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authorAntony Pavlov <antonynpavlov@gmail.com>2017-12-25 21:37:58 +0300
committerSascha Hauer <s.hauer@pengutronix.de>2018-01-05 15:52:51 +0100
commit896894088e7de081caddb5fc8dc653bc0f5ac7bb (patch)
tree1b1569df38d6c66da5f646e3677271284b65a3ff /defaultenv
parent55f5907c3ca00bfa36015e162926b62ff8ce0243 (diff)
downloadbarebox-896894088e7de081caddb5fc8dc653bc0f5ac7bb.tar.gz
net: make struct bootp __packed to prevent unaligned store on MIPS
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@gmail.com> Tested-by: Oleksij Rempel <linux@rempel-privat.de> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
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