From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by sourceware.org (Postfix) with ESMTPS id 3FB8138582AE for ; Thu, 16 Jun 2022 21:14:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 3FB8138582AE Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 25GIYEah029308; Thu, 16 Jun 2022 21:13:58 GMT Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3gqbn3beur-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jun 2022 21:13:57 +0000 Received: from m0098420.ppops.net (m0098420.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 25GKaPE5024177; Thu, 16 Jun 2022 21:13:57 GMT Received: from ppma01dal.us.ibm.com (83.d6.3fa9.ip4.static.sl-reverse.com [169.63.214.131]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3gqbn3beug-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jun 2022 21:13:57 +0000 Received: from pps.filterd (ppma01dal.us.ibm.com [127.0.0.1]) by ppma01dal.us.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 25GL5BrZ021088; Thu, 16 Jun 2022 21:13:56 GMT Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by ppma01dal.us.ibm.com with ESMTP id 3gmjpad81v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jun 2022 21:13:56 +0000 Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 25GLDsdP34800058 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jun 2022 21:13:54 GMT Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3492B13604F; Thu, 16 Jun 2022 21:13:54 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C8E56136051; Thu, 16 Jun 2022 21:13:53 +0000 (GMT) Received: from li-e362e14c-2378-11b2-a85c-87d605f3c641.ibm.com (unknown [9.211.68.56]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 16 Jun 2022 21:13:53 +0000 (GMT) Message-ID: <42e475713eb09bbb0782d21a276bfada0deee440.camel@us.ibm.com> Subject: [PING] [PATCH, v6] Fix reverse stepping multiple contiguous PC ranges over the line table From: Carl Love To: Luis Machado , gdb-patches@sourceware.org Cc: rogealve@br.ibm.com, will_schmidt@vnet.ibm.com, blarsen@redhat.com, Ulrich.Weigand@de.ibm.com Date: Thu, 16 Jun 2022 14:13:53 -0700 In-Reply-To: <20220609130421.245260-1-luis.machado@arm.com> References: <20220609130421.245260-1-luis.machado@arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: wDER838euRifZ-PtX80aDKYzIHJzf116 X-Proofpoint-ORIG-GUID: 0ZqEYh7NbHj1-dZvpXNR5GXjTYz7vvsU Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 2 URL's were un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-06-16_18,2022-06-16_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 adultscore=0 clxscore=1015 suspectscore=0 phishscore=0 spamscore=0 impostorscore=0 mlxlogscore=999 lowpriorityscore=0 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2206160084 X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Jun 2022 21:14:02 -0000 GDB developers: Ping? Just wondering if anyone has had a chance to look at this patch. Carl ----------------------------- On Thu, 2022-06-09 at 14:04 +0100, Luis Machado wrote: > Sending as a clean new thread. > > v6: > - Fix misc typos and augment the commit message. > - Updated source file comments. > > v5: > - Updated test case comments on the purpose of the test. > - Add test to check system supports record-replay. > - Removed now unnecessary record test when activating record. > > v4: > - Updated testcase to make it a bit longer so it can exercise > reverse-stepping > multiple times. > - Cleaned up debugging prints. > > v3: > - Updated testcase. The format for writing the DWARF program body in > the > testcase expect file changed. > See commit gdb/testsuite/dwarf: simplify line number program syntax > (commit d4c4a2298cad06ca71cfef725f5248f68205f0be) > > v2: > - Check if both the line and symtab match for a particular line table > entry. > > -- > > When running GDB's testsuite on aarch64-linux/Ubuntu 20.04 (also > spotted on > the ppc backend), I noticed some failures in gdb.reverse/solib- > precsave.exp > and gdb.reverse/solib-reverse.exp. > > The failure happens around the following code: > > 38 b[1] = shr2(17); /* middle part two */ > 40 b[0] = 6; b[1] = 9; /* generic statement, end part two */ > 42 shr1 ("message 1\n"); /* shr1 one */ > > Normal execution: > > - step from line 38 will land on line 40. > - step from line 40 will land on line 42. > > Reverse execution: > > - step from line 42 will land on line 40. > - step