LLVM  12.0.0git
llvm::gsym::GsymCreator Class Reference

GsymCreator is used to emit GSYM data to a stand alone file or section within a file. More...

#include "llvm/DebugInfo/GSYM/GsymCreator.h"

## Public Member Functions

GsymCreator ()

llvm::Error save (StringRef Path, llvm::support::endianness ByteOrder) const
Save a GSYM file to a stand alone file. More...

llvm::Error encode (FileWriter &O) const
Encode a GSYM into the file writer stream at the current position. More...

uint32_t insertString (StringRef S, bool Copy=true)
Insert a string into the GSYM string table. More...

uint32_t insertFile (StringRef Path, sys::path::Style Style=sys::path::Style::native)
Insert a file into this GSYM creator. More...

Add a function info to this GSYM creator. More...

llvm::Error finalize (llvm::raw_ostream &OS)
Finalize the data in the GSYM creator prior to saving the data out. More...

void setUUID (llvm::ArrayRef< uint8_t > UUIDBytes)
Set the UUID value. More...

void forEachFunctionInfo (std::function< bool(FunctionInfo &)> const &Callback)
Thread safe iteration over all function infos. More...

void forEachFunctionInfo (std::function< bool(const FunctionInfo &)> const &Callback) const
Thread safe const iteration over all function infos. More...

size_t getNumFunctionInfos () const
Get the current number of FunctionInfo objects contained in this object. More...

Set valid .text address ranges that all functions must be contained in. More...

Get the valid text ranges. More...

Set the base address to use for the GSYM file. More...

## Detailed Description

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:

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:

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".

Definition at line 134 of file GsymCreator.h.

## ◆ GsymCreator()

 GsymCreator::GsymCreator ( )

Definition at line 24 of file GsymCreator.cpp.

References insertFile().

## Member Function Documentation

 void GsymCreator::addFunctionInfo ( FunctionInfo && FI )

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.

Parameters
 FI The function info object to emplace into our functions list.

Definition at line 282 of file GsymCreator.cpp.

Referenced by llvm::gsym::ObjectFileTransformer::convert().

## ◆ encode()

 llvm::Error GsymCreator::encode ( FileWriter & O ) const

Encode a GSYM into the file writer stream at the current position.

Parameters
 O The stream to save the binary data to
Returns
An error object that indicates success or failure of the save.

Definition at line 59 of file GsymCreator.cpp.

Referenced by save().

## ◆ finalize()

 llvm::Error GsymCreator::finalize ( llvm::raw_ostream & OS )

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.

Parameters
 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.

Definition at line 164 of file GsymCreator.cpp.

## ◆ forEachFunctionInfo() [1/2]

 void GsymCreator::forEachFunctionInfo ( std::function< bool(FunctionInfo &)> const & Callback )

Thread safe iteration over all function infos.

Parameters
 Callback A callback function that will get called with each FunctionInfo. If the callback returns false, stop iterating.

Definition at line 288 of file GsymCreator.cpp.

Referenced by setUUID().

## ◆ forEachFunctionInfo() [2/2]

 void GsymCreator::forEachFunctionInfo ( std::function< bool(const FunctionInfo &)> const & Callback ) const

Thread safe const iteration over all function infos.

Parameters
 Callback A callback function that will get called with each FunctionInfo. If the callback returns false, stop iterating.

Definition at line 297 of file GsymCreator.cpp.

## ◆ getNumFunctionInfos()

 size_t GsymCreator::getNumFunctionInfos ( ) const

Get the current number of FunctionInfo objects contained in this object.

Definition at line 306 of file GsymCreator.cpp.

Referenced by llvm::gsym::ObjectFileTransformer::convert(), and setUUID().

## ◆ GetValidTextRanges()

 const Optional llvm::gsym::GsymCreator::GetValidTextRanges ( ) const
inline

Get the valid text ranges.

Definition at line 253 of file GsymCreator.h.

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.

Definition at line 317 of file GsymCreator.cpp.

Referenced by llvm::gsym::ObjectFileTransformer::convert(), and setUUID().

## ◆ insertFile()

 uint32_t GsymCreator::insertFile ( StringRef Path, sys::path::Style Style = sys::path::Style::native )

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.

Parameters
 Path The path to the file to insert. Style The path style for the "Path" parameter.
Returns
The unique file index for the inserted file.

Definition at line 28 of file GsymCreator.cpp.

Referenced by llvm::gsym::CUInfo::DWARFToGSYMFileIndex(), and GsymCreator().

## ◆ insertString()

 uint32_t GsymCreator::insertString ( StringRef S, bool Copy = true )

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.

Parameters
 S The string to insert into the string table. 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.

Definition at line 264 of file GsymCreator.cpp.

Referenced by llvm::gsym::ObjectFileTransformer::convert(), getQualifiedNameIndex(), and insertFile().

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.

Parameters
Returns
True if the address is in the valid text ranges or if no valid text ranges have been set, false otherwise.

Definition at line 311 of file GsymCreator.cpp.

Referenced by llvm::gsym::ObjectFileTransformer::convert(), and GetValidTextRanges().

## ◆ save()

 llvm::Error GsymCreator::save ( StringRef Path, llvm::support::endianness ByteOrder ) const

Save a GSYM file to a stand alone file.

Parameters
 Path The file path to save the GSYM file to. ByteOrder The endianness to use when saving the file.
Returns
An error object that indicates success or failure of the save.

Definition at line 49 of file GsymCreator.cpp.

References encode(), llvm::errorCodeToError(), and llvm::RISCVFenceField::O.

inline

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.

Parameters
 Addr The address to use as the base address of the GSYM file when it is saved to disk.

Definition at line 289 of file GsymCreator.h.

## ◆ setUUID()

 void llvm::gsym::GsymCreator::setUUID ( llvm::ArrayRef< uint8_t > UUIDBytes )
inline

Set the UUID value.

Parameters
 UUIDBytes The new UUID bytes.

Definition at line 214 of file GsymCreator.h.

Referenced by llvm::gsym::ObjectFileTransformer::convert().

## ◆ SetValidTextRanges()

 void llvm::gsym::GsymCreator::SetValidTextRanges ( AddressRanges & TextRanges )
inline

Set valid .text address ranges that all functions must be contained in.

Definition at line 248 of file GsymCreator.h.

The documentation for this class was generated from the following files: