From patchwork Tue May 20 17:15:18 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pedro Alves X-Patchwork-Id: 1033 Return-Path: X-Original-To: siddhesh@wilcox.dreamhost.com Delivered-To: siddhesh@wilcox.dreamhost.com Received: from homiemail-mx20.g.dreamhost.com (mx2.sub5.homie.mail.dreamhost.com [208.113.200.128]) by wilcox.dreamhost.com (Postfix) with ESMTP id B416336007B for ; Tue, 20 May 2014 10:15:34 -0700 (PDT) Received: by homiemail-mx20.g.dreamhost.com (Postfix, from userid 14314964) id 6933841C93A98; Tue, 20 May 2014 10:15:34 -0700 (PDT) X-Original-To: gdb@patchwork.siddhesh.in Delivered-To: x14314964@homiemail-mx20.g.dreamhost.com Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by homiemail-mx20.g.dreamhost.com (Postfix) with ESMTPS id 48A5C41C93AAF for ; Tue, 20 May 2014 10:15:34 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:message-id:date:from:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; q=dns; s=default; b=SOfbnzdFxmTdJ8Rp DbrfMF1JcCJWIKMdp1tCr7/m0+f4TvIy2Fa07YxhhfwJNQ6kf1UoCcA271UHDKmS 5onSA5GEqUgb0gbq/XPx5bcfwyAi9S7/J40TqH2JhCWfviEqyn3HPcD/5Bf3nc0w fM1X+p3u1sIvEI88KN7QpmU3o/0= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:message-id:date:from:mime-version:to:cc :subject:references:in-reply-to:content-type :content-transfer-encoding; s=default; bh=Ox752MjUx4S3H6L0qFD8xd aocQE=; b=xoeaPbjpY1x66u1fFHjpplWMKfYQ2ZIP0aDdZ6Vja0E/Luyr2bJbvm UTE2RssUJYcnhhr0YlJG9qK1d+hWBNBHMEoNP4kPAc3sT2PgxnvQL7i7yoXmkPfF gojVSOKT2xp5VqttkRw4F+EXy6pJjo1zX5/9M+5GNNqOOKeQmlICk= Received: (qmail 26643 invoked by alias); 20 May 2014 17:15:32 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 26627 invoked by uid 89); 20 May 2014 17:15:31 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.2 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; Tue, 20 May 2014 17:15:26 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s4KHFK1i002719 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 20 May 2014 13:15:21 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s4KHFIgH015672; Tue, 20 May 2014 13:15:19 -0400 Message-ID: <537B8DA6.4080601@redhat.com> Date: Tue, 20 May 2014 18:15:18 +0100 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: "Metzger, Markus T" CC: "gdb-patches@sourceware.org" Subject: [PATCH] Make the dcache (code/stack cache) handle line reading errors better. References: <1396601586-24380-1-git-send-email-markus.t.metzger@intel.com> <53760BDF.2080500@redhat.com> <537A7A80.3050801@redhat.com> <537B389C.4080901@redhat.com> In-Reply-To: X-DH-Original-To: gdb@patchwork.siddhesh.in On 05/20/2014 12:14 PM, Metzger, Markus T wrote: >> From: Pedro Alves [mailto:palves@redhat.com] >> On 05/20/2014 07:40 AM, Metzger, Markus T wrote: >> >>>> Does this patch fix it ? >>> >>> It does when we request TARGET_OBJECT_MEMORY. >> >> You mean, the patch should have been: >> >> - return ops->to_xfer_partial (ops, TARGET_OBJECT_RAW_MEMORY, >> + return ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, >> >> ? > > Yes. Oh, indeed. The targets should never see requests for any other kind of memory but TARGET_OBJECT_MEMORY. I even recall now pushing btrace in that direction. :-) Here's a full patch. I managed to come up with a test that doesn't depend on btrace. Let me know what you think. 8<--------------- From: Pedro Alves Date: Tue, 20 May 2014 12:26:01 +0100 Subject: [PATCH] Make the dcache (code/stack cache) handle line reading errors better. The dcache (code/stack cache) is supposed to be transparent, but it's actually not in one case. dcache tries to read chunks (cache lines) at a time off of the target. This may end up trying to read unaccessible or unavailable memory. Currently the caller an xfer error in this case. But if the specific bits of memory the caller actually wanted are available and accessible, then the caller should get the memory it wanted, not an error. gdb/ 2014-05-20 Pedro Alves * dcache.c (dcache_read_memory_partial): If reading the cache line fails, fallback to reading just the memory the caller wanted. gdb/testsuite/ 2014-05-20 Pedro Alves * gdb.base/dcache-line-read-error.c * gdb.base/dcache-line-read-error.exp --- gdb/dcache.c | 7 +- gdb/testsuite/gdb.base/dcache-line-read-error.c | 108 ++++++++++++++++++++++ gdb/testsuite/gdb.base/dcache-line-read-error.exp | 84 +++++++++++++++++ 3 files changed, 197 insertions(+), 2 deletions(-) create mode 100644 gdb/testsuite/gdb.base/dcache-line-read-error.c create mode 100644 gdb/testsuite/gdb.base/dcache-line-read-error.exp diff --git a/gdb/dcache.c b/gdb/dcache.c index d3b546b..9780f4d 100644 --- a/gdb/dcache.c +++ b/gdb/dcache.c @@ -497,8 +497,11 @@ dcache_read_memory_partial (struct target_ops *ops, DCACHE *dcache, if (i == 0) { - /* FIXME: We lose the real error status. */ - return TARGET_XFER_E_IO; + /* Even though reading the whole line failed, we may be able to + read a piece starting where the caller wanted. */ + return ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL, + myaddr, NULL, memaddr, len, + xfered_len); } else { diff --git a/gdb/testsuite/gdb.base/dcache-line-read-error.c b/gdb/testsuite/gdb.base/dcache-line-read-error.c new file mode 100644 index 0000000..86e512d --- /dev/null +++ b/gdb/testsuite/gdb.base/dcache-line-read-error.c @@ -0,0 +1,108 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2012-2014 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include +#include +#include +#include +#include + +size_t pg_size; +void *first_mapped_page; +void *first_unmapped_page; +void *last_mapped_page; +void *last_unmapped_page; + +void +breakpt (void) +{ + /* Nothing. */ +} + +int +main (void) +{ + void *p; + int pg_count; + size_t i; + + /* Map 6 contiguous pages, and then unmap all second first, and + second last. + + From GDB we will disassemble each of the _mapped_ pages, with a + code-cache (dcache) line size bigger than the page size (twice + bigger). This makes GDB try to read one page before the mapped + page once, and the page after another time. GDB should give no + error in either case. + + That is, depending on what the kernel gives up, we get either: + + .---.---.---.---.---.---. + | U | M | U | U | M | U | + '---'---'---'---'---'---. + | | | | <- line alignment + ^^^^^^^ ^^^^^^^ + | | + + line1 + line2 + + Or: + + .---.---.---.---.---.---. + | U | M | U | U | M | U | + '---'---'---'---'---'---. + | | | <- line alignment + ^^^^^^^ ^^^^^^^ + | | + line1 + + line2 + + Note we really want to test that dcache behaves correctly when + reading a cache line fails. We're just using unmapped memory as + proxy for any kind of error. */ + + pg_size = getpagesize (); + pg_count = 6; + + p = mmap (0, pg_count * pg_size, PROT_READ|PROT_WRITE, + MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); + if (p == MAP_FAILED) + { + perror ("mmap"); + return EXIT_FAILURE; + } + + /* Disassembling 0s should behave on all targets. */ + memset (p, 0, pg_count * pg_size); + + for (i = 0; i < pg_count; i++) + { + if (i == 1 || i == 4) + continue; + + if (munmap (p + (i * pg_size), pg_size) == -1) + { + perror ("munmap"); + return EXIT_FAILURE; + } + } + + first_mapped_page = p + 1 * pg_size;; + last_mapped_page = p + 4 * pg_size; + + breakpt (); + + return EXIT_SUCCESS; +} diff --git a/gdb/testsuite/gdb.base/dcache-line-read-error.exp b/gdb/testsuite/gdb.base/dcache-line-read-error.exp new file mode 100644 index 0000000..c3b2f9f --- /dev/null +++ b/gdb/testsuite/gdb.base/dcache-line-read-error.exp @@ -0,0 +1,84 @@ +# Copyright 2014 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +# Test that dcache behaves correctly when reading a cache line fails. + +standard_testfile + +if { [prepare_for_testing "failed to prepare" ${testfile}] } { + return -1 +} + +if ![runto breakpt] { + return -1 +} + +# Disassemble WHAT. + +proc disassemble { what } { + global hex gdb_prompt + + set cmd "disassemble $what" + gdb_test_multiple $cmd $cmd { + -re "Cannot access memory.*$gdb_prompt $" { + fail $cmd + } + -re "End of assembler dump\.\r\n$gdb_prompt $" { + pass $cmd + } + } +} + +# Issue the "delete mem" command. This makes GDB ignore the +# target-provided list, if any. + +proc delete_mem {} { + global gdb_prompt + + set test "delete mem" + gdb_test_multiple $test $test { + -re "Delete all memory regions.*y or n.*$" { + send_gdb "y\n" + exp_continue + } + -re "$gdb_prompt $" { + pass $test + } + } +} + +# Make the dcache line size bigger than the pagesize. +set pagesize [get_integer_valueof "pg_size" -1] +set linesize [expr $pagesize * 2] + +gdb_test_no_output "set dcache line-size $linesize" \ + "set dcache line size to twice the pagesize" + +gdb_test "info dcache" \ + "Dcache 4096 lines of $linesize bytes each.\r\nNo data cache available." + +# Make sure dcache doesn't automatically skip unmapped regions. +delete_mem + +gdb_test "info mem" \ + "Using user-defined memory regions.\r\nThere are no memory regions defined\." + +# Given the line size is bigger than the page size, we have +# alternating mapped and unmapped pages, these make dcache fail to +# fill in the cache line. GDB used to have a bug where that failure +# would end up as user-visible error. The range being disassembled is +# wholly available, so GDB should succeed. +disassemble "first_mapped_page, +10" +disassemble "last_mapped_page, +10"