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Re: RELASZ is set to 0 on x86_64 when developing EFI applications with gnu-efi
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: éæ <yanmiaobest at gmail dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Mon, 9 Jun 2014 08:32:11 -0700
- Subject: Re: RELASZ is set to 0 on x86_64 when developing EFI applications with gnu-efi
- Authentication-results: sourceware.org; auth=none
- References: <CAPc5xaNRCsvytiQKi52Kkimk_Qs5cFRycCy3y0hTUBNYZOb-RQ at mail dot gmail dot com> <CAMe9rOox_pqo+M6Y3NPP7fjVP5pF8woO_rA9O265gAGasxyLVg at mail dot gmail dot com> <CAPc5xaMAvYt5TKWJufvhEhUK031roZMU4=zHdLnk=MDeuoJ8Sw at mail dot gmail dot com>
On Sun, Jun 8, 2014 at 7:07 PM, éæ <yanmiaobest@gmail.com> wrote:
> Forgot to cc the list.
>
> 2014-06-06 23:08 GMT+08:00 H.J. Lu <hjl.tools@gmail.com>:
>> On Fri, Jun 6, 2014 at 12:21 AM, éæ <yanmiaobest@gmail.com> wrote:
>>> Hi Experts,
>>>
>>> I am developing EFI applications using gnu-efi library and I
>>> need to use some of the existing code base which groups initialization
>>> functions together in a special section.
>>>
>>> The gnu-efi library uses the symbol _DYNAMIC to locate the
>>> relocation section and does fixups before calling main. Without the
>>> special section for init functions, there is only a '.rela' section
>>> pointed by _DYMAMIC and everything works fine. But after I modified
>>> the default linker script, the produced ELF image contains 2
>>> relocation sections:
>>> --------------------------------------------------------------------------------------------------------------
>>> Relocation section '.rela.dyn' at offset 0x23850 contains 1 entries:
>>> Offset Info Type Sym. Value Sym. Name + Addend
>>> 000000027de0 000000000008 R_X86_64_RELATIVE 000000000000b7d0
>>>
>>
>> What change you made causes rela.dyn section?
>
>
> In one of the source file, I have:
>
> void xxxInit(void)
> {
> ....
> }
> static void * __func_xxxInit
> __attribute__((section(".init.
> before.shell"))) = (void *)xxxInit;
You put a function pointer, which is in data section, in
".init.before.shell" section, which you put in text
section in linker script:
.text :
{
*(.text)
/* XXX: added for constructors */
init_start = .;
KEEP(*(.init.before.memory))
einit_before_memory = .;
KEEP(*(.init.before.fs))
einit_before_fs = .;
KEEP(*(.init.before.shell))
einit_before_shell = .;
/* XXX: added for constructors */
}
Did you want to put the function xxxInit in .init.before.shell?
> And in linker script I added this:
>
> KEEP(*(.init.before.shell))
> einit_before_shell = .;
>
> The relocation entry is for the function pointer. If I remove the
> "__attribute__((section(...)))" part, then
> the problem disappears.
>
> Thanks,
> Miao
--
H.J.