Date: Wed, 7 Sep 2016 01:46:42 -0500 From: Erik Moe <e.moe@rcn.com> To: freebsd-arm <freebsd-arm@freebsd.org> Subject: Unaligned access in ubldr.bin Message-ID: <E04431D8-F38C-4B9F-BFE1-1207265DED8B@rcn.com>
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Hello,
I=E2=80=99ve been trying to bring up FreeBSD on the USB Armory based on =
the i.MX53. I=E2=80=99ve made myself a u-boot patch that will load and =
start ubldr.bin but I=E2=80=99m running into a issue with what I think =
is an unaligned access issue:
## Starting application at 0x70800000 ...
data abort
pc : [<70824bac>] lr : [<7081846c>]
sp : 8f550c98 ip : 70835a00 fp : 8f550cb0
r10: 00000002 r9 : 70838d58 r8 : 70833cd9
r7 : 707fff08 r6 : 000054f0 r5 : 70833cd9 r4 : 00000000
r3 : 70828fc4 r2 : 70833cd9 r1 : 00000001 r0 : 7083705c
Flags: Nzcv IRQs off FIQs off Mode SVC_32
Resetting CPU ...
I=E2=80=99ve hand dissambled the code at pc=3D0x70824bac:
0x70824ba8: 0xe59f21d0 ldr r2, [pc, #464]
0x70824bac: 0xe5825000 str r5, [r2]
0x70824bb0: 0xe5d53000 ldrb r3, [r5]
0x70824bb4: 0xe353002d cmp r3, #45
0x70824bb8: 0x1a00000b bne #+44
The offending instructions is "str r5, [r2]=E2=80=9D where r2 =3D =
0x70833cd9, which sort of makes sense since it isn=E2=80=99t aligned on =
a 4 byte boundary. I=E2=80=99m new to arm ARM, so I=E2=80=99m not =
really sure. My questions are these:
1.) Doesn=E2=80=99t ARMv6 and higher architecture allow unaligned =
access? Is there something that u-boot needs be doing in initialization =
to allow unaligned access?
2.) Does ubldr make the assumption that unaligned access is allowed and =
maybe shouldn=E2=80=99t? I would think not since ubldr has been around =
for a while and works on numerous ARM processors.
Any thoughts at which direction to investigate would be appreciated.
Thanks,
Erik
FYI, ubldr is failing in =E2=80=9Cgetopt=E2=80=9D. I=E2=80=99ve used =
objdump to disassemble ubldr.bin. You=E2=80=99ll have to subtract the =
offset 0xf8 and add 0x7080000 to the addresses bellow to get them to =
align with the addresses above.
getopt(int nargc, char * const *nargv, const char *ostr)
{
24c4c: e92d4df0 push {r4, r5, r6, r7, r8, sl, fp, lr}
24c50: e28db018 add fp, sp, #24
24c54: e1a07000 mov r7, r0
static char *place =3D EMSG; /* option letter =
processing */
char *oli; /* option letter list =
index */
if (optreset || !*place) { /* update scanning =
pointer */
24c58: e59f0214 ldr r0, [pc, #532] ; 24e74 =
<getopt+0x228>
24c5c: e1a06001 mov r6, r1
24c60: e1a08002 mov r8, r2
24c64: e5901000 ldr r1, [r0]
24c68: e3510000 cmp r1, #0
24c6c: 1a000004 bne 24c84 <getopt+0x38>
24c70: e59f1200 ldr r1, [pc, #512] ; 24e78 =
<getopt+0x22c>
24c74: e5913000 ldr r3, [r1]
24c78: e5d34000 ldrb r4, [r3]
24c7c: e3540000 cmp r4, #0
24c80: 1a00001d bne 24cfc <getopt+0xb0>
24c84: e3a01000 mov r1, #0
optreset =3D 0;
24c88: e5801000 str r1, [r0]
if (optind >=3D nargc || *(place =3D nargv[optind]) !=3D =
'-') {
place =3D EMSG;
return (-1);
}
if (place[1] && *++place =3D=3D '-') { /* found =
"--" */
++optind;
24c8c: e59f01e8 ldr r0, [pc, #488] ; 24e7c =
<getopt+0x230>
24c90: e5901000 ldr r1, [r0]
static char *place =3D EMSG; /* option letter =
processing */
char *oli; /* option letter list =
index */
if (optreset || !*place) { /* update scanning =
pointer */
optreset =3D 0;
if (optind >=3D nargc || *(place =3D nargv[optind]) !=3D =
'-') {
24c94: e1510007 cmp r1, r7
24c98: aa000011 bge 24ce4 <getopt+0x98>
24c9c: e7965101 ldr r5, [r6, r1, lsl #2]
24ca0: e59f21d0 ldr r2, [pc, #464] ; 24e78 =
<getopt+0x22c>
24ca4: e5825000 str r5, [r2]
24ca8: e5d53000 ldrb r3, [r5]
24cac: e353002d cmp r3, #45 ; 0x2d
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