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Subjectusing objdump to debug some n/w code in kernel
Hi,

I am using the 'makelst' script in the scripts directory to generate
interleaved source code and assembly listing. This script uses 'objdump'

Now my problem is that the original C code and the .lst files dont seem to
match. They are listed below.

I get an oops with EIP at c01b3230. But the corresponding C code for that
(switch (n % 4)) isnt written by me!! In other words the instructions
between c01b3223 - c01b3232 dont seem to make sense.

Can anybody throw any light on this 'phenomena' ?
BTW, the string ': "memory");' seems to be repeating in a lot of
places in the .lst file. Is there something about objdump that i havent
read up on.

Regards,
Amit

Original code:
-------------
/* .......
So host > network > gateway entries.
*/
for (i=0; i < MAX_ROUTING_ENTRIES; i++)
{
/* copy the routing entry into our local variable..just to be safe
We will optimize later by doing without this copy */
memcpy(&tmp_entry, ptr_route, sizeof(struct routing_entry));

switch(tmp_entry.rt_flag)
{
case 'H':
/* if dest ip is a host entry */
----- end original code -----------------

Code generated using 'makelst:
-------------------------------
/* ....
So host > network > gateway entries.
*/
for (i=0; i < MAX_ROUTING_ENTRIES; i++)
c01b3206: 31 ed xor %ebp,%ebp
c01b3208: 8d 5c 24 48 lea 0x48(%esp,1),%ebx
c01b320c: 8d 54 24 68 lea 0x68(%esp,1),%edx
c01b3210: 8b 49 5c mov 0x5c(%ecx),%ecx
c01b3213: 89 4c 24 18 mov %ecx,0x18(%esp,1)
c01b3217: 89 54 24 10 mov %edx,0x10(%esp,1)
c01b321b: 8d 4c 24 28 lea 0x28(%esp,1),%ecx
c01b321f: 89 4c 24 14 mov %ecx,0x14(%esp,1)
c01b3223: 90 nop
: "memory");
{
int d0, d1, d2;
switch (n % 4) {
case 0: COMMON(""); return to;
c01b3224: b9 08 00 00 00 mov $0x8,%ecx
c01b3229: 89 df mov %ebx,%edi
c01b322b: 8b 74 24 18 mov 0x18(%esp,1),%esi
c01b322f: fc cld
c01b3230: f3 a5 repz movsl %ds:(%esi),%es:(%edi)
{
/* copy the routing entry into our local variable..just to be safe
We will optimize later by doing without this copy */
memcpy(&tmp_entry, ptr_route, sizeof(struct routing_entry));

switch(tmp_entry.rt_flag)
c01b3232: 8a 44 24 54 mov 0x54(%esp,1),%al
c01b3236: 3c 48 cmp $0x48,%al
c01b3238: 74 1a je c01b3254
<veth_route_lookup+0xa8>c01b323a: 7f 0c jg
c01b3248 <veth_route_lookup+0x9c>c01b323c: 3c 47
cmp $0x47,%al
c01b323e: 74 60 je c01b32a0
<veth_route_lookup+0xf4>c01b3240: e9 d9 00 00 00 jmp
c01b331e <veth_route_lookup+0x172>
c01b3245: 8d 76 00 lea 0x0(%esi),%esi
c01b3248: 3c 4e cmp $0x4e,%al
c01b324a: 74 54 je c01b32a0
<veth_route_lookup+0xf4>c01b324c: e9 cd 00 00 00 jmp
c01b331e <veth_route_lookup+0x172>
c01b3251: 8d 76 00 lea 0x0(%esi),%esi
{
case 'H':
/* if dest ip is a host entry */
------- end of makelst code ----------------

--
^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^
Amit Kucheria
EECS Grad. Research Assistant
University of Kansas @ Lawrence
(R)+1-(785)-830 8521 ||| (O)+1-(785)-864 7774
____________________________________________________



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