On Sat, Oct 10, 2009 at 2:05 PM, Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> wrote: > > Holger Kiehl wrote: > >> How can I find which register is fsa_pos? > > fsa_pos is a parameter, and doesn't appear to be changed within the > function, so I would expect "print fsa_pos" to give the correct value. > > AFAICT, the following portion of the disassembly: > > 0x0000000000404b49 <start_process+121>: movslq 0x24(%rsp),%rax > 0x0000000000404b4e <start_process+126>: imul $0x8f8,%rax,%r14 > 0x0000000000404b55 <start_process+133>: mov %r14,%rax > 0x0000000000404b58 <start_process+136>: add 0x225441(%rip),%rax # 0x629fa0 <fsa> > 0x0000000000404b5f <start_process+143>: mov 0xec(%rax),%edx > 0x0000000000404b65 <start_process+149>: test $0x1,%dl > > corresponds to the expression > > fsa[fsa_pos].host_status & DO_NOT_DELETE_DATA > > 0x24(%rsp) is fsa_pos, $0x8f8 (2296) is the size of each element of > fsa[], 0x225441(%rip) is fsa, 0xec is the offset of the host_status > field. > > So: > > movslq 0x24(%rsp),%rax # %rax = fsa_pos > imul $0x8f8,%rax,%r14 # %r14 = fsa_pos * sizeof(fsa[i]) = &fsa[fsa_pos] - &fsa[0] > mov %r14,%rax # %rax = &fsa[fsa_pos] - &fsa[0] > add 0x225441(%rip),%rax # %rax = &fsa[fsa_pos] > mov 0xec(%rax),%edx # %edx = fsa[fsa_pos].host_status > > Based upon this, %r14 should contain fsa_pos * 2296, so: > >> (gdb) info registers >> r14 0xfffffffffffff708 -2296 > > Which suggests that fsa_pos is -1. Excellent Glynn .... thanks :-) . I was having trouble deciphering it . > > -- > Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> > -- Thanks - Manish ================================== [$\*.^ -- I miss being one of them ================================== -- To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
