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Altera_Forum
Honored Contributor I
751 Views

FLTK demo apps on uClinux-MMU

Hello! 

 

First I'd like to thank all the people on this board. I got lots of useful information from reading your postings. Now it's time for my first write activity. 

 

My problem here is the following: 

 

I'm using the MMU distribution of nios2-linux and like to build fltk applications.  

 

As Kazuyasu's mentioned in his post 

 

linux with mmu on neek, page 2 

 

I get the same segfaults, so there is a problem with the libraries. 

 

Has anybody found out the problem with linking libnano-X statically? And is there another possible solution than building the libnano-X dynamically? 

 

Thanks, 

steron
0 Kudos
6 Replies
Altera_Forum
Honored Contributor I
51 Views

Hi, 

 

 

--- Quote Start ---  

 

And is there another possible solution than building the libnano-X dynamically? 

 

--- Quote End ---  

 

 

This problem is caused by the incomplete implementation of 'tool chains' and there is no way of work-around except to implement those correctly. 

And moreover, there is a problem that the size of GOT(Global Offset Table) is limited within 32Kbytes. This fact is not documented at all, but last week I had finally trodden on the tiger's tail. 

nios2-wrs-linux-gnu-gcc -I/mnt/usr/include -Wl,-rpath /mnt/usr/lib -g -shared .libs/gtkquery.o .libs/gtksearchengine.o .libs/gtksearchenginesimple.o .libs/fnmatch.o .libs/gtkaboutdialog.o .libs/gtkaccelgroup.o .libs/gtkaccellabel.o .libs/gtkaccelmap.o .libs/gtkaccessible.o .libs/gtkaction.o .libs/gtkactiongroup.o .libs/gtkadjustment.o .libs/gtkalignment.o .libs/gtkarrow.o .libs/gtkaspectframe.o ............... .-Wl,--whole-archive xdgmime/.libs/libxdgmime.a -Wl,--no-whole-archive -Wl,--rpath -Wl,/home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gdk-pixbuf/.libs -Wl,--rpath -Wl,/home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gdk/.libs -Wl,--rpath -Wl,/mnt/usr//lib -Wl,--rpath -Wl,/home/hamada/nios2-linux/uClinux-dist/staging/usr/lib -Wl,--rpath -Wl,/mnt/usr/lib -Wl,--rpath -Wl,/mnt/usr/lib -Wl,--rpath -Wl,/mnt/usr//lib -Wl,--rpath -Wl,/home/hamada/nios2-linux/uClinux-dist/staging/usr/lib -L/home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gdk-pixbuf/.libs -L/mnt/usr/lib/ ../gdk-pixbuf/.libs/libgdk_pixbuf-2.0.so -L/mnt/usr/lib ../gdk/.libs/libgdk-x11-2.0.so -L/mnt/usr//lib -L/home/hamada/nios2-linux/uClinux-dist/staging/usr/lib/ -L/home/hamada/nios2-linux/uClinux-dist/staging/usr/lib /mnt/usr//lib/libpangocairo-1.0.so /mnt/usr//lib/libpango-1.0.so /home/hamada/nios2-linux/uClinux-dist/staging/usr/lib/libX11.so /mnt/usr//lib/libXcomposite.so /mnt/usr//lib/libXdamage.so /mnt/usr//lib/libXfixes.so /mnt/usr//lib/libatk-1.0.so /mnt/usr/lib/libgobject-2.0.so /mnt/usr/lib/libgmodule-2.0.so /mnt/usr/lib/libglib-2.0.so /mnt/usr//lib/libcairo.so -lm -Wl,-rpath -Wl,-soname -Wl,-version-script -Wl,.libs/libgtk-x11-2.0.ver -o .libs/libgtk-x11-2.0.so.0.1200.12 /home/hamada/nios2-linux/toolchain-mmu/x86-linux2/bin/../lib/gcc/nios2-wrs-linux-gnu/4.1.2/crtbeginS.o: In function `__do_global_dtors_aux': crtstuff.c:(.text+0x2c): relocation truncated to fit: R_NIOS2_GOT16 against `__cxa_finalize@@GLIBC_2.10' crtstuff.c:(.text+0x34): relocation truncated to fit: R_NIOS2_GOT16 against `__dso_handle' crtstuff.c:(.text+0x3c): relocation truncated to fit: R_NIOS2_CALL16 against `__cxa_finalize@@GLIBC_2.10' /home/hamada/nios2-linux/toolchain-mmu/x86-linux2/bin/../lib/gcc/nios2-wrs-linux-gnu/4.1.2/crtbeginS.o: In function `frame_dummy': crtstuff.c:(.text+0xdc): relocation truncated to fit: R_NIOS2_GOT16 against `_Jv_RegisterClasses' /home/hamada/nios2-linux/toolchain-mmu/x86-linux2/bin/../lib/gcc/nios2-wrs-linux-gnu/4.1.2/crtendS.o: In function `__do_global_ctors_aux': crtstuff.c:(.text+0x18): relocation truncated to fit: R_NIOS2_GOT16 against `__CTOR_END__' /home/hamada/nios2-linux/toolchain-mmu/x86-linux2/bin/../lib/gcc/nios2-wrs-linux-gnu/4.1.2/crtendS.o:(.init+0x0): relocation truncated to fit: R_NIOS2_CALL16 against `__do_global_ctors_aux' .libs/gtkquery.o: In function `finalize': /home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gtk/gtkquery.c:44: relocation truncated to fit: R_NIOS2_CALL16 against `g_free' .libs/gtkquery.o: In function `_gtk_query_init': /home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gtk/gtkquery.c:63: relocation truncated to fit: R_NIOS2_CALL16 against `_gtk_query_get_type' .libs/gtkquery.o: In function `_gtk_query_new': /home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gtk/gtkquery.c:69: relocation truncated to fit: R_NIOS2_CALL16 against `_gtk_query_get_type' .libs/gtkquery.o: In function `_gtk_query_set_text': /home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gtk/gtkquery.c:83: relocation truncated to fit: R_NIOS2_CALL16 against `g_free' .libs/gtkquery.o: In function `_gtk_query_set_location': /home/hamada/nios2-linux/uClinux-dist/lib/gtk+-2.12.12/gtk/gtkquery.c:97: additional relocation overflows omitted from the output collect2: ld returned 1 exit status Of course, All sources are compiled with '-fPIC', but nios2's compiler generates the code for dynamic linking like 

