Messages in this thread | | | Date | Tue, 14 Aug 2012 16:27:36 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2 2/5] x86/uprobes: implement x86 specific arch_uprobe_*_step |
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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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