GsymCreator.h

Go to the documentation of this file.

//===- GsymCreator.h --------------------------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H
#define LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H
 
#include <functional>
#include <memory>
#include <mutex>
#include <thread>
 
#include "llvm/ADT/AddressRanges.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/DebugInfo/GSYM/FileEntry.h"
#include "llvm/DebugInfo/GSYM/FunctionInfo.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Path.h"
 
namespace llvm {
 
namespace gsym {
class FileWriter;
 
/// GsymCreator is used to emit GSYM data to a stand alone file or section
/// within a file.
///
/// The GsymCreator is designed to be used in 3 stages:
/// - Create FunctionInfo objects and add them
/// - Finalize the GsymCreator object
/// - Save to file or section
///
/// The first stage involves creating FunctionInfo objects from another source
/// of information like compiler debug info metadata, DWARF or Breakpad files.
/// Any strings in the FunctionInfo or contained information, like InlineInfo
/// or LineTable objects, should get the string table offsets by calling
/// GsymCreator::insertString(...). Any file indexes that are needed should be
/// obtained by calling GsymCreator::insertFile(...). All of the function calls
/// in GsymCreator are thread safe. This allows multiple threads to create and
/// add FunctionInfo objects while parsing debug information.
///
/// Once all of the FunctionInfo objects have been added, the
/// GsymCreator::finalize(...) must be called prior to saving. This function
/// will sort the FunctionInfo objects, finalize the string table, and do any
/// other passes on the information needed to prepare the information to be
/// saved.
///
/// Once the object has been finalized, it can be saved to a file or section.
///
/// ENCODING
///
/// GSYM files are designed to be memory mapped into a process as shared, read
/// only data, and used as is.
///
/// The GSYM file format when in a stand alone file consists of:
///   - Header
///   - Address Table
///   - Function Info Offsets
///   - File Table
///   - String Table
///   - Function Info Data
///
/// HEADER
///
/// The header is fully described in "llvm/DebugInfo/GSYM/Header.h".
///
/// ADDRESS TABLE
///
/// The address table immediately follows the header in the file and consists
/// of Header.NumAddresses address offsets. These offsets are sorted and can be
/// binary searched for efficient lookups. Addresses in the address table are
/// stored as offsets from a 64 bit base address found in Header.BaseAddress.
/// This allows the address table to contain 8, 16, or 32 offsets. This allows
/// the address table to not require full 64 bit addresses for each address.
/// The resulting GSYM size is smaller and causes fewer pages to be touched
/// during address lookups when the address table is smaller. The size of the
/// address offsets in the address table is specified in the header in
/// Header.AddrOffSize. The first offset in the address table is aligned to
/// Header.AddrOffSize alignment to ensure efficient access when loaded into
/// memory.
///
/// FUNCTION INFO OFFSETS TABLE
///
/// The function info offsets table immediately follows the address table and
/// consists of Header.NumAddresses 32 bit file offsets: one for each address
/// in the address table. This data is aligned to a 4 byte boundary. The
/// offsets in this table are the relative offsets from the start offset of the
/// GSYM header and point to the function info data for each address in the
/// address table. Keeping this data separate from the address table helps to
/// reduce the number of pages that are touched when address lookups occur on a
/// GSYM file.
///
/// FILE TABLE
///
/// The file table immediately follows the function info offsets table. The
/// encoding of the FileTable is:
///
/// struct FileTable {
///   uint32_t Count;
///   FileEntry Files[];
/// };
///
/// The file table starts with a 32 bit count of the number of files that are
/// used in all of the function info, followed by that number of FileEntry
/// structures. The file table is aligned to a 4 byte boundary, Each file in
/// the file table is represented with a FileEntry structure.
/// See "llvm/DebugInfo/GSYM/FileEntry.h" for details.
///
/// STRING TABLE
///
/// The string table follows the file table in stand alone GSYM files and
/// contains all strings for everything contained in the GSYM file. Any string
/// data should be added to the string table and any references to strings
/// inside GSYM information must be stored as 32 bit string table offsets into
/// this string table. The string table always starts with an empty string at
/// offset zero and is followed by any strings needed by the GSYM information.
/// The start of the string table is not aligned to any boundary.
///
/// FUNCTION INFO DATA
///
/// The function info data is the payload that contains information about the
/// address that is being looked up. It contains all of the encoded
/// FunctionInfo objects. Each encoded FunctionInfo's data is pointed to by an
/// entry in the Function Info Offsets Table. For details on the exact encoding
/// of FunctionInfo objects, see "llvm/DebugInfo/GSYM/FunctionInfo.h".
class GsymCreator {
  // Private member variables require Mutex protections
  mutable std::mutex Mutex;
  std::vector<FunctionInfo> Funcs;
  StringTableBuilder StrTab;
  StringSet<> StringStorage;
  DenseMap<llvm::gsym::FileEntry, uint32_t> FileEntryToIndex;
  // Needed for mapping string offsets back to the string stored in \a StrTab.
  DenseMap<uint64_t, CachedHashStringRef> StringOffsetMap;
  std::vector<llvm::gsym::FileEntry> Files;
  std::vector<uint8_t> UUID;
  std::optional<AddressRanges> ValidTextRanges;
  AddressRanges Ranges;
  std::optional<uint64_t> BaseAddress;
  bool Finalized = false;
  bool Quiet;
 
