Date: Mon, 1 Dec 2014 16:13:43 -0800 From: Mark Johnston <markj@freebsd.org> To: Fedor Indutny <fedor@indutny.com> Cc: "freebsd-dtrace@freebsd.org" <freebsd-dtrace@freebsd.org> Subject: Re: DTrace fixes for node.js Message-ID: <20141202001342.GH48232@charmander.picturesperfect.net> In-Reply-To: <CAEv2Vf%2BbthtCD6OeQbhWf81_ArM6x0PDXn8GO0nLFBs8n5CKNA@mail.gmail.com> References: <CAEv2VfLJR7b9Gj7qN9VuuQKWphUUrdJYwQ4r5P%2BKWJYLuddCiA@mail.gmail.com> <20140227050136.GB28089@raichu> <CAEv2Vf%2BHh-K11ika7-awEwFE67OM=Du8Pn9sWvC1cwuVBmSjxw@mail.gmail.com> <CAMw1wOwwk8tZxFmxTpV04y04-Dqj9vdDwwprrv2BeQcCtV0z6g@mail.gmail.com> <CAEv2VfL9h4FUaFgDGCMDuQ_1d3tK3K_e19bBw3kvD0hun4P=Kg@mail.gmail.com> <CAEv2VfLXmnfAHdXDF9CExVPjX_BVRGQiYhQQ29nnDFnGNhaa-Q@mail.gmail.com> <20141201215430.GD48232@charmander.picturesperfect.net> <CAEv2Vf%2BbthtCD6OeQbhWf81_ArM6x0PDXn8GO0nLFBs8n5CKNA@mail.gmail.com>
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On Tue, Dec 02, 2014 at 03:02:19AM +0400, Fedor Indutny wrote: > Mark, > > Yes, 271413 is the one fixing PROGBITS. Anyway, my patch should > support both PROGBITS and DOFW_sun, making it quite universal. But why is it necessary? As of r271413, the DOF section type should always be SUNW_dof. If not, that's unexpected, and I'd like to understand what's going on. On 10.1, we're still creating a section of type PROGBITS, and that's what drti.o is looking for. Is there a regression? Thanks, -Mark > > Thank you for your time! > > Fedor. > > On Tue, Dec 2, 2014 at 12:54 AM, Mark Johnston <markj@freebsd.org> wrote: > > > On Mon, Dec 01, 2014 at 04:59:02PM +0400, Fedor Indutny wrote: > > > Hello Mark, DTrace people! > > > > > > > Hi Fedor, > > > > > Hope you are doing well. > > > > > > Looks like FreeBSD 10.1 decided to play some not that funny games > > > with drti.c again :) > > > > > > I have submitted a [patch][0] as a problem report. > > > > Thank you. I'll test and commit it if I don't run into any problems. > > > > > > > > It fixes iteration over aligned DOFs, and accounts for a > > > non-master-branch FreeBSD stuff in: > > > > > > cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c > > > > > > Which is currently producing SHT_PROGBITS section instead of > > > expected SHT_SUNW_dof, thus confusing the drti.c file. > > > > Hm, are you referring to this change: > > https://svnweb.freebsd.org/base?view=revision&revision=271413 > > ? > > > > I'm a bit confused, as it hasn't been merged to 10 yet: it exposed > > another dtrace bug that caused build failures in some USDT-enabled > > ports, so I'm waiting for the subsequent fixes to settle. > > > > -Mark > > > > > > > > Thank you, > > > Fedor. > > > > > > [0]: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195555 > > > > > > > > > On Thu, Feb 27, 2014 at 6:50 PM, Fedor Indutny <fedor@indutny.com> > > wrote: > > > > > > > Update sent, thank you! > > > > > > > > On Thu, Feb 27, 2014 at 6:39 PM, Mark Johnston <markj@freebsd.org> > > wrote: > > > > > On Thu, Feb 27, 2014 at 3:30 AM, Fedor Indutny <fedor@indutny.com> > > > > wrote: > > > > >> Mark, > > > > >> > > > > >> Thanks for looking into this. I just tried your patch and it (no > > > > >> surprise) builds fine. Node.js DOF symbols seems to be resolving > > > > >> properly too! > > > > >> > > > > >> Do you want me to squash this changes into my patch, and post them > > on > > > > >> that ticket? > > > > >> > > > > > > > > > > That would be good, thanks. When