Am 25.12.2017 um 19:37 schrieb Antony Pavlov:
> How to repropduce the unaligned store problem
>
> qemu-system-mips -nodefaults -M malta -m 256 \
> -nographic -serial stdio -monitor null \
> -bios barebox-flash-image \
> -net user -net nic,model=rtl8139
>
> ...
>
> barebox:/ dhcp
>
> Ooops, address error on store!
>
> $ 0 : 00000000 00000000 01010600 697f2a2e
> $ 4 : a0850000 00000000 0000001c a040c1b8
> $ 8 : 00000000 00000002 00000002 00000000
> $12 : 00000000 00000040 00000100 00000001
> $16 : a040bba0 a0850000 a0850000 a0850000
> $20 : 00000000 00000075 00000076 a040ba20
> $24 : 00000002 a080f210
> $28 : 00000000 a03ffce0 fffffffd a0833b8c
> Hi : 000154f8
> Lo : 20000000
> epc : a0833b84
> ra : a0833b8c
> Status: 00000002
> Cause : 80000414
> Config: 80008482
>
> ### ERROR ### Please RESET the board ###
>
> The unaligned store instruction is located in the bootp_request() from net/dhcp.c:
>
> a0833b50 <bootp_request>:
> ..
> a0833b7c: 3c020101 lui v0,0x101
> a0833b80: 24420600 addiu v0,v0,1536 /* 0x1010600 -> v0 */
> a0833b84: 0c20024a jal a0800928 <get_time_ns>
> a0833b88: ae02002a sw v0,42(s0) /* store 0x1010600 to addr s0 + 42 */
>
> This assembler code is generated by mips-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> from this:
>
> bp = (struct bootp *)payload;
> bp->bp_op = OP_BOOTREQUEST; /* 0x01 */
> bp->bp_htype = HWT_ETHER; /* 0x01 */
> bp->bp_hlen = HWL_ETHER; /* 0x06 */
> bp->bp_hops = 0;
>
> Compiler replaces four 'store byte' instruction by one 'store 32-bit word'
> instruction. Alas sometimes this leads to unaligned store situation.
>
> Making struct bootp __packed prevents this optimization and fixes the problem.
>
> Signed-off-by: Antony Pavlov <antonynpavlov@xxxxxxxxx>
Tested-by: Oleksij Rempel <linux@xxxxxxxxxxxxxxxx>
This patch solves similar crash on Atheros AR9331.
> ---
> net/dhcp.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/dhcp.c b/net/dhcp.c
> index c5386fe942..4177220410 100644
> --- a/net/dhcp.c
> +++ b/net/dhcp.c
> @@ -45,7 +45,7 @@ struct bootp {
> char bp_sname[64]; /* Server host name */
> char bp_file[128]; /* Boot file name */
> char bp_vend[0]; /* Vendor information */
> -};
> +} __packed;
>
> /* DHCP States */
> typedef enum {
>
--
Regards,
Oleksij
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