from line 40 will land on line 40. > - step from line 40 will land on line 38. > > The problem here is that line 40 contains two contiguous but distinct > PC ranges in the line table, like so: > > Line 40 - [0x7ec ~ 0x7f4] > Line 40 - [0x7f4 ~ 0x7fc] > > The two distinct ranges are generated because GCC started outputting > source > column information, which GDB doesn't take into account at the > moment. > > These GCC changes came into effect with commits > 497b7c47042d542ae48d10badf0c3d0088f6f798 and > and 0029b929c9719a9794492915206314308fbdf03a. > > When stepping forward from line 40, we skip both of these ranges and > land on > line 42. When stepping backward from line 42, we stop at the start PC > of the > second (or first, going backwards) range of line 40. > > This happens because we have this check in > infrun.c:process_event_stop_test: > > /* When stepping backward, stop at beginning of line range > (unless it's the function entry point, in which case > keep going back to the call point). */ > CORE_ADDR stop_pc = ecs->event_thread->stop_pc (); > if (stop_pc == ecs->event_thread->control.step_range_start > && stop_pc != ecs->stop_func_start > && execution_direction == EXEC_REVERSE) > end_stepping_range (ecs); > else > keep_going (ecs); > > Since we've reached ecs->event_thread->control.step_range_start, we > stop > stepping backwards. > > The right thing to do is to look for adjacent PC ranges for the same > line, > until we notice a line change. Then we take that as the start PC of > the > range. > > Another solution I thought about is to merge the contiguous ranges > when > we are reading the line tables. Though I'm not sure if we really want > to process > that data as opposed to keeping it as the compiler created, and then > working > around that. > > In any case, the following patch addresses this problem. > > Validated on aarch64-linux and x86_64/Ubuntu 20.04/18.04. Carl Love > has > verified that it does fix a similar issue on ppc. > > Ubuntu 18.04 doesn't actually run into these failures because the > compiler > doesn't generate distinct PC ranges for the same line. > > I see similar failures on x86_64 in the gdb.reverse tests > (gdb.reverse/step-reverse.exp and gdb.reverse/step-reverse.exp). > Those are > also fixed by this patch. > > The included testcase (based on a test Carl wrote) exercises this > problem for > Arm, ppc and x86. It shows full passes with the patch applied. > > Co-authored-by: Carl Love > --- > gdb/infrun.c | 22 ++- > gdb/symtab.c | 49 ++++++ > gdb/symtab.h | 16 ++ > gdb/testsuite/gdb.reverse/map-to-same-line.c | 54 +++++++ > .../gdb.reverse/map-to-same-line.exp | 141 > ++++++++++++++++++ > 5 files changed, 281 insertions(+), 1 deletion(-) > create mode 100644 gdb/testsuite/gdb.reverse/map-to-same-line.c > create mode 100644 gdb/testsuite/gdb.reverse/map-to-same-line.exp > > diff --git a/gdb/infrun.c b/gdb/infrun.c > index 02c98b50c8c..e9e14e58745 100644 > --- a/gdb/infrun.c > +++ b/gdb/infrun.c > @@ -6917,11 +6917,31 @@ process_event_stop_test (struct > execution_control_state *ecs) > have software watchpoints). */ > ecs->event_thread->control.may_range_step = 1; > > + /* When we are stepping inside a particular line range, in > reverse, > + and we are sitting at the first address of that range, we need > to > + check if this address also shows up in another line range as > the > + end address. > + > + If so, we need to check what line such a step range points to. > + If it points to the same line as the current step range, that > + means we need to keep going in order to reach the first > address > + of the line range. We repeat this until we eventually get to > the > + first address of a particular line we're stepping through. */ > + CORE_ADDR range_start = ecs->event_thread- > >control.step_range_start; > + if (execution_direction == EXEC_REVERSE) > + { > + gdb::optional real_range_start > + = find_line_range_start (ecs->event_thread->stop_pc ()); > + > + if (real_range_start.has_value ()) > + range_start = *real_range_start; > + } > + > /* When stepping backward, stop at beginning of line range > (unless it's the function entry point, in which case > keep going back to the call point). */ > CORE_ADDR stop_pc = ecs->event_thread->stop_pc (); > - if (stop_pc == ecs->event_thread->control.step_range_start > + if (stop_pc == range_start > && stop_pc != ecs->stop_func_start > && execution_direction == EXEC_REVERSE) > end_stepping_range (ecs); > diff --git a/gdb/symtab.c b/gdb/symtab.c > index 8564986f66d..9625ad7aa8a 100644 > --- a/gdb/symtab.c > +++ b/gdb/symtab.c > @@ -3390,6 +3390,55 @@ find_pc_line (CORE_ADDR pc, int notcurrent) > return sal; > } > > +/* Compare two symtab_and_line entries. Return true if both have > + the same line number and the same symtab pointer. That means we > + are dealing with two entries from the same line and from the same > + source file. > + > + Return false otherwise. */ > + > +static bool > +sal_line_symtab_matches_p (const symtab_and_line &sal1, > + const symtab_and_line &sal2) > +{ > + return (sal1.line == sal2.line && sal1.symtab == sal2.symtab); > +} > + > +/* See symtah.h. */ > + > +gdb::optional > +find_line_range_start (CORE_ADDR pc) > +{ > + struct symtab_and_line current_sal = find_pc_line (pc, 0); > + > + if (current_sal.line == 0) > + return {}; > + > + struct symtab_and_line prev_sal = find_pc_line (current_sal.pc - > 1, 0); > + > + /* If the previous entry is for a different line, that means we > are already > + at the entry with the start PC for this line. */ > + if (!sal_line_symtab_matches_p (prev_sal, current_sal)) > + return current_sal.pc; > + > + /* Otherwise, keep looking for entries for the same line but with > + smaller PC's. */ > + bool done = false; > + CORE_ADDR prev_pc; > + while (!done) > + { > + prev_pc = prev_sal.pc; > + > + prev_sal = find_pc_line (prev_pc - 1, 0); > + > + /* Did we notice a line change? If so, we are done with the > search. */ > + if (!sal_line_symtab_matches_p (prev_sal, current_sal)) > + done = true; > + } > + > + return prev_pc; > +} > + > /* See symtab.h. */ > > struct symtab * > diff --git a/gdb/symtab.h b/gdb/symtab.h > index ac902a4cbbe..500faf7d93b 100644 > --- a/gdb/symtab.h > +++ b/gdb/symtab.h > @@ -2286,6 +2286,22 @@ extern struct symtab_and_line find_pc_line > (CORE_ADDR, int); > extern struct symtab_and_line find_pc_sect_line (CORE_ADDR, > struct obj_section *, > int); > > +/* Given PC, and assuming it is part of a range of addresses that is > part of a > + line, go back through the linetable and find the starting PC of > that > + line. > + > + For example, suppose we have 3 PC ranges for line X: > + > + Line X - [0x0 - 0x8] > + Line X - [0x8 - 0x10] > + Line X - [0x10 - 0x18] > + > + If we call the function with PC == 0x14, we want to return 0x0, > as that is > + the starting PC of line X, and the ranges are contiguous. > +*/ > + > +extern gdb::optional find_line_range_start (CORE_ADDR > pc); > + > /* Wrapper around find_pc_line to just return the symtab. */ > > extern struct symtab *find_pc_line_symtab (CORE_ADDR); > diff --git a/gdb/testsuite/gdb.reverse/map-to-same-line.c > b/gdb/testsuite/gdb.reverse/map-to-same-line.c > new file mode 100644 > index 00000000000..89a1898bdc2 > --- /dev/null > +++ b/gdb/testsuite/gdb.reverse/map-to-same-line.c > @@ -0,0 +1,54 @@ > +/* Copyright 2022 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 < > http://www.gnu.org/licenses/ > >. */ > + > +/* This source file provides dummy code that is only meant to force > the > + compiler to generate instructions for the various labels. The > TAG markers > + are used by the testcase to generate DWARF information and line > tables. */ > + > +int > +main () > +{ /* TAG: main prologue */ > + asm ("main_label: .globl main_label"); > + int i = 1, j = 2, k; > + float f1 = 2.0, f2 = 4.1, f3; > + const char *str_1 = "foo", *str_2 = "bar", *str_3; > + > + asm ("line1: .globl line1"); > + k = i; f3 = f1; str_3 = str_1; /* TAG: line 1 */ > + > + asm ("line2: .globl line2"); > + k = j; f3 = f2; str_3 = str_2; /* TAG: line 2 */ > + > + asm ("line3: .globl line3"); > + k = i; f3 = f1; str_3 = str_1; /* TAG: line 3 */ > + > + asm ("line4: .globl line4"); > + k = j; f3 = f2; str_3 = str_2; /* TAG: line 4 */ > + > + asm ("line5: .globl line5"); > + k = i; f3 = f1; str_3 = str_1; /* TAG: line 5 */ > + > + asm ("line6: .globl line6"); > + k = j; f3 = f2; str_3 = str_2; /* TAG: line 6 */ > + > + asm ("line7: .globl line7"); > + k = i; f3 = f1; str_3 = str_1; /* TAG: line 7 */ > + > + asm ("line8: .globl line8"); > + k = j; f3 = f2; str_3 = str_2; /* TAG: line 8 */ > + > + asm ("main_return: .globl main_return"); > + return 0; /* TAG: main return */ > +} > diff --git a/gdb/testsuite/gdb.reverse/map-to-same-line.exp > b/gdb/testsuite/gdb.reverse/map-to-same-line.exp > new file mode 100644 > index 00000000000..fd958ba114b > --- /dev/null > +++ b/gdb/testsuite/gdb.reverse/map-to-same-line.exp > @@ -0,0 +1,141 @@ > +# Copyright 2022 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 < > http://www.gnu.org/licenses/ > >. > + > +# When stepping (forwards or backwards), GDB should step over the > entire line > +# and not just a particular entry in the line table. This test was > added to > +# verify the find_line_range_start function properly sets the step > range for a > +# line that consists of multiple statements, i.e. multiple entries > in the line > +# table. This test creates a DWARF line table that contains > multiple entries > +# for the same line to do the needed testing. > + > +load_lib dwarf.exp > + > +# This test can only be run on targets which support DWARF-2 and use > gas. > +if {![dwarf2_support]} { > + unsupported "dwarf2 support required for this test" > + return 0 > +} > + > +if [get_compiler_info] { > + return -1 > +} > + > +# The DWARF assembler requires the gcc compiler. > +if {!$gcc_compiled} { > + unsupported "gcc is required for this test" > + return 0 > +} > + > +# This test suitable only for process record-replay > +if ![supports_process_record] { > + return > +} > + > +standard_testfile .c .S > + > +if { [prepare_for_testing "failed to prepare" ${testfile} > ${srcfile}] } { > + return -1 > +} > + > +set asm_file [standard_output_file $srcfile2] > +Dwarf::assemble $asm_file { > + global srcdir subdir srcfile > + declare_labels integer_label L > + > + # Find start address and length of program > + lassign [function_range main [list > ${srcdir}/${subdir}/$srcfile]] \ > + main_start main_len > + set main_end "$main_start + $main_len" > + > + cu {} { > + compile_unit { > + {language @DW_LANG_C} > + {name map-to-same-line.c} > + {stmt_list $L DW_FORM_sec_offset} > + {low_pc 0 addr} > + } { > + subprogram { > + {external 1 flag} > + {name main} > + {low_pc $main_start addr} > + {high_pc $main_len DW_FORM_data4} > + } > + } > + } > + > + lines {version 2 default_is_stmt 1} L { > + include_dir "${srcdir}/${subdir}" > + file_name "$srcfile" 1 > + > + # Generate the line table program with distinct source lines > being > + # mapped to the same line entry. Line 1, 5 and 8 contain 1 > statement > + # each. Line 2 contains 2 statements. Line 3 contains 3 > statements. > + program { > + DW_LNE_set_address $main_start > + line [gdb_get_line_number "TAG: main prologue"] > + DW_LNS_copy > + DW_LNE_set_address line1 > + line [gdb_get_line_number "TAG: line 1" ] > + DW_LNS_copy > + DW_LNE_set_address line2 > + line [gdb_get_line_number "TAG: line 2" ] > + DW_LNS_copy > + DW_LNE_set_address line3 > + line [gdb_get_line_number "TAG: line 2" ] > + DW_LNS_copy > + DW_LNE_set_address line4 > + line [gdb_get_line_number "TAG: line 3" ] > + DW_LNS_copy > + DW_LNE_set_address line5 > + line [gdb_get_line_number "TAG: line 3" ] > + DW_LNS_copy > + DW_LNE_set_address line6 > + line [gdb_get_line_number "TAG: line 3" ] > + DW_LNS_copy > + DW_LNE_set_address line7 > + line [gdb_get_line_number "TAG: line 5" ] > + DW_LNS_copy > + DW_LNE_set_address line8 > + line [gdb_get_line_number "TAG: line 8" ] > + DW_LNS_copy > + DW_LNE_set_address main_return > + line [gdb_get_line_number "TAG: main return"] > + DW_LNS_copy > + DW_LNE_end_sequence > + } > + } > +} > + > +if { [prepare_for_testing "failed to prepare" ${testfile} \ > + [list $srcfile $asm_file] {nodebug} ] } { > + return -1 > +} > + > +if ![runto_main] { > + return -1 > +} > + > +# Activate process record/replay > +gdb_test_no_output "record" "turn on process record" > + > +gdb_test "tbreak main_return" "Temporary breakpoint .*" "breakpoint > at return" > +gdb_test "continue" "Temporary breakpoint .*" "run to end of main" > + > +# At this point, GDB has already recorded the execution up until the > return > +# statement. Reverse-step and test if GDB transitions between lines > in the > +# expected order. It should reverse-step across lines 8, 5, 3, 2 > and 1. > +foreach line {8 5 3 2 1} { > + gdb_test "reverse-step" ".*TAG: line $line.*" "reverse step to > line $line" > +}