement is parsed as a '%0'", |
| DiagnosticIDs::Remark) |
| << FoundS->getStmtClassName(); |
| if (ChainReporter) |
| ChainReporter(/*SkipPathEnd=*/false); |
| StmtProblemsFound = true; |
| } |
| } |
| |
| return StmtProblemsFound; |
| } |
| |
| bool SignalHandlerCheck::isStandardFunctionAsyncSafe( |
| const FunctionDecl *FD) const { |
| assert(isStandardFunction(FD)); |
| |
| const IdentifierInfo *II = FD->getIdentifier(); |
| // Unnamed functions are not explicitly allowed. |
| // C++ std operators may be unsafe and not within the |
| // "common subset of C and C++". |
| if (!II) |
| return false; |
| |
| if (!FD->isInStdNamespace() && !FD->isGlobal()) |
| return false; |
| |
| if (ConformingFunctions.count(II->getName())) |
| return true; |
| |
| return false; |
| } |
| |
| void SignalHandlerCheck::reportHandlerChain( |
| const llvm::df_iterator<clang::CallGraphNode *> &Itr, |
| const DeclRefExpr *HandlerRef, bool SkipPathEnd) { |
| int CallLevel = Itr.getPathLength() - 2; |
| assert(CallLevel >= -1 && "Empty iterator?"); |
| |
| const CallGraphNode *Caller = Itr.getPath(CallLevel + 1), *Callee = nullptr; |
| while (CallLevel >= 0) { |
| Callee = Caller; |
| Caller = Itr.getPath(CallLevel); |
| const Expr *CE = findCallExpr(Caller, Callee); |
| if (SkipPathEnd) |
| SkipPathEnd = false; |
| else |
| diag(CE->getBeginLoc(), "function %0 called here from %1", |
| DiagnosticIDs::Note) |
| << cast<FunctionDecl>(Callee->getDecl()) |
| << cast<FunctionDecl>(Caller->getDecl()); |
| --CallLevel; |
| } |
| |
| if (!SkipPathEnd) |
| diag(HandlerRef->getBeginLoc(), |
| "function %0 registered here as signal handler", DiagnosticIDs::Note) |
| << cast<FunctionDecl>(Caller->getDecl()) |
| << HandlerRef->getSourceRange(); |
| } |
| |
| } // namespace bugprone |
| } // namespace clang::tidy |
