Re: port-sh3/49597: swapcontext(3) stack pointer problem on NetBSD/sh3

[Yasushi Oshima <oshima-ya%yagoto-urayama.jp@localhost>]

The following reply was made to PR port-sh3/49597; it has been noted by GNATS.

From: Yasushi Oshima <oshima-ya%yagoto-urayama.jp@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: port-sh3/49597: swapcontext(3) stack pointer problem on
 NetBSD/sh3
Date: Fri, 23 Jan 2015 01:42:39 +0900 (JST)

 Thu, 22 Jan 2015 14:55:00 +0000 (UTC) 
 Valery Ushakov <uwe%stderr.spb.ru@localhost> wrote'
 
 >  Have you tested this?
 
 Yes, but __PIC__ case only. 
 
 The atf-tests in lib/libc/sys/t_swapcontext and fs/psshfs became
 to success by this patch in my environment.
   
 >  From a quick look, getcontext() captures the state that has not two,
 >  but three registers in the stack - including mov.l r4, @-sp in the
 >  delay slot of the CALL, doesn't it?
 
 Yes include in the delay slot, and include in PIC_PROLOGUE() macro.
 
 Stacking register is:
 1) PIC_PROLOGUE(.L_got) ; r12 when __PIC__ only in sh3/asm.h
 2) mov.l r5, @-sp
 3) sts.l pr, @-sp
 4) mov.l r4, @-sp  ; in delay slot (CALL is bsrf or bsr)
 and get from stack after getcontext()
 5) mov.l @sp+ r1
 
 SP saved in a ucontext stored by getcontext() shows 4 regs(__PIC__)
 or 3 regs (NOT __PIC__) away from swapcontext() caller.
 After getcontext() and pop stack by 5), current SP is 3 (or 2) regs away.
 
 And I've checked this difference of SP is 12 bytes (=3 regs) by gdb 
 libc/sys/t_swapcontext test program (in __PIC__ case).
 
 Thanks.