 
  /// Get the first function start address.
  ///
  /// \returns The start address of the first FunctionInfo or std::nullopt if
  /// there are no function infos.
  std::optional<uint64_t> getFirstFunctionAddress() const;
 
  /// Get the last function address.
  ///
  /// \returns The start address of the last FunctionInfo or std::nullopt if
  /// there are no function infos.
  std::optional<uint64_t> getLastFunctionAddress() const;
 
  /// Get the base address to use for this GSYM file.
  ///
  /// \returns The base address to put into the header and to use when creating
  ///          the address offset table or std::nullpt if there are no valid
  ///          function infos or if the base address wasn't specified.
  std::optional<uint64_t> getBaseAddress() const;
 
  /// Get the size of an address offset in the address offset table.
  ///
  /// GSYM files store offsets from the base address in the address offset table
  /// and we store the size of the address offsets in the GSYM header. This
  /// function will calculate the size in bytes of these address offsets based
  /// on the current contents of the GSYM file.
  ///
  /// \returns The size in byets of the address offsets.
  uint8_t getAddressOffsetSize() const;
 
  /// Get the maximum address offset for the current address offset size.
  ///
  /// This is used when creating the address offset table to ensure we have
  /// values that are in range so we don't end up truncating address offsets
  /// when creating GSYM files as the code evolves.
  ///
  /// \returns The maximum address offset value that will be encoded into a GSYM
  /// file.
  uint64_t getMaxAddressOffset() const;
 
  /// Calculate the byte size of the GSYM header and tables sizes.
  ///
  /// This function will calculate the exact size in bytes of the encocded GSYM
  /// for the following items:
  /// - The GSYM header
  /// - The Address offset table
  /// - The Address info offset table
  /// - The file table
  /// - The string table
  ///
  /// This is used to help split GSYM files into segments.
  ///
  /// \returns Size in bytes the GSYM header and tables.
  uint64_t calculateHeaderAndTableSize() const;
 
  /// Copy a FunctionInfo from the \a SrcGC GSYM creator into this creator.
  ///
  /// Copy the function info and only the needed files and strings and add a
  /// converted FunctionInfo into this object. This is used to segment GSYM
  /// files into separate files while only transferring the files and strings
  /// that are needed from \a SrcGC.
  ///
  /// \param SrcGC The source gsym creator to copy from.
  /// \param FuncInfoIdx The function info index within \a SrcGC to copy.
  /// \returns The number of bytes it will take to encode the function info in
  /// this GsymCreator. This helps calculate the size of the current GSYM
  /// segment file.
  uint64_t copyFunctionInfo(const GsymCreator &SrcGC, size_t FuncInfoIdx);
 
  /// Copy a string from \a SrcGC into this object.
  ///
  /// Copy a string from \a SrcGC by string table offset into this GSYM creator.
  /// If a string has already been copied, the uniqued string table offset will
  /// be returned, otherwise the string will be copied and a unique offset will
  /// be returned.
  ///
  /// \param SrcGC The source gsym creator to copy from.
  /// \param StrOff The string table offset from \a SrcGC to copy.
  /// \returns The new string table offset of the string within this object.
  uint32_t copyString(const GsymCreator &SrcGC, uint32_t StrOff);
 
  /// Copy a file from \a SrcGC into this object.
  ///
  /// Copy a file from \a SrcGC by file index into this GSYM creator. Files
  /// consist of two string table entries, one for the directory and one for the
  /// filename, this function will copy any needed strings ensure the file is
  /// uniqued within this object. If a file already exists in this GSYM creator
  /// the uniqued index will be returned, else the stirngs will be copied and
  /// the new file index will be returned.
  ///
  /// \param SrcGC The source gsym creator to copy from.
  /// \param FileIdx The 1 based file table index within \a SrcGC to copy. A
  /// file index of zero will always return zero as the zero is a reserved file
  /// index that means no file.
  /// \returns The new file index of the file within this object.
  uint32_t copyFile(const GsymCreator &SrcGC, uint32_t FileIdx);
 
  /// Inserts a FileEntry into the file table.
  ///
  /// This is used to insert a file entry in a thread safe way into this object.
  ///
  /// \param FE A file entry object that contains valid string table offsets
  /// from this object already.
  uint32_t insertFileEntry(FileEntry FE);
 