I have some time I'll do more > > testing > > > > > and commit the change. > > > > > > > > > > -Mark > > > > > > > > > >> On Thu, Feb 27, 2014 at 9:01 AM, Mark Johnston <markj@freebsd.org> > > > > wrote: > > > > >>> On Tue, Feb 25, 2014 at 06:16:15PM +0400, Fedor Indutny wrote: > > > > >>>> Hello devs! > > > > >>>> > > > > >>>> I have made some fixes to fix DTrace support for node.js in > > FreeBSD: > > > > >>>> > > > > >>>> * http://www.freebsd.org/cgi/query-pr.cgi?pr=186821 > > > > >>>> * http://www.freebsd.org/cgi/query-pr.cgi?pr=187027 > > > > >>>> > > > > >>>> Here is a blog post with a bit of explanation of why this is > > needed > > > > >>>> and what is fixed: https://blog.indutny.com/7.freebsd-dtrace > > > > >>>> > > > > >>>> Please let me know if I could be any help in reviewing it. > > > > >>> > > > > >>> Hi Fedor, > > > > >>> > > > > >>> The DOF limit change looks fine to me. I note that the illumos guys > > > > have > > > > >>> just pushed a change to illumos-gate which bumps > > dtrace_dof_maxsize, > > > > but > > > > >>> it's good to have the sysctl as well. > > > > >>> > > > > >>> The drti change looks mostly good to me. The real problem there is > > that > > > > >>> our linker doesn't know how to merge DOF, so it just concatenates > > the > > > > >>> tables into one SUNW_dof section. So we should really fix our > > linker, > > > > >>> but it doesn't hurt to also handle the problem in drti.o. > > > > >>> > > > > >>> There are a couple of bugs in the patch. First, the "break" added > > after > > > > >>> finding the DOF section causes problems if we haven't yet seen the > > > > >>> symbol table. Second, fixedprobes needs to be reset at the > > beginning of > > > > >>> each iteration of the while loop that you added, else we may not > > try > > > > >>> searching the dynamic symbol table when fixing the probe addresses. > > > > I've > > > > >>> pasted a patch below; could you test it and make sure things still > > work > > > > >>> properly with node? > > > > >>> > > > > >>> Thanks for the detailed blog post and problem description, they > > were > > > > >>> very helpful. :) > > > > >>> > > > > >>> -Mark > > > > >>> > > > > >>> diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/drti.c > > > > b/cddl/contrib/opensolaris/lib/libdtrace/common/drti.c > > > > >>> index e47cfb4d..bb02d8c 100644 > > > > >>> --- a/cddl/contrib/opensolaris/lib/libdtrace/common/drti.c > > > > >>> +++ b/cddl/contrib/opensolaris/lib/libdtrace/common/drti.c > > > > >>> @@ -162,7 +162,7 @@ dtrace_dof_init(void) > > > > >>> char *dofstrtabraw; > > > > >>> size_t shstridx, symtabidx = 0, dynsymidx = 0; > > > > >>> unsigned char *buf; > > > > >>> - int fixedprobes = 0; > > > > >>> + int fixedprobes; > > > > >>> #endif > > > > >>> > > > > >>> if (getenv("DTRACE_DOF_INIT_DISABLE") != NULL) > > > > >>> @@ -214,7 +214,6 @@ dtrace_dof_init(void) > > > > >>> if (s && strcmp(s, ".SUNW_dof") == 0) { > > > > >>> dofdata = elf_getdata(scn, NULL); > > > > >>> dof = dofdata->d_buf; > > > > >>> - break; > > > > >>> } > > > > >>> } > > > > >>> } > > > > >>> @@ -226,6 +225,7 @@ dtrace_dof_init(void) > > > > >>> } > > > > >>> > > > > >>> while ((char *) dof < (char *) dofdata->d_buf + > > > > dofdata->d_size) { > > > > >>> + fixedprobes = 0; > > > > >>> dof_next = (void *) ((char *) dof + > > dof->dofh_filesz); > > > > >>> #endif > > > > >>> > > > > > >
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