Re: [Ltt-dev] Linux Kernel Markers : sparc build issue
Mathieu Desnoyers <[email protected]>
| Newsgroups | gmane.linux.ports.sparc,gmane.linux.kernel.tracing |
|---|---|
| Message-ID | <20070207184639.GA14299@Krystal> |
This issue is "fixed" by disabling KALLSYMS when building the kernel. I
added the following information in the menus :
config MARKERS
bool "Activate markers"
select MODULES
default n
help
Place an empty function call at each marker site. Can be
dynamically changed for a probe function.
Note that on sparc32, m68k and RS/6000, you may have to disable
kallsyms (under Configure standard kernel features (for small
systems), "Load all symbols for debugging/ksymoops") because of
a GOT size limit of respectively : 8k, 32k and 32k. It can
otherwise cause linking errors when too much markers appear in
the code.
Mathieu
* Mathieu Desnoyers ([email protected]) wrote:
> It seems like I bust the 8k limit for the sparc GOT :
>
> The kallsyms_addresses is 8614 lines long (for a 33.6kB total) in the .S,
> and, according to
> http://gcc.gnu.org/onlinedocs/gcc-4.1.1/gcc/Code-Gen-Options.html :
>
> "If the GOT size for the linked executable exceeds a machine-specific
> maximum size, you get an error message from the linker indicating that
> -fpic does not work; in that case, recompile with -fPIC instead. (These
> maximums are 8k on the SPARC and 32k on the m68k and RS/6000. The 386
> has no such limit.)"
>
> Mathieu
>
>
> * Mathieu Desnoyers ([email protected]) wrote:
> > * Frank Ch. Eigler ([email protected]) wrote:
> > >
> > > Perhaps you could post excerpts of "objdump -dr <file.o>", to see the
> > > disassembly / relocations in question.
> > >
> > > - FChE
> >
> > Hi Frank,
> >
> > (this message follow up on
> > http://listserv.shafik.org/pipermail/ltt-dev/2007-February/002212.html)
> >
> > compudj@amd64:~/obj/sparc$ PATH=/opt/crosstool/gcc-4.1.1-glibc-2.3.6/sparc-unknown-linux-gnu/bin sparc-unknown-linux-gnu-objdump -dr .tmp_kallsyms3.o
> >
> > .tmp_kallsyms3.o: file format elf32-sparc
> >
> > (that's all)
> >
> > By looking at what follows in more depth, it looks like the symbols I
> > keep are relative to the beginning of the _text section and sparc would
> > have a limit regarding this (maximum offset ? number of offsets relative
> > to a symbol ?)
> >
> > Any insights are welcome,
> >
> > Mathieu
> >
> >
> > link error :
> >
> > opt/crosstool/gcc-4.1.1-glibc-2.3.6/sparc-unknown-linux-gnu/bin/sparc-unknown-linux-gnu-ld -m elf32_sparc -T arch/sparc/kernel/vmlinux.lds arch/sparc/kernel/head.o arch/sparc/kernel/init_task.o init/built-in.o --start-group usr/built-in.o arch/sparc/kernel/built-in.o arch/sparc/mm/built-in.o arch/sparc/math-emu/built-in.o kernel/built-in.o mm/built-in.o fs/built-in.o ipc/built-in.o security/built-in.o crypto/built-in.o block/built-in.o lib/lib.a arch/sparc/prom/lib.a arch/sparc/lib/lib.a lib/built-in.o arch/sparc/prom/built-in.o arch/sparc/lib/built-in.o drivers/built-in.o sound/built-in.o net/built-in.o --end-group .tmp_kallsyms3.o arch/sparc/boot/btfix.o -o arch/sparc/boot/image
> > .tmp_kallsyms3.o: In function `kallsyms_addresses':
> > .tmp_kallsyms3.S:(.rodata+0x0): relocation truncated to fit: R_SPARC_32 against symbol `_text' defined in .text section in arch/sparc/boot/image
> > .tmp_kallsyms3.S:(.rodata+0x8): relocation truncated to fit: R_SPARC_32 against symbol `_text' defined in .text section in arch/sparc/boot/image
> > ...
> > .tmp_kallsyms3.S:(.rodata+0x2c): additional relocation overflows omitted
> > from the output
> > make[2]: *** [arch/sparc/boot/image] Error 1
> >
> >
> > arch/sparc/kernel/vmlinux.lds
> > ...
