[PATCH] ARM: Remove kernel booting call for thumb2 mode

[Sascha Hauer]

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

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