net: make struct bootp __packed to prevent unaligned store on MIPS
PATCH 1/1 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.
--- net/dhcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
net/dhcp.c +1 -1
@@ -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 {
Signature · 7 lines
2.15.0 _______________________________________________ barebox mailing list [email protected] http://lists.infradead.org/mailman/listinfo/barebox
Am 25.12.2017 um 19:37 schrieb Antony Pavlov:
Quoted 49 lines
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()fromnet/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;
Quoted 6 lines
Compiler replaces four 'store byte' instruction by one 'store 32-bit word' instruction. Alas sometimes this leads to unaligned store situation.
Making struct bootp
__packedprevents this optimization and fixes the problem.Signed-off-by Antony Pavlov <[email protected]>
This patch solves similar crash on Atheros AR9331.
Quoted 18 lines
--- net/dhcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)net/dhcp.c +1
-1@@ -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 {
Signature · 2 lines
Regards, Oleksij
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Sascha Hauer
AppliedQuoted 49 lines · 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()fromnet/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;
Quoted 6 lines
Compiler replaces four 'store byte' instruction by one 'store 32-bit word' instruction. Alas sometimes this leads to unaligned store situation.
Making struct bootp
__packedprevents this optimization and fixes the problem.Signed-off-by Antony Pavlov <[email protected]>
Applied to master, thanks
Sascha
Signature · 9 lines
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