Hi,
I am using sles10sp2 beta kernel(x86_64) in which the new backtrace
mechanism for x86 is used.
I was attemptting to use bb1 command to analysis
do_hypervisor_callback and evtchn_do_upcall. In SLES10Sp2,
do_hypervisor_callback is defined in arch/x86_64/kernel/entry-xen.S,
although there is no such a file in the mainline kernel, but I think
this has nothing to do with the problem.
below is the disassemble result of
do_hypervisor_callback.(evtchn_do_upcall is called by
do_hypervisor_callback).
[0]kdb> id do_hypervisor_callback
0xffffffff8010ab7c do_hypervisor_callback: mov %rdi,%rsp
0xffffffff8010ab7f do_hypervisor_callback+0x3: incl %gs:0x20
0xffffffff8010ab87 do_hypervisor_callback+0xb: mov %rsp,%rbp
0xffffffff8010ab8a do_hypervisor_callback+0xe: cmove %gs:0x28,%rsp
0xffffffff8010ab94 do_hypervisor_callback+0x18: push %rbp
0xffffffff8010ab95 do_hypervisor_callback+0x19: callq
0xffffffff80281871 evtchn_do_upcall
0xffffffff8010ab9a do_hypervisor_callback+0x1e: pop %rsp
0xffffffff8010ab9b do_hypervisor_callback+0x1f: decl %gs:0x20
0xffffffff8010aba3 do_hypervisor_callback+0x27: jmpq
0xffffffff8010aaef error_exit
0xffffffff8010aba8 restore_all_enable_events: mov %gs:0x24,%rsi
0xffffffff8010abb1 restore_all_enable_events+0x9: shl $0x20,%rsi
0xffffffff8010abb5 restore_all_enable_events+0xd: shr $0x1a,%rsi
0xffffffff8010abb9 restore_all_enable_events+0x11: add
0xffffffff8039d628,%rsi
0xffffffff8010abc1 restore_all_enable_events+0x19: movb $0x0,0x1(%rsi)
Here we see 0xffffffff8010ab9a is the exit point of evtchn_do_upcall.
However bb1 command fails when I tried to give it this address.
[0]kdb> bb1 0xffffffff8010ab9a
bb_pass1: func_name do_hypervisor_callback func_start
0xffffffff8010ab7c func_end 0xffffffff8010aba8
bb_pass1: end
bb[0] start 0xffffffff8010ab7c end 0xffffffff8010aba3 drop_through 0
bb_pass2: start
bb_pass2_do_changed_blocks: allow_missing 0
bb[0]
bb_reg_state ffffffff805153d8
rax = rax
rbx = rbx
rcx = rcx
rdx = rdx
rdi = rdi
rsi = rsi
rbp = rbp
rsp = osp+0x0
r8 = r8
r9 = r9
r10 = r10
r11 = r11
r12 = r12
r13 = r13
r14 = r14
r15 = r15
'0xffffffff8010ab7c do_hypervisor_callback: mov %rdi,%rsp'
opcode 'mov' matched by 'mov', usage 36
src R: %rdi base_rc 6 (rdi)
dst R: %rsp base_rc 9 (rsp)
rsp = rdi (rdi)
'0xffffffff8010ab7f do_hypervisor_callback+0x3: incl %gs:0x20'
opcode 'incl' matched by 'inc', usage 5
src M: %gs:0x20
'0xffffffff8010ab87 do_hypervisor_callback+0xb: mov %rsp,%rbp'
opcode 'mov' matched by 'mov', usage 36
src R: %rsp base_rc 9 (rsp)
dst R: %rbp base_rc 8 (rbp)
rbp = rsp (rdi)
'0xffffffff8010ab8a do_hypervisor_callback+0xe: cmove %gs:0x28,%rsp'
opcode 'cmove' matched by 'cmov', usage 19
src M: %gs:0x28
dst R: %rsp base_rc 9 (rsp)
'0xffffffff8010ab94 do_hypervisor_callback+0x18: push %rbp'
opcode 'push' matched by 'push', usage 44
src R: %rbp base_rc 8 (rbp)
push when BBRG_RSP is undefined?
bb_pass2: end bb_reg_params 0 bb_memory_params 0
kdb_bb: 0xffffffff8010ab9a [kernel]do_hypervisor_callback failed at
0xffffffff8010ab94
It's very clear why this issue happens, since the first step of this
function, rsp becomes no longer being referenced by osp. My question
is, is there any way to fix this?
Regards
Jason
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