  /// Fixup any string and file references by updating any file indexes and
  /// strings offsets in the InlineInfo parameter.
  ///
  /// When copying InlineInfo entries, we can simply make a copy of the object
  /// and then fixup the files and strings for efficiency.
  ///
  /// \param SrcGC The source gsym creator to copy from.
  /// \param II The inline info that contains file indexes and string offsets
  /// that come from \a SrcGC. The entries will be updated by coping any files
  /// and strings over into this object.
  void fixupInlineInfo(const GsymCreator &SrcGC, InlineInfo &II);
 
  /// Get the first function info address from this GSYM file.
  ///
  /// This is used to add a suffix to segmented GSYM files to indicate the first
  /// address for the first function info within the file.
  ///
  /// \returns The first function info address.
  uint64_t getFirstFunctionInfoAddress() const;
 
  /// Save this GSYM file into segments that are roughly \a SegmentSize in size.
  ///
  /// When segemented GSYM files are saved to disk, they will use \a Path as a
  /// prefix and then have the first function info address appended to the path
  /// when each segment is saved. Each segmented GSYM file has a only the
  /// strings and files that are needed to save the function infos that are in
  /// each segment. These smaller files are easy to compress and download
  /// separately and allow for efficient lookups with very large GSYM files and
  /// segmenting them allows servers to download only the segments that are
  /// needed.
  ///
  /// \param Path The path prefix to use when saving the GSYM files.
  /// \param ByteOrder The endianness to use when saving the file.
  /// \param SegmentSize The size in bytes to segment the GSYM file into.
  llvm::Error saveSegments(StringRef Path,
                           llvm::support::endianness ByteOrder,
                           uint64_t SegmentSize) const;
 
public:
  GsymCreator(bool Quiet = false);
 
  /// Save a GSYM file to a stand alone file.
  ///
  /// \param Path The file path to save the GSYM file to.
  /// \param ByteOrder The endianness to use when saving the file.
  /// \param SegmentSize The size in bytes to segment the GSYM file into. If
  ///                    this option is set this function will create N segments
  ///                    that are all around \a SegmentSize bytes in size. This
  ///                    allows a very large GSYM file to be broken up into
  ///                    shards. Each GSYM file will have its own file table,
  ///                    and string table that only have the files and strings
  ///                    needed for the shared. If this argument has no value,
  ///                    a single GSYM file that contains all function
  ///                    information will be created.
  /// \returns An error object that indicates success or failure of the save.
  llvm::Error save(StringRef Path, llvm::support::endianness ByteOrder,
                   std::optional<uint64_t> SegmentSize = std::nullopt) const;
 
  /// Encode a GSYM into the file writer stream at the current position.
  ///
  /// \param O The stream to save the binary data to
  /// \returns An error object that indicates success or failure of the save.
  llvm::Error encode(FileWriter &O) const;
 
  /// Insert a string into the GSYM string table.
  ///
  /// All strings used by GSYM files must be uniqued by adding them to this
  /// string pool and using the returned offset for any string values.
  ///
  /// \param S The string to insert into the string table.
  /// \param Copy If true, then make a backing copy of the string. If false,
  ///             the string is owned by another object that will stay around
  ///             long enough for the GsymCreator to save the GSYM file.
  /// \returns The unique 32 bit offset into the string table.
  uint32_t insertString(StringRef S, bool Copy = true);
 
  /// Insert a file into this GSYM creator.
  ///
  /// Inserts a file by adding a FileEntry into the "Files" member variable if
  /// the file has not already been added. The file path is split into
  /// directory and filename which are both added to the string table. This
  /// allows paths to be stored efficiently by reusing the directories that are
  /// common between multiple files.
  ///
  /// \param   Path The path to the file to insert.
  /// \param   Style The path style for the "Path" parameter.
  /// \returns The unique file index for the inserted file.
  uint32_t insertFile(StringRef Path,
                      sys::path::Style Style = sys::path::Style::native);
 
  /// Add a function info to this GSYM creator.
  ///
  /// All information in the FunctionInfo object must use the
  /// GsymCreator::insertString(...) function when creating string table
  /// offsets for names and other strings.
  ///
  /// \param   FI The function info object to emplace into our functions list.
  void addFunctionInfo(FunctionInfo &&FI);
 
  /// Finalize the data in the GSYM creator prior to saving the data out.
  ///
  /// Finalize must be called after all FunctionInfo objects have been added
  /// and before GsymCreator::save() is called.
  ///
  /// \param  OS Output stream to report duplicate function infos, overlapping
  ///         function infos, and function infos that were merged or removed.
  /// \returns An error object that indicates success or failure of the
  ///          finalize.
  llvm::Error finalize(llvm::raw_ostream &OS);
 
