O64 may not be supported ABI, but it provides us with a feature that is
specifically, it generates 32 bit symbol addresses instead of 64 bit
ones. This cuts
down on code size considerably. If this feature was implemented in
toolchain as separate
switch, O64 hack could go away.
With that said, you are of course right - IP32 code and some drivers are
they do rely on this feature in many places.
This also means - for a user it isn't recommended to use ElF64 kernel ;-)
Maciej W. Rozycki wrote:
On Fri, 11 Feb 2005, Stephen P. Becker wrote:
First, there's something wrong with "make ip32_defconfig" which generate
config file with "Kernel code model = 64-bit kernel" (MIPS64=y) but
doesn't preselect "Use 64-bit ELF format for building" (BUILD_ELF64=n)
doing so, "make" quickly generates an error:
O2 doesn't use 64-bit ELF format. You have to use o64. See the
O64 isn't a supported ABI for Linux. It's a crazy ad-hoc hack that
shouldn't be used at all. Code to handle it somehow may still exist in
binutils, but it's abandoned -- nobody bothers checking if it still works.
With the upcoming explicit reloc support for non-PIC code in GCC 4.0 it
won't work at all anymore.
arch/mips/Makefile portion of http://dev.gentoo.org/~geoman/cvs.diff for the
proper changes. I'm willing to bet a lot of your problems will go away if you
stop using ELF64. Such a kernel will boot, but it never quite works right.
If you have a problem with n64 binaries, then either you have broken
tools or there is a bug in the platform-dependent code somewhere --
probably some inline asm forgetting about the %higher and %highest
relocations. Check your tools (I'd recommend GCC 3.4.3 and binutils 2.15)
and if they're fine, then file a bug report. N64 binaries work for
several platforms (I've tested three myself; I'm sure others did that
for others as well).
Regardless of the format used for building, the final executable is
converted to ELF32 or ELF64 if necessary to suit the bootloader used, as
controlled by the CONFIG_BOOT_ELF32 and CONFIG_BOOT_ELF64 options.
Ilya A. Volynets-Evenbakh
Total Knowledge. CTO