On Fri, Dec 04, 2015 at 02:28:40AM +0000, Trent Piepho wrote: > On Thu, 2015-12-03 at 01:24 +0000, Trent Piepho wrote: > > The asm code to do the actual call into the kernel (or another > > barebox) when compiled in thumb2 mode isn't necessary. gcc generates > > a perfectly good calling sequence from a normal function pointer call. > > If it didn't, the code in bootstrap_boot() that uses a function > > pointer to jump to the 2nd stage barebox from an xloader wouldn't > > work. > > The same commit that originally added this code also added > thumb2_execute(), which is used by the go command in a thumb2 build. > > This doesn't seem necessary for the same reason as the code in > start_linux. THUMB2 selects AEABI, which in turn turns on the aapcs > abi, which requires interworking safe indirect calls. And again, the > bootstrap code doesn't use a special call sequence so if it didn't work > that would be broken too. > > The code for thumb2_execute() is also odd in that it subtracts one from > argc, drops the 1st argv entry, and supplies zero for the first function > argument. I.e., "go" in arm mode (and all non-arm arches) does this: > func(argc - 1, &argv[1]); > and in thumb2 mode does this: > func(0, argc - 2, &argv[2]); > > I don't see why one would want this difference. This is a bug. We want to shift argv[] by one, not by two. I must accidently have done this twice. As you note the thumb2 execution code is unnecessary anyway, we can remove the bug by removing the code. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
