[PATCH v4] covoar: Handle periods in symbols from objdump

[Alex White]

ping

> -----Original Message-----
> From: Alex White <alex.white at oarcorp.com>
> Sent: Friday, March 19, 2021 2:10 PM
> To: devel at rtems.org
> Cc: Alex White <alex.white at oarcorp.com>
> Subject: [PATCH v4] covoar: Handle periods in symbols from objdump
> 
> Occasionally the compiler will generate symbols that look similar to symbols
> defined in RTEMS code except that they contain some suffix.
> These symbol suffixes are only found in the ELF symbol table; the symbols
> appear to be normal in the DWARF info. This appears to be happening on all
> architectures.
> 
> For example, the function _Message_queue_Create from rtems appears as
> "_Message_queue_Create.part.0". Other suffixes include ".isra.0",
> ".constprop.0", and ".0".
> 
> This looks to be related to compiler optimizations. Symbols with suffixes
> were being treated as unique. For our purposes, they should be mapped to
> the equivalent symbols in the DWARF info. This has been fixed.
> ---
>  tester/covoar/ExecutableInfo.cc   |  3 +--
>  tester/covoar/ObjdumpProcessor.cc | 15 +++++++++++++++
>  tester/covoar/SymbolTable.cc      | 12 +++++++++---
>  3 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/tester/covoar/ExecutableInfo.cc
> b/tester/covoar/ExecutableInfo.cc index c996d75..1e14721 100644
> --- a/tester/covoar/ExecutableInfo.cc
> +++ b/tester/covoar/ExecutableInfo.cc
> @@ -118,8 +118,7 @@ namespace Coverage {
>      // Obtain the coverage map containing the specified address.
>      itsSymbol = theSymbolTable.getSymbol( address );
>      if (itsSymbol != "") {
> -      it = coverageMaps.find( itsSymbol );
> -      aCoverageMap = (*it).second;
> +      aCoverageMap = &findCoverageMap(itsSymbol);
>      }
> 
>      return aCoverageMap;
> diff --git a/tester/covoar/ObjdumpProcessor.cc
> b/tester/covoar/ObjdumpProcessor.cc
> index 0647ff9..e19fa92 100644
> --- a/tester/covoar/ObjdumpProcessor.cc
> +++ b/tester/covoar/ObjdumpProcessor.cc
> @@ -417,6 +417,21 @@ namespace Coverage {
>          processSymbol = false;
>          theInstructions.clear();
> 
> +        // Look for a '.' character and strip everything after it.
> +        // There is a chance that the compiler splits function bodies to improve
> +        // inlining. If there exists some inlinable function that contains a
> +        // branch where one path is more expensive and less likely to be taken
> +        // than the other, inlining only the branch instruction and the less
> +        // expensive path results in smaller code size while preserving most of
> +        // the performance improvement.
> +        // When this happens, the compiler will generate a function with a
> +        // ".part.n" suffix. For our purposes, this generated function part is
> +        // equivalent to the original function and should be treated as such.
> +        char *periodIndex = strstr(symbol, ".");
> +        if (periodIndex != NULL) {
> +          *periodIndex = 0;
> +        }
> +
>          // See if the new symbol is one that we care about.
>          if (SymbolsToAnalyze->isDesired( symbol )) {
>            currentSymbol = symbol;
> diff --git a/tester/covoar/SymbolTable.cc b/tester/covoar/SymbolTable.cc
> index 53bc8af..00062cc 100644
> --- a/tester/covoar/SymbolTable.cc
> +++ b/tester/covoar/SymbolTable.cc
> @@ -46,12 +46,18 @@ namespace Coverage {
>      symbolData.startingAddress = start;
>      symbolData.length = length;
> 
> -    if ( info[ symbol ].empty() == false ) {
> -      if ( info[ symbol ].front().length != length ) {
> +    for (auto& symData : info[ symbol ]) {
> +      // The starting address could differ since we strip any suffixes beginning
> +      // with a '.'
> +      if (symData.startingAddress != start) {
> +        continue;
> +      }
> +
> +      if (symData.length != length) {
>          std::ostringstream what;
>          what << "Different lengths for the symbol "
>               << symbol
> -             << " (" << info[ symbol ].front().length
> +             << " (" << symData.length
>               << " and " << length
>               << ")";
>          throw rld::error( what, "SymbolTable::addSymbol" );
> --
> 2.27.0