On 08/14, Sebastian Andrzej Siewior wrote:
>
> On 08/13/2012 03:24 PM, Oleg Nesterov wrote:
>>
>> this patch still adds restore_flags into arch_uprobe_task.
>
> Yes, but
OOPS. Yes, we need a new member in ->utask now to record the state
of TIF_SINGLESTEP (X86_EFLAGS_TF actually).
I meant that, since the patch still uses TIF_SINGLESTEP,
arch_uprobe_disable_step() can check it but somehow I forgot that
since arch_uprobe_enable_step() still does user_enable_single_step()
TIF_SINGLESTEP is always set.
>>> static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
>>> {
>>> - bool fix_ip = true, fix_call = false; /* defaults */
>>> + bool fix_ip = true, fix_call = false, fix_tf = false; /* defaults */
>>> int reg;
>>>
>>> insn_get_opcode(insn); /* should be a nop */
>>>
>>> switch (OPCODE1(insn)) {
>>> + case 0x9d:
>>> + /* popf */
>>> + fix_tf = true;
>>> + break;
>>> case 0xc3: /* ret/lret */
>>> case 0xcb:
>>> case 0xc2:
>>> @@ -277,6 +284,8 @@ static void prepare_fixups(struct arch_uprobe *auprobe,
>>> struct insn *insn)
>>> auprobe->fixups |= UPROBE_FIX_IP;
>>> if (fix_call)
>>> auprobe->fixups |= UPROBE_FIX_CALL;
>>> + if (fix_tf)
>>> + auprobe->fixups |= UPROBE_TF_CHANGES;
>>> }
>>
>> I won't insist, but do we really need fix_tf? "case 0x9d" could simply
>> add UPROBE_TF_CHANGES.
>
> if it is not 0x9d (in most cases) we need to decide on per-process
> basis (not per-breakpoint) whether the task has gdb watching it or not.
Yes, yes, I see, thanks.
But this doesn't explain why do we need to add the new variable, fix_tf.
case 0x9d:
auprobe->fixups |= UPROBE_TF_CHANGES;
break;
seems enough.
Oleg.
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