Re: alpha stack alignment: 8- or 16-byte

[Rin Okuyama <rokuyama.rk%gmail.com@localhost>]

Hi,

On 2021/07/06 6:24, Jason Thorpe wrote:
> > On Jul 5, 2021, at 8:53 AM, Jason Thorpe <thorpej%me.com@localhost> wrote:
> >
> >
> >
> > > On Jul 5, 2021, at 7:09 AM, Rin Okuyama <rokuyama.rk%gmail.com@localhost> wrote:
> > >
> > > (1) Align sp to 8-byte boundary: keep our kernel and libraries as well,
> > >    and fix GCC, or
> > >
> > > (2) Align sp to 16-byte boundary: fix our kernel and libraries.
> >
> > My preference is (2).  The kernel already does this for its own functions in locore.s (look for the functions declared NESTED).
> >
> > This should take care of the kernel portion of the change:
> >
> > 	https://www.netbsd.org/~thorpej/alpha-stack-patch.txt
> >
> > The only libc routine that looks broken to me is swapcontext() (it pushes a 24-byte stack frame).  Do you see any other broken ones?
>
> FYI -- I built an alpha release with the above patch, plus a fix to swapcontext(), with the HACKS removed, and I'm doing an ATF run in Qemu now.

Thank you for your comment and patch for kernel!

In addition to swapcontext(), few more routines should be fixed for
userland. Please find the attached patch.

With your and my patches, at least the system boots multiuser, and
GDB and pkgsrc/devel/gettext-tools work fine. I'm now running ATF.

> (I finally, at long last, have some real Alpha hardware nearly in my possession after many years of lacking it... and an early-ish model, at that, so I should be able to verify on real hardware again very soon...)

Good news! Have fun :)

Thanks,
rin

Index: lib/libc/arch/alpha/gen/__setjmp14.S
===================================================================
RCS file: /home/netbsd/src/lib/libc/arch/alpha/gen/__setjmp14.S,v
retrieving revision 1.8
diff -p -u -r1.8 __setjmp14.S
--- lib/libc/arch/alpha/gen/__setjmp14.S	21 Oct 2020 01:24:05 -0000	1.8
+++ lib/libc/arch/alpha/gen/__setjmp14.S	5 Jul 2021 22:24:01 -0000
@@ -68,12 +68,12 @@ LEAF(__setjmp14, 1)
 	lda	a2, SC_MASK(s0)			/* point to mask in sc */
 	CALL(__sigprocmask14)
 
-	lda	sp, -24(sp)			/* sizeof struct sigaltstack */
+	lda	sp, -32(sp)	/* roundup(sizeof(struct sigaltstack), 16) */
 	mov	zero, a0
 	mov	sp, a1
 	CALL(__sigaltstack14)
 	ldl	t0, 16(sp)			/* offset of ss_flags */
-	lda	sp, 24(sp)			/* sizeof struct sigaltstack */
+	lda	sp, 32(sp)			/* see above */
 	ldq	ra, (SC_REGS+_REG_RA*8)(s0)	/* restore return address */
 	blt	v0, botch			/* check for error */
 	and	t0, 0x1, t0			/* get SA_ONSTACK flag */
Index: lib/libc/arch/alpha/gen/_lwp.c
===================================================================
RCS file: /home/netbsd/src/lib/libc/arch/alpha/gen/_lwp.c,v
retrieving revision 1.7
diff -p -u -r1.7 _lwp.c
--- lib/libc/arch/alpha/gen/_lwp.c	12 Sep 2012 14:13:43 -0000	1.7
+++ lib/libc/arch/alpha/gen/_lwp.c	5 Jul 2021 22:25:36 -0000
@@ -58,7 +58,7 @@ _lwp_makecontext(ucontext_t *u, void (*s
 	gr[_REG_T12] = (unsigned long) start;
 	gr[_REG_RA] = (unsigned long) _lwp_exit;
 	gr[_REG_A0] = (unsigned long) arg;
-	gr[_REG_SP] = ((unsigned long) (stack_base + stack_size)) & ~0x7;
+	gr[_REG_SP] = ((unsigned long) (stack_base + stack_size)) & ~0xf;
 	gr[_REG_S6] = 0;
 	gr[_REG_UNIQUE] = (unsigned long)private;
 
