bochs/gdb weirdness with register values
Posted: Sun Jan 27, 2013 11:53 am
I am using gdb with bochs and it is mixing up the values of the different registers. Below is the output from gdb followed by the output from bochs when I terminate bochs at the breakpoint. It seems that bochs is getting the registers correct while gdb is mixing them up. gdb is getting the right numbers but calling them by the wrong register name. For example, gdb reports eip as "4" while it is actually esi which has the value "4". Does anybody know why this is happening? Thank you.
Code: Select all
(gdb) b SyscallHandler
Breakpoint 1 at 0x1a3a4: file kernel/syscall.c, line 43.
(gdb) c
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
0x00000004 in ?? ()
(gdb) info registers
eax 0xffbf7fbf -4227137
ecx 0x0 0
edx 0x1 1
ebx 0x0 0
esp 0x4025a4 0x4025a4
ebp 0x0 0x0
esi 0xffbf7fbf -4227137
edi 0x0 0
eip 0x4 0x4
eflags 0x0 [ ]
cs 0x0 0
ss 0x0 0
ds 0xffbf7fb3 -4227149
es 0x0 0
fs 0xffbf7f47 -4227257
gs 0x0 0
Code: Select all
00021550785i[CPU0 ] | RAX=00000000ffbf7fbf RBX=0000000000000001
00021550785i[CPU0 ] | RCX=00000000004025a4 RDX=00000000ffbf7fbf
00021550785i[CPU0 ] | RSP=00000000ffbf7f47 RBP=00000000ffbf7fb3
00021550785i[CPU0 ] | RSI=0000000000000004 RDI=0000000000000000
00021550785i[CPU0 ] | R8=0000000000000000 R9=0000000000000000
00021550785i[CPU0 ] | R10=0000000000000000 R11=0000000000000000
00021550785i[CPU0 ] | R12=0000000000000000 R13=0000000000000000
00021550785i[CPU0 ] | R14=0000000000000000 R15=0000000000000000
00021550785i[CPU0 ] | IOPL=0 id vip vif ac vm rf nt of df if tf sf ZF af PF cf
00021550785i[CPU0 ] | SEG selector base limit G D
00021550785i[CPU0 ] | SEG sltr(index|ti|rpl) base limit G D
00021550785i[CPU0 ] | CS:0008( 0001| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | DS:0010( 0002| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | SS:0010( 0002| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | ES:0010( 0002| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | FS:0010( 0002| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | GS:0010( 0002| 0| 0) 00000000 ffffffff 1 1
00021550785i[CPU0 ] | MSR_FS_BASE:0000000000000000
00021550785i[CPU0 ] | MSR_GS_BASE:0000000000000000
00021550785i[CPU0 ] | RIP=000000000001a3a4 (000000000001a3a4)