> > OUTPUT_FORMAT("elf32-sparc", "elf32-sparc", "elf32-sparc")
> > OUTPUT_ARCH(sparc)
> > ENTRY(_start)
> > jiffies = jiffies_64 + 4;
> > SECTIONS
> > {
> > . = 0x10000 + SIZEOF_HEADERS;
> > .text 0xf0004000 :
> > {
> > _text = .;
> > *(.text)
> > . = ALIGN(8); __sched_text_start = .; *(.sched.text) __sched_text_end = .;
> > . = ALIGN(8); __lock_text_start = .; *(.spinlock.text) __lock_text_end = .;
> > *(.gnu.warning)
> > } =0
> > _etext = .;
> > ...
> >
> >
> > A look at .tmp_kallsyms3.S, symbol kallsyms_addresses which seems to cause
> > linking error on sparc :
> >
> >
> > #include <asm/types.h>
> > #if BITS_PER_LONG == 64
> > #define PTR .quad
> > #define ALGN .align 8
> > #else
> > #define PTR .long
> > #define ALGN .align 4
> > #endif
> > .section .rodata, "a"
> > .globl kallsyms_addresses
> > ALGN
> > kallsyms_addresses:
> > PTR _text - 0xeffd7000
> > PTR 0x2d000
> > PTR _text - 0xeffd6fb8
> > PTR _text - 0xeffd6f50
> > PTR _text - 0xeffd6ed0
> > PTR _text - 0xeffd6eac
> > PTR _text - 0xeffd6b84
> > PTR _text - 0xeffd6860
> > PTR _text - 0xeffd6830
> > PTR _text - 0xeffd6814
> > PTR _text - 0xeffd6794
> > PTR _text - 0xeffd6788
> > PTR _text - 0xeffd6778
> > PTR _text - 0xeffd6764
> > PTR _text - 0xeffd673c
> > PTR _text - 0xeffd6714
> > PTR _text - 0xeffd66e4
> > PTR _text - 0xeffd66b4
> > PTR _text - 0xeffd66ac
> > PTR _text - 0xeffd6698
> > PTR _text - 0xeffd6674
> > PTR _text - 0xeffd6650
> > PTR _text - 0xeffd63dc
> > PTR _text - 0xeffd637c
> > PTR _text - 0xeffd6304
> > PTR _text - 0xeffd6060
> > PTR _text - 0xeffd6034
> > PTR _text - 0xeffd6008
> > PTR _text - 0xeffd5ff8
> > .....
> >
> > PTR _text - 0xeffbc7a0
> > PTR _text - 0xeffbc730
> > PTR 0x47930
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0
> > PTR _text + 0x10
> > PTR _text + 0x20
> > PTR _text + 0x30
> > PTR _text + 0x40
> > PTR _text + 0x50
> > PTR _text + 0x60
> > PTR _text + 0x70
> > PTR _text + 0x80
> > PTR _text + 0x90
> > PTR _text + 0xa0
> > PTR _text + 0xb0
> > PTR _text + 0xc0
> > PTR _text + 0x110
> > PTR _text + 0x120
> > PTR _text + 0x130
> > PTR _text + 0x140
> > PTR _text + 0x150
> > ....
> >
> >
> > PTR _text + 0x1b67c4
> > PTR _text + 0x1b67d8
> > PTR 0xf01ba890
> >
> >
> > And by the way, I also add my own section to
> > include/asm-generic/vmlinux.lds.h in RODATA :
> > adds at line 124, kernel 2.6.20 :
> > /* Kernel markers : pointers */ \
> > .markers : AT(ADDR(.markers) - LOAD_OFFSET) { \
> > VMLINUX_SYMBOL(__start___markers) = .; \
> > *(.markers) \
> > VMLINUX_SYMBOL(__stop___markers) = .; \
> > } \
> >
> >
> >
> > --
> > Mathieu Desnoyers
> > Computer Engineering Graduate Student, École Polytechnique de Montréal
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
> > _______________________________________________
> > Ltt-dev mailing list
> > [email protected]
> > http://listserv.shafik.org/mailman/listinfo/ltt-dev
> >
>
> --
> Mathieu Desnoyers
> Computer Engineering Graduate Student, École Polytechnique de Montréal
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
> _______________________________________________
> Ltt-dev mailing list
> [email protected]
> http://listserv.shafik.org/mailman/listinfo/ltt-dev
>
--
Mathieu Desnoyers
Computer Engineering Graduate Student, École Polytechnique de Montréal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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