George G. Davis wrote: > On Fri, May 15, 2009 at 02:55:57PM +0100, Ben Dooks wrote: > > On Fri, May 15, 2009 at 02:51:05PM +0100, Jamie Lokier wrote: > > > Eek, can you say a bit more about the ARM EABI mismatch? > > > > > > I would like to run a shiny modern ARM EABI kernel and userspace, but > > > also need to run one or two OABI binaries (from the gcc 2.95 era) on > > > the same kernel which I cannot recompile because they're built with > > > closed source libraries only supplied as OABI. > > > > > > Does that not work at all? > > > > There are a few ioctl() incompatibilities between the two ABIs, the > > main problems are within the ALSA API. Mostly it will work, but there > > are a couple of caveats. > > Right, you can run ARM OABI binaries on an ARM eABI kernel by enabling > OABI_COMPAT. However, as Ben notes, there are (more than, IMNSHO ; ) > "a couple of caveats". Most of the "easy" ABI compatibility fixups > should be handled already via OABI_COMPAT. However, it's practically > impossible to fixup all OABI/eABI compatibility issues due to register > assignment, parameter alignment and/or packing differences between > the two ABIs. You would have to analyze all kernel and driver > user interfaces to reassign parameters to registers, align and/or > repack data structures, etc.,. In fact, some of the existing fixups > include side effects that in some cases can cause userspace code to > fail, depending on how it is using I/O parameters, e.g. in some cases, > library code may try to validate parameters which are relocated and > those tests fail due to reshuffling of parameters. It's a nasty > path to go down, quite frankly. I would not recommend trying to > support OABI binaries on an eABI kernel using OABI_COMPAT.
Structure packing: Isn't that basically the same set of fixups that need to be done for 32-bit compatibility on 64-bit kernels? Could it even use the same code - sneakily replacing "32" with OABI and "64" with EABI? Register/parameter assignment: How is that relevant to the kernel interface, if the kernel itself and modules are all EABI? The system call interface is a fixed set of registers. It sounds like you're saying I should use OABI kernels and userspace even with latest kernels, if I have a single OABI binary that might use anything interesting from the kernel, like readdir, poll, signal context, ioctl, device read/write, or any other system calls which take a struct that isn't all 32-bit words. -- Jamie -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
