Re: linker bug?
On Sun, 30 Nov 2003, Geert Uytterhoeven wrote:
> When trying to get modules working in 2.6.0-test11, I'm seeing something weird.
> A kernel without module support boots fine, while a kernel with module support
> crashes very early because any Chip RAM allocation fails.
> Some investigation shows that amiga_hw_present.CHIP_RAM is set initially, but
> looses its value later. Apparently it's destroyed when mach_gettimeoffset is
> filled in.
> System.map shows:
> | 00180bf2 B amiga_hw_present
> | 00180bf4 B mach_gettimeoffset
> I.e. amiga_hw_present is only 16 bits large, while it contains a bitfield of 32
> single bit values. So when mach_gettimeoffset is changed, half of
> amiga_hw_present is overwritten.
> I'm using cross gcc version 2.95.2 20000220 and cross binutils version 2.9.5
> (with BFD 188.8.131.52.37), both built from Debian sources a while ago.
> Then I relinked the kernel using my newer cross binutils (184.108.40.206.10
> 20021010, from Debian toolchain-source). System.map stills shows that
> amiga_hw_present is only 2 bytes large.
> Then I recompiled arch/m68k/amiga/config.c using my newer cross gcc (3.2, from
> Debian toolchain-source) and relinked (tried both binutils). System.map stills
> shows that amiga_hw_present is only 2 bytes large.
> `nm -S arch/m68k/amiga/config.o' does show that amiga_hw_present has a size of
> 4 bytes in all cases, so it looks like a linker bug.
> Anyone seen a similar problem before?
Whatever linker[*] I use to link the final image, `nm -S vmlinux | sort' shows
| 0017f620 00000004 B m68k_memoffset *
| 0017f621 00000001 B amiga_psfreq
| 0017f622 00000004 B amiga_hw_present *
| 0017f624 00000004 B mach_gettimeoffset *
| 0017f626 00000070 b ram_resource *
| 0017f628 00000004 B mach_reset
| 0017f62c 00000100 b m68k_command_line *
| 0017f674 000007d0 b nodes *
| 0017f696 00000002 b jiffy_ticks
| 0017f698 00000038 b ami_irq_list
| 0017f6d0 00000040 b ami_ablecount
| 0017f710 00000004 B amiga_chip_size
As you can see, several objects (marked with an asterisk) are allocated less
memory than their size indicates.
[*] I tried 2.9.5, 220.127.116.11.10, 18.104.22.168.4 (all cross) and 22.214.171.124.7
(native). All fail.
If CONFIG_MODULES is not set, everything is OK (well, the kernel boots, and a
quick look didn't reveal any too-small objects).
Who should I bug with this problem? All binutils are from Debian (or compiled
from Debian sources).
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- firstname.lastname@example.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds