Re: [PATCH v2] Fix WOW64 process system DLL paths

[Jon Turney <jon.turney@dronecode.org.uk>]

On 24/03/2020 19:23, Hannes Domani via Gdb-patches wrote:
> GetModuleFileNameEx returns for some DLLs of WOW64 processes
> the path inside the 64bit system directory instead of the 32bit
> syswow64 directory.
> 
> Problem happens e.g. with dbghelp.dll:
> 
> (gdb) start
> Temporary breakpoint 1 at 0x415a00: file fiber.cpp, line 430.
> Starting program: C:\src\tests\fiber.exe
> warning: `C:\Windows\system32\dbghelp.dll': Shared library architecture i386:x86-64 is not compatible with target architecture i386.
> 
> Temporary breakpoint 1, main () at fiber.cpp:430
> 430     {
> (gdb) info sharedlibrary
>  From        To          Syms Read   Shared Object Library
> 0x77070000  0x771d4d20  Yes (*)     C:\Windows\SysWOW64\ntdll.dll
> 0x74dc0000  0x74ebad9c  Yes (*)     C:\Windows\syswow64\kernel32.dll
> 0x75341000  0x75386a18  Yes (*)     C:\Windows\syswow64\KernelBase.dll
> 0x6f6a1000  0x6f7c48fc  Yes (*)     C:\Windows\system32\dbghelp.dll
> 0x74d01000  0x74dab2c4  Yes (*)     C:\Windows\syswow64\msvcrt.dll
> (*): Shared library is missing debugging information.
> 
> This detects this situation and converts the DLL path to the
> syswow64 equivalent.
> 
[...]
>   #else
>         name = dll_name;
>   #endif
> +#ifdef __x86_64__
> +      /* Convert the DLL path of WOW64 processes returned by
> +	 GetModuleFileNameEx from the 64bit system directory to the
> +	 32bit syswow64 directory if necessary.  */
> +      std::string syswow_dll_path;
> +      if (wow64_process
> +	  && strncasecmp (name, system_dir, system_dir_len) == 0
> +	  && strchr (name + system_dir_len, '\\') == nullptr)
> +	{
> +	  syswow_dll_path = syswow_dir;
> +	  syswow_dll_path += name + system_dir_len;
> +	  name = syswow_dll_path.c_str();
> +	}
> +#endif
>   

DLLs we become aware of via handle_load_dll() don't get this treatment.

Can you share your reasoning about that?