Re: [patch gas]: Add pseudos for generation of runtime function entries by gas

[Kai Tietz <ktietz70 at googlemail dot com>]

2009/8/31 H.J. Lu <hjl.tools@gmail.com>:
> On Tue, Aug 11, 2009 at 3:28 AM, Kai Tietz<ktietz70@googlemail.com> wrote:
>> Hello,
>>
>> I would like to show the patch for .pdata and .xdata generation of
>> pe-coff targets via gas, and to get some feed-back.
>> This patch includes support for arm, ppc, arm, sh (3&4), mips, and
>> x64. As for x86 there is no OS support for runtime function
>> information, I spared this part. It would just increase executable
>> size for x86 PE and there is no real gain for this target.
>>
>> Short overview:
>> ?There are at the moment three different function entry formats preset.
>> ?The first is the MIPS one (could be also used here for x86). The
>> second version is for ARM, PPC, SH3, and SH4 mainly for Windows CE.
>> The third is the IA64 and x64 version. Note, the IA64 isn't
>> implemented yet, but to find information about it, please see
>> specification about IA64 on
>> http://download.intel.com/design/Itanium/Downloads/245358.pdf file.
>>
>> ?The first version has just entries in the pdata section:
>> BeginAddress, EndAddress, ExceptionHandler, HandlerData, and
>> PrologueEndAddress. Each value is a pointer to the corresponding data
>> and has size of 4 bytes.
>>
>> ?The second variant has the following entries in the pdata section.
>> BeginAddress, PrologueLength (8 bits), EndAddress (22 bits),
>> Use-32-bit-instruction (1 bit), and Exception-Handler-Exists (1 bit).
>> If the FunctionLength is zero, or the Exception-Handler-Exists bit is
>> true, a PDATA_EH block is placed directly before function entry
>> (expressed by .seh_eh pseudo).
>>
>> ?The third version has a function entry block of BeginAddress (RVA),
>> EndAddress (RVA), and UnwindData (RVA). The description of the
>> prologue, excepetion-handler, and additional SEH data is stored within
>> the UNWIND_DATA field in the xdata section.
>>
>> ?The pseudos:
>> ?.seh_proc <fct_name>
>> ? ? This specifies, that a SEH block begins for the function
>> <fct_name>. This is valid for all targets.
>> ?.seh_endprologue
>> ? ? By this pseudo the location of the prologue end-address (taken by
>> the current code address of the appearance of this pseudo). Valid for
>> all targets.
>> ?.seh_handler <handler>[,<handler-data>]
>> ? ?This pseudo specifies the handler function to be used. For version
>> 2 the handler-data field specifies the user optional data block. For
>> version 3 the handler-data field can be a rva to user-data (for
>> FHANDLER), if the name is @unwind the UHANDLER unwind block is
>> generated, and if it is @except (or not specified at all) EHANDLER
>> exception block is generated.
>> ?.seh_eh
>> ? ?This pseudo is used for version 2 to indicate the location of the
>> function begin in assembly. Here the PDATA_EH data is may stored to.
>> ?.seh_32/.seh_no32
>> ? This pseudos are just used for version 2 (see above for
>> description). At the moment it defaults to no32, if not specified.
>> ?.seh_endproc
>> ? By this pseudo the end of the SEH block is specified.
>> ?.seh_setframe <reg>,<offset>
>> ? ?By this pseudo the frame-register and the offset (value between
>> 0-240 with 16-byte alignment) can be specified. This is just used by
>> version 3.
>> ?.seh_stackalloc <size>
>> ? ?By this stack allocation in code is described for version 3.
>> ?.seh_pushreg <reg>
>> ? ?By this a general register push in code is described for version 3.
>> ?.seh_savereg <reg>
>> ? ?By this a general register save to memory in code is described for
>> version 3.
>> ?.seh_savemm <mm>
>> ? ?By this a mm register save to memory in code is described for version 3.
>> ?.seh_savexmm
>> ? ?By this a xmm register save to memory in code is described for version 3.
>> ?.seh_pushframe
>> ? ?By this information about entry kind can be described for version 3.
>> ?.seh_scope <begin>,<end>,<handler>,<jump>
>> ? ?By this SCOPED entries for unwind or exceptions can be specified
>> for version 3. This is just valid for UHANDLE and EHANDLER xdata
>> descriptor and a global handler has to be specified. For handler and
>> jump arguments, names of @1,@0, and @null can be used and they are
>> specifying that a constant instead of a rva has to be used.
>>
>> 2009-08-11 ?Kai Tietz ?<kai.tietz@onevision.com>
>>
>> ? ? ? ?* config/obj-coff-seh.c: New file.
>> ? ? ? ?* config/obj-coff-seh.h: Likewise.
>> ? ? ? ?* config/obj-coff.c (obj-coff-seh.c): Add include.
>> ? ? ? ?(coff_pseudo_table): Add new .seh... commands.
>> ? ? ? ?* config/obj-coff.h (obj_coff_seh_do_final): Add new
>> ? ? ? ?function prototype.
>> ? ? ? ?(obj_coff_generate_pdata): New obj-coff hook.
>> ? ? ? ?* gas/write.c (size_seg): Avoid sizing of already sized
>> ? ? ? ?sections.
>> ? ? ? ?(write_object_file): Call conditional hook
>> ? ? ? ?objc_coff_generate_pdata.
>> ? ? ? ?* Makefile.in: Add dependencies for new files.
>> ? ? ? ?* Makefile.am: Regenerated.
>>
>> Tested for x86_64-pc-mingw32, i686-pc-linux, x86_64-pc-linux,
>> i686-pc-mingw32, and for cygwin. Base test I did for mips and arm.
>> This patch needs additional documentation in gas, and a lot of tests,
>> but first I would like to get response about it.
>>
>
> This patch has an accidental change in write.c:
>
> -#ifdef tc_frob_file_after_relocs
> +#ifdef tc_frob_file_after_reloc
> ? tc_frob_file_after_relocs ();
> ?#endif
> ?#ifdef obj_frob_file_after_relocs
> ? obj_frob_file_after_relocs ();
> ?#endif
>
> It caused:
>
> http://sourceware.org/bugzilla/show_bug.cgi?id=10570
>
> I checked in the enclosed patch to fix it.
>
> --
> H.J.
> ---
> Index: ChangeLog
> ===================================================================
> --- ChangeLog ? (revision 6668)
> +++ ChangeLog ? (working copy)
> @@ -1,3 +1,9 @@
> +2009-08-31 ?H.J. Lu ?<hongjiu.lu@intel.com>
> +
> + ? ? ? PR gas/10570
> + ? ? ? * write.c (write_object_file): Revert the accidental change
> + ? ? ? made in revision 1.124 on 2009-08-17.
> +
> ?2009-08-31 ?Jan Beulich ?<jbeulich@novell.com>
>
> ? ? ? ?* config/obj-elf.c (obj_elf_change_section): Set default type
> Index: write.c
> ===================================================================
> --- write.c ? ? (revision 6668)
> +++ write.c ? ? (working copy)
> @@ -1894,12 +1894,13 @@ write_object_file (void)
> ?#endif
> ? bfd_map_over_sections (stdoutput, write_relocs, (char *) 0);
>
> -#ifdef tc_frob_file_after_reloc
> +#ifdef tc_frob_file_after_relocs
> ? tc_frob_file_after_relocs ();
> ?#endif
> ?#ifdef obj_frob_file_after_relocs
> ? obj_frob_file_after_relocs ();
> ?#endif
> +
> ? bfd_map_over_sections (stdoutput, write_contents, (char *) 0);
> ?}
>

Sorry,
Kai

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