Re: [PATCH 5/5] arm64: Add uprobe support

From: Catalin Marinas
Date: Wed Sep 28 2016 - 13:12:28 EST

On Tue, Sep 27, 2016 at 08:33:25PM +0530, Pratyush Anand wrote:
> On Tuesday 27 September 2016 07:21 PM, Catalin Marinas wrote:
> >There is also the is_trap_at_addr() function which uses is_trap_insn().
> >I haven't checked the call paths here, are there any implications if
> >is_trap_insn() always returns false?
> I had looked into it and also tested that a tracepoint at an application
> having a same instruction as that of "uprobe break instruction" ie "BRK
> #0x5" is rejected. So, I think a false positive return from is_tarp_insn()
> is still OK.

Looking at handle_swbp(), if we hit a breakpoint for which we don't have
a valid uprobe, this function currently sends a SIGTRAP. But if
is_trap_insn() returns false always, is_trap_at_addr() would return 0 in
this case so the SIGTRAP is never issued.