Index: lib/libc/arch/alpha/gen/makecontext.c
===================================================================
RCS file: /home/netbsd/src/lib/libc/arch/alpha/gen/makecontext.c,v
retrieving revision 1.6
diff -p -u -r1.6 makecontext.c
--- lib/libc/arch/alpha/gen/makecontext.c	20 Sep 2011 08:42:29 -0000	1.6
+++ lib/libc/arch/alpha/gen/makecontext.c	5 Jul 2021 22:30:34 -0000
@@ -51,12 +51,14 @@ makecontext(ucontext_t *ucp, void (*func
 	unsigned long *sp;
 	va_list ap;
 
-	/* Compute and align stack pointer. */
+	/* Compute stack pointer. */
 	sp = (unsigned long *)
-	    (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x7);
+	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
 	/* Allocate necessary stack space for arguments exceeding a0-5. */
 	if (argc > 6)
 		sp -= (argc - 6);
+	/* Align stack pointer. */
+	sp = (unsigned long *)((uintptr_t)sp & ~0xf);
 	gr[_REG_SP] = (__greg_t)sp;
 	/* Arrange for return via the trampoline code. */
 	gr[_REG_RA] = (__greg_t)__resumecontext;
Index: lib/libc/arch/alpha/gen/swapcontext.S
===================================================================
RCS file: /home/netbsd/src/lib/libc/arch/alpha/gen/swapcontext.S,v
retrieving revision 1.4
diff -p -u -r1.4 swapcontext.S
--- lib/libc/arch/alpha/gen/swapcontext.S	21 Oct 2020 01:24:05 -0000	1.4
+++ lib/libc/arch/alpha/gen/swapcontext.S	5 Jul 2021 22:45:51 -0000
@@ -34,23 +34,23 @@
 
 NESTED(swapcontext, 2, 24, ra, IM_RA|IM_A0|IM_A1, 0)
 	LDGP(pv)
-	lda	sp, -24(sp)
-	stq	ra, (24- 8)(sp)		/* must save ra, oucp, ucp */
-	stq	a0, (24-16)(sp)
-	stq	a1, (24-24)(sp)
+	lda	sp, -32(sp)
+	stq	ra, (32- 8)(sp)		/* must save ra, oucp, ucp */
+	stq	a0, (32-16)(sp)
+	stq	a1, (32-24)(sp)
 	CALL(_getcontext)		/* getcontext(oucp) */
-	ldq	t0, (24-16)(sp)
+	ldq	t0, (32-16)(sp)
 	bne	v0, Lerr
-	ldq	t1, (24- 8)(sp)
+	ldq	t1, (32- 8)(sp)
 	stq	t1, (UC_GREGS + _REG_RA*8)(t0)	/* Adjust saved RA */
 	stq	t1, (UC_GREGS + _REG_PC*8)(t0)	/* Adjust saved PC */
-	lda	t1, 24(sp)
+	lda	t1, 32(sp)
 	stq	t1, (UC_GREGS + _REG_SP*8)(t0)	/* Adjust saved SP */
 
-	ldq	a0, (24-24)(sp)
+	ldq	a0, (32-24)(sp)
 	CALL(setcontext)		/* setcontext(ucp) */
 Lerr:
-	ldq	ra, (24- 8)(sp)
-	lda	sp, 24(sp)
+	ldq	ra, (32- 8)(sp)
+	lda	sp, 32(sp)
 	RET
 END(swapcontext)
Index: lib/libm/arch/alpha/lrint.S
===================================================================
RCS file: /home/netbsd/src/lib/libm/arch/alpha/lrint.S,v
retrieving revision 1.3
diff -p -u -r1.3 lrint.S
--- lib/libm/arch/alpha/lrint.S	13 Oct 2004 15:18:31 -0000	1.3
+++ lib/libm/arch/alpha/lrint.S	5 Jul 2021 22:37:32 -0000
@@ -12,10 +12,10 @@ LEAF(lrint, 1)
 #if 0
 	ftoit ft0,v0
 #else
-	lda sp,-8(sp)
+	lda sp,-16(sp)
 	stt ft0,0(sp)
 	ldq v0,0(sp)
-	lda sp,8(sp)
+	lda sp,16(sp)
 #endif
 	ret
 END(lrint)