From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18722 invoked by alias); 6 Oct 2013 19:51:19 -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 18710 invoked by uid 89); 6 Oct 2013 19:51:19 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-4.2 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 06 Oct 2013 19:51:18 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r96JpGO6017719 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Sun, 6 Oct 2013 15:51:16 -0400 Received: from host2.jankratochvil.net (ovpn-116-31.ams2.redhat.com [10.36.116.31]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r96JpC3j032200 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Sun, 6 Oct 2013 15:51:15 -0400 Date: Sun, 06 Oct 2013 19:51:00 -0000 From: Jan Kratochvil To: Markus Metzger Cc: gdb-patches@sourceware.org, Pedro Alves Subject: Re: [patch v6 19/21] btrace, gdbserver: read branch trace incrementally Message-ID: <20131006195112.GE28020@host2.jankratochvil.net> References: <1379676639-31802-1-git-send-email-markus.t.metzger@intel.com> <1379676639-31802-20-git-send-email-markus.t.metzger@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1379676639-31802-20-git-send-email-markus.t.metzger@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-IsSubscribed: yes X-SW-Source: 2013-10/txt/msg00169.txt.bz2 On Fri, 20 Sep 2013 13:30:37 +0200, Markus Metzger wrote: > --- a/gdb/btrace.c > +++ b/gdb/btrace.c [...] > @@ -717,27 +717,149 @@ btrace_teardown (struct thread_info *tp) > btrace_clear (tp); > } > > +/* Adjust the block trace in order to stitch old and new trace together. > + Return 0 on success, -1 otherwise. */ Document parameters (what is input, what is output). > + > +static int > +btrace_stitch_trace (VEC (btrace_block_s) **btrace, > + const struct btrace_thread_info *btinfo) > +{ > + struct btrace_function *end; > + struct btrace_insn *insn; > + btrace_block_s *block; > + > + /* If we don't have trace, there's nothing to do. */ > + if (VEC_empty (btrace_block_s, *btrace)) > + return 0; > + > + end = btinfo->end; > + gdb_assert (end != NULL); > + > + block = VEC_last (btrace_block_s, *btrace); > + insn = VEC_last (btrace_insn_s, end->insn); At least call block and insn somehow specific from where they come from. Maybe btrace_block and btinfo_end. Also end should be called btinfo_end (if the extra variable still makes sense in such case). I would even call it new_btrace and old_btinfo with variables old_end etc. > + > + /* If the current PC at the end of the block is the same as in our current > + trace, there are two explanations: > + 1. we executed the instruction and some branch brought us back. > + 2. we have not made any progress. > + In the first case, the delta trace vector should contain at least two > + entries. > + In the second case, the delta trace vector should contain exactly one > + entry for the partial block containing the current PC. Remove it. */ > + if (block->end == insn->pc && VEC_length (btrace_block_s, *btrace) == 1) > + { > + VEC_pop (btrace_block_s, *btrace); > + return 0; > + } > + > + DEBUG ("stitching %s to %s", ftrace_print_insn_addr (insn), > + core_addr_to_string_nz (block->end)); > + > + /* Do a simple sanity check to make sure we don't accidentally end up > + with a bad block. This should not occur in practice. */ > + if (block->end < insn->pc) > + { > + warning (_("Error while trying to read delta trace. Falling back to " > + "a full read.")); > + return -1; > + } > + > + /* We adjust the last block to start at the end of our current trace. */ > + gdb_assert (block->begin == 0); > + block->begin = insn->pc; > + > + /* We simply pop the last insn so we can insert it again as part of > + the normal branch trace computation. > + Since instruction iterators are based on indices in the instructions > + vector, we don't leave any pointers dangling. */ > + DEBUG ("pruning insn at %s for stitching", ftrace_print_insn_addr (insn)); > + > + VEC_pop (btrace_insn_s, end->insn); > + > + /* The instructions vector may become empty temporarily if this has > + been the only instruction in this function segment. > + This violates the invariant but will be remedied shortly. */ > + return 0; > +} [...] > --- a/gdb/common/linux-btrace.h > +++ b/gdb/common/linux-btrace.h > @@ -70,8 +70,12 @@ extern struct btrace_target_info *linux_enable_btrace (ptid_t ptid); > /* Disable branch tracing and deallocate @tinfo. */ > extern int linux_disable_btrace (struct btrace_target_info *tinfo); > > -/* Read branch trace data. */ > -extern VEC (btrace_block_s) *linux_read_btrace (struct btrace_target_info *, > - enum btrace_read_type); > +/* Read branch trace data for the thread indicated by BTINFO into BTRACE > + using the TYPE read method. > + The branch trace will start with the most recent block and continue > + towards older blocks. */ It could also state from to_read_btrace these two things: The vector is cleared before any new data is added. Returns 0 on success; a negative error code, otherwise. And in fact the comment can be merged to to_read_btrace and here to have only: /* See to_read_btrace. */ > +extern int linux_read_btrace (VEC (btrace_block_s) **btrace, > + struct btrace_target_info *btinfo, > + enum btrace_read_type type); > > #endif /* LINUX_BTRACE_H */ [...] > --- a/gdb/gdbserver/linux-low.c > +++ b/gdb/gdbserver/linux-low.c > @@ -5722,17 +5722,27 @@ linux_low_enable_btrace (ptid_t ptid) > return tinfo; > } > > -/* Read branch trace data as btrace xml document. */ > +/* The read_btrace target method. */ /* See to_read_btrace target method. */ (so that ctags and other tools work; I made a "typo" in the review) > > -static void > +static int > linux_low_read_btrace (struct btrace_target_info *tinfo, struct buffer *buffer, > int type) > { [...] > --- a/gdb/target.c > +++ b/gdb/target.c > @@ -4199,18 +4199,19 @@ target_teardown_btrace (struct btrace_target_info *btinfo) > > /* See target.h. */ > > -VEC (btrace_block_s) * > -target_read_btrace (struct btrace_target_info *btinfo, > +int > +target_read_btrace (VEC (btrace_block_s) **btrace, > + struct btrace_target_info *btinfo, > enum btrace_read_type type) > { > struct target_ops *t; > > for (t = current_target.beneath; t != NULL; t = t->beneath) > if (t->to_read_btrace != NULL) > - return t->to_read_btrace (btinfo, type); > + return t->to_read_btrace (btrace, btinfo, type); > > tcomplain (); > - return NULL; > + return ENOSYS; This should be "return -ENOSYS". > } > > /* See target.h. */ [...] Thanks, Jan