Add support for __builtin_os_log_format[_buffer_size]

These new builtins support a mechanism for logging OS events, using a
printf-like format string to specify the layout of data in a buffer.
The _buffer_size version of the builtin can be used to determine the size
of the buffer to allocate to hold the data, and then __builtin_os_log_format
can write data into that buffer. This implements format checking to report
mismatches between the format string and the data arguments. Most of this
code was written by Chris Willmore.

Differential Revision: https://reviews.llvm.org/D25888

llvm-svn: 284990

1 files changed, 177 insertions, 0 deletions

diff --git a/clang/lib/Analysis/OSLog.cpp b/clang/lib/Analysis/OSLog.cpp
new file mode 100644
index 00000000000..b57e0d1d13f
--- /dev/null
+++ b/clang/lib/Analysis/OSLog.cpp
@@ -0,0 +1,177 @@
+// TODO: header template
+
+#include "clang/Analysis/Analyses/OSLog.h"
+#include "clang/AST/Attr.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/ExprObjC.h"
+#include "clang/Analysis/Analyses/FormatString.h"
+#include "clang/Basic/Builtins.h"
+#include "llvm/ADT/SmallBitVector.h"
+
+using namespace clang;
+using llvm::APInt;
+
+using clang::analyze_os_log::OSLogBufferItem;
+using clang::analyze_os_log::OSLogBufferLayout;
+
+class OSLogFormatStringHandler
+    : public analyze_format_string::FormatStringHandler {
+private:
+  struct ArgData {
+    const Expr *E = nullptr;
+    Optional<OSLogBufferItem::Kind> Kind;
+    Optional<unsigned> Size;
+    unsigned char Flags = 0;
+  };
+  SmallVector<ArgData, 4> ArgsData;
+  ArrayRef<const Expr *> Args;
+
+  OSLogBufferItem::Kind
+  getKind(analyze_format_string::ConversionSpecifier::Kind K) {
+    switch (K) {
+    case clang::analyze_format_string::ConversionSpecifier::sArg: // "%s"
+      return OSLogBufferItem::StringKind;
+    case clang::analyze_format_string::ConversionSpecifier::SArg: // "%S"
+      return OSLogBufferItem::WideStringKind;
+    case clang::analyze_format_string::ConversionSpecifier::PArg: { // "%P"
+      return OSLogBufferItem::PointerKind;
+    case clang::analyze_format_string::ConversionSpecifier::ObjCObjArg: // "%@"
+      return OSLogBufferItem::ObjCObjKind;
+    case clang::analyze_format_string::ConversionSpecifier::PrintErrno: // "%m"
+      return OSLogBufferItem::ErrnoKind;
+    default:
+      return OSLogBufferItem::ScalarKind;
+    }
+    }
+  }
+
+public:
+  OSLogFormatStringHandler(ArrayRef<const Expr *> Args) : Args(Args) {
+    ArgsData.reserve(Args.size());
+  }
+
+  virtual bool HandlePrintfSpecifier(const analyze_printf::PrintfSpecifier &FS,
+                                     const char *StartSpecifier,
+                                     unsigned SpecifierLen) {
+    if (!FS.consumesDataArgument() &&
+        FS.getConversionSpecifier().getKind() !=
+            clang::analyze_format_string::ConversionSpecifier::PrintErrno)
+      return false;
+
+    ArgsData.emplace_back();
+    unsigned ArgIndex = FS.getArgIndex();
+    if (ArgIndex < Args.size())
+      ArgsData.back().E = Args[ArgIndex];
+
+    // First get the Kind
+    ArgsData.back().Kind = getKind(FS.getConversionSpecifier().getKind());
+    if (ArgsData.back().Kind != OSLogBufferItem::ErrnoKind &&
+        !ArgsData.back().E) {
+      // missing argument
+      ArgsData.pop_back();
+      return false;
+    }
+
+    switch (FS.getConversionSpecifier().getKind()) {
+    case clang::analyze_format_string::ConversionSpecifier::sArg:   // "%s"
+    case clang::analyze_format_string::ConversionSpecifier::SArg: { // "%S"
+      auto &precision = FS.getPrecision();
