eh_frame unwind info for plt on aarch64

[Indu Bhagat]

Hello,

At this time, ld does not generate EH Frame unwind information for the 
.plt section on aarch64.

The plt[0] entry does do a push to stack:

	stp x16, x30, [sp,#-16]!
	adrp x16, :page: &.got.plt[2]
	ldr x17, [x16, :lo12: &.got.plt[2]]
	add x16, x16, :lo12: &.got.plt[2]
	br x17

I guess an unwinder on aarch64 can potentially attempt to infer cfa, sp, 
lr by "knowing" that it is in a specific instruction in the plt[0], but 
in practice is that what all the unwinders do for plt in aarch64?

Is there interest in generating EH frame unwind information for the .plt 
section on aarch64 by ld (support for --ld-generated-debug-info on 
aarch64) ? I think the support will look similar to the fix for 
https://sourceware.org/bugzilla/show_bug.cgi?id=12570 with hand written 
eh_frame sections for plt*.

Thanks
Indu