Date: Tue, 8 Nov 2011 20:09:49 -0500 From: Arnaud Lacombe <lacombar@gmail.com> To: Andriy Gapon <avg@freebsd.org> Cc: Attilio Rao <attilio@freebsd.org>, freebsd-current@freebsd.org Subject: Re: Using Instruction Pointer address in debug interfaces [Was: Re: vm_page_t related KBI [Was: Re: panic at vm_page_wire with FreeBSD 9.0 Beta 3]] Message-ID: <CACqU3MWKYCX3o3jC7N1tA=0QSP8RNTKT2qZnFGuTNbavDuihYg@mail.gmail.com> In-Reply-To: <4EB9975F.4090601@FreeBSD.org> References: <CACqU3MU_Bk%2BcObCiUa2XtM7fLkSpSDzOZqoZ=khNOR-_6ptYYQ@mail.gmail.com> <CAJ-FndDOWpotphH4pmn0S6QqJybx74A2Kt4a8aiT96x0f2cRZA@mail.gmail.com> <4EB9975F.4090601@FreeBSD.org>
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Hi, On Tue, Nov 8, 2011 at 3:55 PM, Andriy Gapon <avg@freebsd.org> wrote: > > [cc list trimmed] > > on 08/11/2011 22:34 Attilio Rao said the following: >> 2011/11/8 Arnaud Lacombe <lacombar@gmail.com>: >>> To avoid future complaints about the fact that I would be only "talk" >>> without "action", I did implement what I suggested above. As it is >>> quite a large patch-set, I will not post it directly here, however, it >>> is available on github: >> >> I really think that this is way too dependent by the good health of >> your tool, thus that is highly fragile. >> >> However, you may have more luck by just the core of your kernel >> changes here, for comment and leave alone all the (ptr -> >> LOCK_FILE/LOCK_LINE conversion). >> >> Said that, I think this logic is too fragile and likely won't be as >> effective as __FILE__/__LINE__ in many cases. > > I agree. > If we were able to somehow automatically, magically, easily and correctly > determine an instruction pointer of a caller, then it would make sense to ditch > explicit passing of __FILE__/__LINE__ arguments in favor of doing instruction > pointer decoding. > again, no need for magic, this already exists, as the form of gcc[0]'s __builtin_return_address(0). > But if we are just replacing explicit passing of (well-known) macros > __FILE__/__LINE__ with explicit passing of THIS_IP, then I don't see a point. > make sense too, but you need to be sure stuff between the caller and callee is fully inlined. > Apologies if I missed the rationale for this change. > mostly getting rid of all the __FILE__ and __LINE__ bloat. - Arnaud [0]: check about LLVM support is left to the reader.
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