+      switch (precision.getHowSpecified()) {
+      case clang::analyze_format_string::OptionalAmount::NotSpecified: // "%s"
+        break;
+      case clang::analyze_format_string::OptionalAmount::Constant: // "%.16s"
+        ArgsData.back().Size = precision.getConstantAmount();
+        break;
+      case clang::analyze_format_string::OptionalAmount::Arg: // "%.*s"
+        ArgsData.back().Kind = OSLogBufferItem::CountKind;
+        break;
+      case clang::analyze_format_string::OptionalAmount::Invalid:
+        return false;
+      }
+      break;
+    }
+    case clang::analyze_format_string::ConversionSpecifier::PArg: { // "%P"
+      auto &precision = FS.getPrecision();
+      switch (precision.getHowSpecified()) {
+      case clang::analyze_format_string::OptionalAmount::NotSpecified: // "%P"
+        return false; // length must be supplied with pointer format specifier
+      case clang::analyze_format_string::OptionalAmount::Constant: // "%.16P"
+        ArgsData.back().Size = precision.getConstantAmount();
+        break;
+      case clang::analyze_format_string::OptionalAmount::Arg: // "%.*P"
+        ArgsData.back().Kind = OSLogBufferItem::CountKind;
+        break;
+      case clang::analyze_format_string::OptionalAmount::Invalid:
+        return false;
+      }
+      break;
+    }
+    default:
+      break;
+    }
+
+    if (FS.isPrivate()) {
+      ArgsData.back().Flags |= OSLogBufferItem::IsPrivate;
+    }
+    if (FS.isPublic()) {
+      ArgsData.back().Flags |= OSLogBufferItem::IsPublic;
+    }
+    return true;
+  }
+
+  void computeLayout(ASTContext &Ctx, OSLogBufferLayout &Layout) const {
+    Layout.Items.clear();
+    for (auto &Data : ArgsData) {
+      if (Data.Size)
+        Layout.Items.emplace_back(Ctx, CharUnits::fromQuantity(*Data.Size),
+                                  Data.Flags);
+      if (Data.Kind) {
+        CharUnits Size;
+        if (*Data.Kind == OSLogBufferItem::ErrnoKind)
+          Size = CharUnits::Zero();
+        else
+          Size = Ctx.getTypeSizeInChars(Data.E->getType());
+        Layout.Items.emplace_back(*Data.Kind, Data.E, Size, Data.Flags);
+      } else {
+        auto Size = Ctx.getTypeSizeInChars(Data.E->getType());
+        Layout.Items.emplace_back(OSLogBufferItem::ScalarKind, Data.E, Size,
+                                  Data.Flags);
+      }
+    }
+  }
+};
+
+bool clang::analyze_os_log::computeOSLogBufferLayout(
+    ASTContext &Ctx, const CallExpr *E, OSLogBufferLayout &Layout) {
+  ArrayRef<const Expr *> Args(E->getArgs(), E->getArgs() + E->getNumArgs());
+
+  const Expr *StringArg;
+  ArrayRef<const Expr *> VarArgs;
+  switch (E->getBuiltinCallee()) {
+  case Builtin::BI__builtin_os_log_format_buffer_size:
+    assert(E->getNumArgs() >= 1 &&
+           "__builtin_os_log_format_buffer_size takes at least 1 argument");
+    StringArg = E->getArg(0);
+    VarArgs = Args.slice(1);
+    break;
+  case Builtin::BI__builtin_os_log_format:
+    assert(E->getNumArgs() >= 2 &&
+           "__builtin_os_log_format takes at least 2 arguments");
+    StringArg = E->getArg(1);
+    VarArgs = Args.slice(2);
+    break;
+  default:
+    llvm_unreachable("non-os_log builtin passed to computeOSLogBufferLayout");
+  }
+
+  const StringLiteral *Lit = cast<StringLiteral>(StringArg->IgnoreParenCasts());
+  assert(Lit && (Lit->isAscii() || Lit->isUTF8()));
+  StringRef Data = Lit->getString();
+  OSLogFormatStringHandler H(VarArgs);
+  ParsePrintfString(H, Data.begin(), Data.end(), Ctx.getLangOpts(),
+                    Ctx.getTargetInfo(), /*isFreeBSDKPrintf*/ false);
+
+  H.computeLayout(Ctx, Layout);
+  return true;
+}