g_free (query->priv->text); 1ac: e0bffe17 ldw r2,-8(fp) 1b0: 10800317 ldw r2,12(r2) 1b4: 11000017 ldw r4,0(r2) 1b8: b0800017 ldw r2,0(r22) 1bc: 103ee83a callr r2 and the relocation information is like 

 

00000198 0000181a R_NIOS2_PCREL_LO 00000000 _GLOBAL_OFFSET_TABLE_ + 4 000001b8 00001f17 R_NIOS2_CALL16 00000000 g_free + 0 000001c0 00000916 R_NIOS2_GOT16 00000000 _gtk_query_parent_clas + 0

 

So we can't have a GTO which size is more than 32Kbyte and this is caused by the incomplete compiler implementations for code generations. 

 

---nios2.md--- ;; FIXME:these uses look unnecessary. (define_insn "pic_load_addr" UNSPEC_PIC_SYM)) (use (match_dup 1))] "flag_pic" "ldw\\t%0, %%got(%2)(%1)") (define_insn "pic_load_call_addr" UNSPEC_PIC_CALL_SYM)) (use (match_dup 1))] "flag_pic" "ldw\\t%0, %%call(%2)(%1)") ;; TLS support But who will repair those? 

 

Kazu
Altera_Forum
Honored Contributor I
51 Views

Some time ago already... 

thanks for your reply, Kazu. 

 

Anyway, I decided to build the library as an shared object.
Altera_Forum
Honored Contributor I
51 Views

Thank you for the precise analysis! 

