This is the mail archive of the mailing list for the binutils project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: MIPS stubs in Gold

Hi gain,
After some time I have to bother you again. I need some additional
details about ARM implementation of stubs and few tips how to implement
them for MIPS.

Situation is as follows:
Some function calls need special handling depend on flags and relocation
type. In that case, some additional stub code is needed. There are two
types of stubs. One that goes immediately before function and it only
contains loading of function address in some register and second that
goes on arbitrary place in .text section (usually at the end) and
contains loading of function address in some register and jump to that
function. Also, relocations that are related to that function call has
to be changed in a way to point to that new code. New relocation has to
be added to the stub code to fix function address in it. Additional
problem for the first type of stub is that is has to be just before
function in .text section (it is only used if function is at the
beginning of the .text section).

I looked at ARM code, also I looked at implementation of plt, but I
didn't manage to find what I needed.

Can someone give me some hints or ideas what to do and how to proceed
with this? Also, which details can help and which can't (there are quite
some code in ARM implementation of Gold :-)).

Thank you in advance for your help,

On 01/06/2011 20:21, Doug Kwan (éæå) wrote:
> The ARM stubs do a number of things
> -extending branch range
> -handling transistion between ARM and THUMB with BX and BLX
> instructions cannot be used.
> -avoid a hardware erratum in involving page straddling long branches
> in THUMB2 mode.
> The base class is Stub, from which other stub kinds are derived.  Stub
> generation in ARM is a relaxation.  I need to iterate a number of time
> because addresses are changed by the inserted stubs.  I hope that this
> is not the case in MIPS.  There are hooks for doing relaxation.  Look
> for do_relax() in the ARM backend.
> -Doug
> On Wed, Jun 1, 2011 at 8:43 AM, Ian Lance Taylor <> wrote:
>> Aleksandar Simeonov <> writes:
>>> Again I have problem that occupy me for some time and for what I can't
>>> find solution. Situation is as follows (next text is taken from
>>> elfxx-mips.c from ld):
>>> "Information about a non-PIC interface to a PIC function.  There are
>>>    two ways of creating these interfaces.  The first is to add:
>>>       lui     $25,%hi(func)
>>>       addiu   $25,$25,%lo(func)
>>>    immediately before a PIC function "func".  The second is to add:
>>>       lui     $25,%hi(func)
>>>       j       func
>>>       addiu   $25,$25,%lo(func)
>>>    to a separate trampoline section.
>>>    Stubs of the first kind go in a new section immediately before the
>>>    target function.  Stubs of the second kind go in a single section
>>>    pointed to by the hash table's "strampoline" field."
>>> I tried to find something similar in Gold for other architectures, but
>>> without success. Can you give me some suggestions where to look and what
>>> to do to implement this.
>> The ARM backend implements stubs, e.g., for calls between ARM and Thumb
>> code.  Search for "stub" and "Stub".  You probably don't have to do
>> anything as complex for the MIPS backend.  At least, I hope not.
>> Ian

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]