From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 73825 invoked by alias); 24 Jan 2019 17:09:42 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 73718 invoked by uid 89); 24 Jan 2019 17:09:42 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,SPF_PASS autolearn=ham version=3.3.2 spammy=HContent-Transfer-Encoding:8bit X-HELO: mx2.freebsd.org Received: from mx2.freebsd.org (HELO mx2.freebsd.org) (8.8.178.116) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 24 Jan 2019 17:09:40 +0000 Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client CN "mx1.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx2.freebsd.org (Postfix) with ESMTPS id 7B42A98E1E for ; Thu, 24 Jan 2019 17:09:38 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id BC47C735F1 for ; Thu, 24 Jan 2019 17:09:37 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from John-Baldwins-MacBook-Pro-3.local (ralph.baldwin.cx [66.234.199.215]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: jhb) by smtp.freebsd.org (Postfix) with ESMTPSA id 69F151F185 for ; Thu, 24 Jan 2019 17:09:37 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Subject: Re: [PATCH 5/9] Add a helper function to resolve TLS variable addresses for FreeBSD. From: John Baldwin To: gdb-patches@sourceware.org References: Openpgp: preference=signencrypt Message-ID: Date: Thu, 24 Jan 2019 17:09:00 -0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: BC47C735F1 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.97 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.999,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; NEURAL_HAM_SHORT(-0.97)[-0.975,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-IsSubscribed: yes X-SW-Source: 2019-01/txt/msg00540.txt.bz2 On 1/22/19 10:42 AM, John Baldwin wrote: > The fbsd_get_thread_local_address function accepts the base address of > a thread's DTV array and the base address of an object file's link map > and uses this to compute a TLS variable's address. FreeBSD > architectures use an architecture-specific method to determine the > address of the DTV array pointer and call this helper function to > perform the rest of the address calculation. > > * fbsd-tdep.c (fbsd_pspace_data_handle): New variable. > (struct fbsd_pspace_data): New type. > (get_fbsd_pspace_data, fbsd_pspace_data_cleanup) > (fbsd_read_integer_by_name, fbsd_fetch_rtld_offsets) > (fbsd_get_tls_index, fbsd_get_thread_local_address): New function. > (_initialize_fbsd_tdep): Initialize 'fbsd_pspace_data_handle'. > * fbsd-tdep.c (fbsd_get_thread_local_address): New prototype. > --- > gdb/ChangeLog | 10 ++++ > gdb/fbsd-tdep.c | 146 ++++++++++++++++++++++++++++++++++++++++++++++++ > gdb/fbsd-tdep.h | 10 ++++ > 3 files changed, 166 insertions(+) > > diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c > index d971d3a653..2e0f72d17b 100644 > --- a/gdb/fbsd-tdep.c > +++ b/gdb/fbsd-tdep.c > + > +/* Lookup offsets of fields in the runtime linker's 'Obj_Entry' > + structure needed to determine the TLS index of an object file. */ > + > +static void > +fbsd_fetch_rtld_offsets (struct gdbarch *gdbarch, struct fbsd_pspace_data *data) > +{ > + TRY > + { > + /* Fetch offsets from debug symbols in rtld. */ > + data->off_linkmap = parse_and_eval_long ("&((Obj_Entry *)0)->linkmap"); > + data->off_tlsindex = parse_and_eval_long ("&((Obj_Entry *)0)->tlsindex"); > + data->rtld_offsets_valid = true; > + return; I'm not really happy about using parse_and_eval_long with an open-coded equivalent of offsetof() here. It seems we don't already have existing functionality for this though? I think I could use 'lookup_struct' to find the 'struct type *' for 'Obj_Entry', but if I used 'lookup_struct_elt_type' to get the type of an element that doesn't give me anything that has the offset. We could perhaps instead add a new function 'lookup_struct_elt_offset' that took the element name as a string and figured out the offset. We could then use this to provide an 'offsetof' builtin for the C language perhaps. However, I suspect that lookup_struct_elt_offset would have to invoke a language-specific function to do the actual computation (just as ptype /o handling is language-specific). -- John Baldwin                                                                            Â