 

Some additional comments: 

 

1) http://www.altera.com/literature/hb/nios2/n2cpu_nii5v1.pdf 7-12 documents the 64KB GOT limit: 

Because the GOT-relative and TP-relative relocations are 16-bit relocations, no single  

object file can require more than 64 KB of GOT and no dynamic object using local  

dynamic or local executable thread-local storage (TLS) can have more than 64 KB of  

TLS data. New relocations might be added to support this in the future. 

 

It may be time to think about the mentioned future support for larger GOT via -fPIC. 

 

2) To date this limitation seems to mainly affect C++ programs. C++ apparently likes to generate lots of global symbols. This URL documents a C++ library with 200,000 global symbols: http://gcc.gnu.org/wiki/visibility. Clearly that would swamp a 64KB GOT table, at least when naively used. (-fsection-anchors sounds like an attempt to be smarter about such things, but is apparently not supported on Nios2, at least as yet.) 

 

3) I have one report of -Os (or -O2) resolving a similar issue. This is a workaround rather than a fix, but might be useful all the same.
Altera_Forum
Honored Contributor I
51 Views

Hi, 

 

 

--- Quote Start ---  

 

1) http://www.altera.com/literature/hb/nios2/n2cpu_nii5v1.pdf 7-12 documents the 64KB GOT limit: 

Because the GOT-relative and TP-relative relocations are 16-bit relocations, no single  

object file can require more than 64 KB of GOT and no dynamic object using local  

dynamic or local executable thread-local storage (TLS) can have more than 64 KB of  

TLS data. New relocations might be added to support this in the future. 

 

It may be time to think about the mentioned future support for larger GOT via -fPIC. 

 

--- Quote End ---  

 

 

I don't know the recent situation, but I've posted an implimentation 

 

http://www.alteraforum.com/forum/showthread.php?t=26331 

 

, though it is not so complete. And I experienced the problem when my program grew beyond 32KB GOT boundary, not 64KB. 

 

Kazu
Altera_Forum
Honored Contributor I
51 Views

 

--- Quote Start ---  

Hi, 

 

I don't know the recent situation, but I've posted an implementation 

 

http://www.alteraforum.com/forum/showthread.php?t=26331 

 

--- Quote End ---  

 

 

That's a slick-looking patch! I've forwarded it to Walter Goosens (nios2-dev) who has encountered a similar problem. (For the moment he seems to be able to get around it by using -Os.) I'd like to see it (or something similar) upstreamed to the mainline gcc codebase... 

 

 

--- Quote Start ---  

And I experienced the problem when my program grew beyond 32KB GOT boundary, not 64KB. 

Kazu 

--- Quote End ---  

 

 

Yes, CodeSourcery pointed out to me today that the current limit is in fact 32KB because the compiler is not (yet) using a biased GOT pointer on Nios2. I had not been aware of that. (A week ago I wasn't aware of this issue at all. :-)) 

 

Do you have an example program you can share which overruns the GOT? I have the impression that C++ is doing something to generate a lot of globals and overrun the GOT quickly. (http://gcc.gnu.org/wiki/visibility mentions a C++ library with 200000 globals.)  

 

Having a concrete example in hand to reproduce this problem would be helpful.  

 

Possibly we really should be fixing g++ to be more economical about generating globals, instead-of / as-well-as supporting larger GOTs...?
Altera_Forum
Honored Contributor I
51 Views

Hi, 

 

 

--- Quote Start ---  

Do you have an example program you can share which overruns the GOT? I have the impression that C++ is doing something to generate a lot of globals and overrun the GOT quickly. (http://gcc.gnu.org/wiki/visibility mentions a C++ library with 200000 globals.)  

 

--- Quote End ---  

 

 

I encountered this problem when I tried to build GTK programs. Please see 

 

http://www.alterawiki.com/wiki/linux_with_mmu_on_veek/t-pad 

 

. 'tangogps' and its libraries are working with larger GOTs.  

 

Kazu
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