  /// Set the UUID value.
  ///
  /// \param UUIDBytes The new UUID bytes.
  void setUUID(llvm::ArrayRef<uint8_t> UUIDBytes) {
    UUID.assign(UUIDBytes.begin(), UUIDBytes.end());
  }
 
  /// Thread safe iteration over all function infos.
  ///
  /// \param  Callback A callback function that will get called with each
  ///         FunctionInfo. If the callback returns false, stop iterating.
  void forEachFunctionInfo(
      std::function<bool(FunctionInfo &)> const &Callback);
 
  /// Thread safe const iteration over all function infos.
  ///
  /// \param  Callback A callback function that will get called with each
  ///         FunctionInfo. If the callback returns false, stop iterating.
  void forEachFunctionInfo(
      std::function<bool(const FunctionInfo &)> const &Callback) const;
 
  /// Get the current number of FunctionInfo objects contained in this
  /// object.
  size_t getNumFunctionInfos() const;
 
  /// Check if an address has already been added as a function info.
  ///
  /// FunctionInfo data can come from many sources: debug info, symbol tables,
  /// exception information, and more. Symbol tables should be added after
  /// debug info and can use this function to see if a symbol's start address
  /// has already been added to the GsymReader. Calling this before adding
  /// a function info from a source other than debug info avoids clients adding
  /// many redundant FunctionInfo objects from many sources only for them to be
  /// removed during the finalize() call.
  bool hasFunctionInfoForAddress(uint64_t Addr) const;
 
  /// Set valid .text address ranges that all functions must be contained in.
  void SetValidTextRanges(AddressRanges &TextRanges) {
    ValidTextRanges = TextRanges;
  }
 
  /// Get the valid text ranges.
  const std::optional<AddressRanges> GetValidTextRanges() const {
    return ValidTextRanges;
  }
 
  /// Check if an address is a valid code address.
  ///
  /// Any functions whose addresses do not exist within these function bounds
  /// will not be converted into the final GSYM. This allows the object file
  /// to figure out the valid file address ranges of all the code sections
  /// and ensure we don't add invalid functions to the final output. Many
  /// linkers have issues when dead stripping functions from DWARF debug info
  /// where they set the DW_AT_low_pc to zero, but newer DWARF has the
  /// DW_AT_high_pc as an offset from the DW_AT_low_pc and these size
  /// attributes have no relocations that can be applied. This results in DWARF
  /// where many functions have an DW_AT_low_pc of zero and a valid offset size
  /// for DW_AT_high_pc. If we extract all valid ranges from an object file
  /// that are marked with executable permissions, we can properly ensure that
  /// these functions are removed.
  ///
  /// \param Addr An address to check.
  ///
  /// \returns True if the address is in the valid text ranges or if no valid
  ///          text ranges have been set, false otherwise.
  bool IsValidTextAddress(uint64_t Addr) const;
 
  /// Set the base address to use for the GSYM file.
  ///
  /// Setting the base address to use for the GSYM file. Object files typically
  /// get loaded from a base address when the OS loads them into memory. Using
  /// GSYM files for symbolication becomes easier if the base address in the
  /// GSYM header is the same address as it allows addresses to be easily slid
  /// and allows symbolication without needing to find the original base
  /// address in the original object file.
  ///
  /// \param  Addr The address to use as the base address of the GSYM file
  ///              when it is saved to disk.
  void setBaseAddress(uint64_t Addr) {
    BaseAddress = Addr;
  }
 
  /// Whether the transformation should be quiet, i.e. not output warnings.
  bool isQuiet() const { return Quiet; }
 
 
  /// Create a segmented GSYM creator starting with function info index
  /// \a FuncIdx.
  ///
  /// This function will create a GsymCreator object that will encode into
  /// roughly \a SegmentSize bytes and return it. It is used by the private
  /// saveSegments(...) function and also is used by the GSYM unit tests to test
  /// segmenting of GSYM files. The returned GsymCreator can be finalized and
  /// encoded.
  ///
  /// \param [in] SegmentSize The size in bytes to roughly segment the GSYM file
  /// into.
  /// \param [in,out] FuncIdx The index of the first function info to encode
  /// into the returned GsymCreator. This index will be updated so it can be
  /// used in subsequent calls to this function to allow more segments to be
  /// created.
  /// \returns An expected unique pointer to a GsymCreator or an error. The
  /// returned unique pointer can be NULL if there are no more functions to
  /// encode.
  llvm::Expected<std::unique_ptr<GsymCreator>>
  createSegment(uint64_t SegmentSize, size_t &FuncIdx) const;
};
 
} // namespace gsym
} // namespace llvm
 
#endif // LLVM_DEBUGINFO_GSYM_GSYMCREATOR_H