[src/trunk]: src/sys/arch/aarch64/aarch64 Align the loaded kernel image to 2M...

[ryo <ryo%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0e2885746a60
branches:  trunk
changeset: 369601:0e2885746a60
user:      ryo <ryo%NetBSD.org@localhost>
date:      Tue Aug 23 05:29:44 2022 +0000

description:
Align the loaded kernel image to 2Mbytes, if necessary.

It appears that there are bootloaders that cannot specify the load address or ignore it.

diffstat:

 sys/arch/aarch64/aarch64/start.S |  39 +++++++++++++++++++++++++++++++++++++--
 1 files changed, 37 insertions(+), 2 deletions(-)

diffs (65 lines):

diff -r 698be8c5923b -r 0e2885746a60 sys/arch/aarch64/aarch64/start.S
--- a/sys/arch/aarch64/aarch64/start.S  Tue Aug 23 01:08:04 2022 +0000
+++ b/sys/arch/aarch64/aarch64/start.S  Tue Aug 23 05:29:44 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: start.S,v 1.11 2020/09/15 09:28:20 ryo Exp $   */
+/*     $NetBSD: start.S,v 1.12 2022/08/23 05:29:44 ryo Exp $   */
 
 /*
  * Copyright (c) 2017 Ryo Shimizu <ryo%nerv.org@localhost>
@@ -33,12 +33,13 @@
 #include <aarch64/asm.h>
 #include "assym.h"
 
-RCSID("$NetBSD: start.S,v 1.11 2020/09/15 09:28:20 ryo Exp $")
+RCSID("$NetBSD: start.S,v 1.12 2022/08/23 05:29:44 ryo Exp $")
 
 /*
  * Padding at start of kernel image to make room for 64-byte header
  * (non-ELF booting)
  */
+.header:
        .space  64, 0x0
 
 /*
@@ -46,6 +47,40 @@
  */
        .global start
 start:
+       /* DON'T CLOBBER X0-X3 REGISTERS. THEY ARE UBOOT ARGUMENTS */
+
+       /*
+        * Relocate to L2_SIZE(2Mbyte) align if necessary
+        *
+        * x8 = currently loaded address
+        * x9 = (x8 + L2_SIZE - 1) & -L2_SIZE = new (aligned) loaded address
+        */
+       adrl    x8, .header
+       mov     x9, #(L2_SIZE-1)
+       add     x9, x9, x8
+       and     x9, x9, #-L2_SIZE
+       cmp     x8, x9
+       b.eq    9f
+
+       /* x10 = size = (_edata - __kernel_text) */
+       adrl    x10, _edata
+       adrl    x11, __kernel_text
+       sub     x10, x10, x11
+
+       /* do memmove(x9, x8, x10) */
+       add     x8, x8, x10
+       add     x13, x9, x10
+1:
+       ldp     x11, x12, [x8, #-16]!
+       stp     x11, x12, [x13, #-16]!
+       cmp     x13, x9
+       b.hi    1b
+
+       /* jump to new (aligned) loaded address */
+       add     x9, x9, #(start - .header)      /* skip header */
+       br      x9
+9:
+
        mrs     x8, CurrentEL
        lsr     x8, x8, #2
        cmp     x8, #0x2