From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Wed, 28 Sep 2016 18:12:10 +0100 Subject: [PATCH 5/5] arm64: Add uprobe support In-Reply-To: References: <20160921170403.GE12180@e104818-lin.cambridge.arm.com> <20160922032328.GB29470@localhost.localdomain> <20160922165030.GA27704@e104818-lin.cambridge.arm.com> <20160923041230.GC29470@localhost.localdomain> <20160923130528.GE2161@e104818-lin.cambridge.arm.com> <20160926110159.GB27498@e104818-lin.cambridge.arm.com> <20160926130359.GA9370@localhost.localdomain> <20160927135133.GF17336@e104818-lin.cambridge.arm.com> Message-ID: <20160928171210.GC29934@e104818-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. -- Catalin