From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-lf0-x243.google.com ([2a00:1450:4010:c07::243]) by bombadil.infradead.org with esmtps (Exim 4.89 #1 (Red Hat Linux)) id 1eTXdf-0007tV-D3 for barebox@lists.infradead.org; Mon, 25 Dec 2017 18:38:19 +0000 Received: by mail-lf0-x243.google.com with SMTP id u84so18052198lff.7 for ; Mon, 25 Dec 2017 10:38:04 -0800 (PST) From: Antony Pavlov Date: Mon, 25 Dec 2017 21:37:58 +0300 Message-Id: <20171225183758.7773-1-antonynpavlov@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: [PATCH] net: make struct bootp __packed to prevent unaligned store on MIPS To: barebox@lists.infradead.org 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 : .. a0833b7c: 3c020101 lui v0,0x101 a0833b80: 24420600 addiu v0,v0,1536 /* 0x1010600 -> v0 */ a0833b84: 0c20024a jal a0800928 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 --- 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 { -- 2.15.0 _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox