Debugging the OpenRISC 1000 with gdb
Contents
1. 1 Gu zvimes Ivan 226 cd is ped beoe Pole iude ida 1 H Hello World example seseeees li 32 I Igor MohOotrz 22c rer EPERPRPIR Rete RE 3 info registers command for OpenRISC 1000 1 info spr eommand i224 esf eb Ren 1 5 info spr command example 9 info spr command argument specification 5 info spr command complete group 5 info spr command single register 5 Iyan G zVIBeX x saad ee kerri toan a erai 1 J Jeremy Bennett 015 eiua De Ee pe ekian 1 Johan Rydyerg lesser ease eed oedena neds i DUA Gis Acar oie ued faite Nm LL 1 JTAG OpenRISC 1000 interface 1 JTAG remote connection robustness 15 JTAG robustness or remote interface 4 jtag target lel dep RE Re padebiwa gins yh AER 1 K known problems bRRERRE p RIDES 15 known problems architectural compatability 15 known problems Orlksim architectural simulator re ee ee E E 15 known problems remote JTAG connection TFOWUSUNESS 1 utes ren dire coe buit rri ecd 15 known problems watchpoints 15 L Linux kernel example 0000 i Linux kernel example 00005 11 Linux kernel initial program counter t2 Linux kernel loading Luusse 11 Linux kernel symbol file 11 Linux kernel symbolic debugging virtual memory PEIPER aha dace ap ites to ea 132. 9 11 R remote JTAG connection robustness 15 remote OpenRISC 1000 target connecting 3 remote program loading example 9c 11 remote program restart cosi eee 10 remote program stall sssssssss 10 remote program termination sess 10 Remote Serial Protocol suuuus 4 remote target jtag command 3 remote target jtag command example 9 11 remote target specification 3 remote target specification example 9 14 remote target specification same machine 3 Reporting bugs e Det ere Re 15 TeSel iios SB Loa hehe REPRE Eee eee he ke GAS 4 resetting the target 00 c ee eee eens 4 restart remote program s sr nn 10 robustness OpenRISC remote JTAG interface 4 BHSPAIe SLOLPUIPLEI DU UNUM ieee leks 4 run command example sessesses 9 running the remote program 9 Rydvergs Johan eese eR RR eteni lisa 1 Appendix B Index S set command example sssussss 10 Special Purpose Registers 000 1 uu PTT 1 spi command 2 25 2enhreenkm PR Rex ne m Re 1 5 spr command argument specification 5 stall remote program 00006 10 step command example sseessss 10 SUMMALY eere i Eiee E te pr EA QE NES 1 symbol file loading sestre Terrats iren insent Es 8 symbol file Linux kernel
3. Ll symbolic debugging Linux kernel virtual memory 13 symbols when remote debugging 8 T target JAG peed bs ironiaa tae hs 1 target jtag command oco poer es 3 target jtag command direct 3 target jtag command direct testing 3 33 target jtag command local 3 target jtag command local testing 3 target jtag command remote 3 target jtag command remote example 9 TI target resebi l m ge i kibeni nni Ei Deiri 4 target specification direct 0 0 3 target specification local 0 3 target specification remote 4 3 target specification remote example 9 11 target specification same machine 3 target direct OpenRISC 1000 connecting 3 target local OpenRISC 1000 connecting 3 target OpenRISC 1000 connecting 3 target remote OpenRISC 1000 connecting 3 V virtual memory Linux kernel debugging 13 Z Zioinkowski Chris 4 222 be Sawa cet res 1 34 Debugging the OpenRISC 1000 with GDB The body of this manual is set in cmrl0 at 10 95pt with headings in cmb10 at 10 95pt and examples in cmtt10 at 10 95pt cmti10 at 10 95pt cmb10 at 10 95pt and cmsl10 at 10 95pt are used for emphasis
4. home jeremy svntrunk GNU gdb 6 8 linux_debug cfg WARNING config Unknown section tick ignoring WARNING config Unknown section pic ignoring Building automata done num uncovered 0 213 Parsing operands data done JTAG Proxy server started on port 50000 WARNING Unable to open RX file stream Resetting memory controller Resetting PIC If using the configuration suggested on the OpenCores website or the Embecosm appli cation note this will open up a xterm to be used as the Linux console In a separate terminal start GDB use the file command to get the symbols connect to the target via JTAG and load the Linux image or32 uclinux gdb Building automata done num uncovered 0 216 Parsing operands data done GNU gdb 6 8 Copyright C 2008 Free Software Foundation Inc License GPLv3 GNU GPL version 3 or later http gnu org licenses gpl html This is free software you are free to change and redistribute it There is NO WARRANTY to the extent permitted by law Type show copying and show warranty for details 12 Debugging the OpenRISC 1000 with GDB This GDB was configured as host i686 pc linux gnu target or32 uclinux gdb file vmlinux Reading symbols from home jeremy projects openrisc linux 2 6 19 vmlinux done gdb target jtag jtag localhost 50000 esp4 fini at net ipv4 esp4 c 466 466 if xfrm unregister type amp esp type AF INET lt 0 gdb load vmlinux Loading
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9. local OpenRISC 1000 target connecting 3 local target jtag command 3 local target specification 00 3 M Mark Minat 2 25 sai dae otis mae eae Bad be 1 Mimar Mark eR RE seed etd idee 1 Mohor Igor 4 45 see dite tds aang ies Mamas Hers 3 OpenRISC 1000 Architectural Simulator 4 OpenRISC 1000 Architectural Simulator Config uratlon xen dee Sosa edad 8 11 OpenRISC 1000 Architectural Simulator patch 4 OpenRISC 1000 JTAG interface il OpenRISC 1000 specific commands 1 Debugging the OpenRISC 1000 with GDB OpenRISC 1000 target connecting 3 OpenRISC 1000 target direct connecting 3 OpenRISC 1000 target local connecting 3 OpenRISC 1000 target remote connecting 3 OpenRISC 1000 custom commands 5 OpenRISC 1000 known GDB problems 15 Orlksim c m Rb S emcee ere EA 4 Orlksim bugs fixed 20005 15 Orlksim configuration 04 S 1l Orlksim patch 20i einu e raene Enni ni RM 4 OVERVIEW s rn e a See E EEE 1 P patch OpenRISC 1000 Architectural Simulator 4 patch Orks se iib Ib REN eae BRS 4 Per Bothheru iie E ERR bra x epe 1 program counter default for Linux kernel T2 program counter resetting 12 program loading i oped die dees eee beaded 9 program loading example 9 11 program loading remote
10. section text size 0x227d74 lma Oxf0000000 Loading section rodata size 0x23694 lma 0xf0228000 Loading section __param size 0x258 lma Oxf024b694 Loading section ex table size Oxbf8 lma Oxf024c000 Loading section data size 0x1950c lma Oxf024e000 Loading section data cacheline aligned size OxdO lma Oxf0267520 Loading section data init task size 0x2000 lma Oxf0268000 Loading section init text size Ox17018 lma Oxf026a000 Loading section init data size 0x704 lma 0xf0281018 Loading section init setup size Oxlec lma 0xf0281720 Loading section initcall init size 0x168 lma Oxf028190c Loading section con initcall init size Oxc lma Oxf0281a74 Loading section init ramfs size 0x2000 lma Oxf0282000 Loading section initrd size 0x200000 lma 0xf0284000 Start address Oxc0000000 load size 4723376 Transfer rate 25068 KB sec 337384 bytes write gdb Using run at this point will not work since loading the Linux kernel has specified an entry point 0xc0000000 at the start of the ROM image gdb x i pc 0xc0000000 1 j OxO gdb This can be corrected and then the program will run gdb set pc 0x100 gdb run Starting program home jeremy projects openrisc linux 2 6 19 vmlinux The initial message will appear on the console output xterm as Linux copies itself from ROM to main memory Copying Linux Ok booting the kernel Little else appears for some time since the serial driver is not yet initialized However the terminal runn
11. the extent permitted by law Type show copying and show warranty for details This GDB was configured as host i686 pc linux gnu target or32 uclinux gdb file hello Reading symbols from home jeremy svntrunk GNU gdb 6 8 progs_or32 hello done gdb The connection to the target the architectural simulator is then established using the port number given in the configuration file gdb target jtag jtag localhost 50000 0x00000104 in start gdb The program of interest can now be loaded gdb load hello Loading section text size 0x1290 lma OxO Loading section rodata size Oxe lma 0x1290 Start address Ox100 load size 4766 Transfer rate 38128 bits in 1 sec 2383 bytes write gdb The program does not immediately start running since on opening the connection to the target GDB stalls the processor via the JTAG interface All the GDB commands including the SPR commands are available For example gdb bt 40 0x00000104 in _start gdb info spr 0 17 SYS SR SPRO_17 32769 0x8001 gdb The Supervision Register shows the target is in Supervisor Mode and that SPRs have User Mode read access Note The supervision register is used to provide the value for the GDB ps processor status variable so can also be accessed as gdb print ps 1 32769 gdb For this example set a breakpoint at the start of main and then run the program gdb break main Breakpoint 1 at 0x1264 file hello c line 41 gdb run Star
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14. value Set exception enable bit Jump to main routine Enable exceptions DELAY SLOT a org OxFFC l nop Guarantee the exception vector space does not have general purpose code This is compiled and linked with the OpenRISC 1000 GNU toolchain Note that the linking must specify the bootloader first and use the Ttext OxO argument The Orlksim architectural simulator is configured with memory starting at location 0x0 The debugging interface is enabled by using a debug section section debug enabled ES 1 gdb enabled 1 server_port 50000 end The architectural simulator is started in its own terminal window If the configuration is in debug cfg then the command might be or32 uclinux sim f debug cfg Reading script file from debug cfg Building automata done num uncovered 0 213 Parsing operands data done JTAG Proxy server started on port 50000 Resetting PIC Note that no program is specified that will be loaded from GDB In a separate window start up GDB or32 uclinux gdb A local copy of the symbol table is needed specified with the file command Building automata done num uncovered 0 216 Parsing operands data done GNU gdb 6 8 Copyright C 2008 Free Software Foundation Inc License GPLv3 GNU GPL version 3 or later http gnu org licenses gpl html Chapter 3 Small and Large Examples This is free software you are free to change and redistribute it There is NO WARRANTY to
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16. 00 with GDB Chapter 3 Small and Large Examples 7 3 Small and Large Examples Two examples are given 1 A simple Hello World program what else to show the basics 2 Linux 2 6 19 kernel as an example of a large program Both use the OpenRISC 1000 architectural simulator Orlksim 3 1 A Hello World program This is the cannonical small program Here is the main program and its two subprograms added to demonstrate a meaningful backtrace void level2 simexit O void level1 level2 main int i int j simputs Hello World n leveliO It is linked with a program providing the utility functions simexit simputc and simprints void simexit int rc asm _volatile Ed EN Ntl nopNtAO K NOP EXIT simexit void simputc int c 1 asm volatile Ntl nopNtAO K NOP_PUTC 2 simputc void simputs char str 1 int i for i 0 str i NO i 8 Debugging the OpenRISC 1000 with GDB simputc int str il simputs Finally a small bootloader is needed which will be placed at the OpenRISC reset vector location 0x100 to set up a stack and jump to the main program org 0x100 The reset routine goes at 0x100 global _start start addi r1 r0 0x7f00 addi r2 r1 0x0 mfspr r3 r0 17 OFT r3 r3 0x10 jal main mtspr r0 r3 17 Set SP to value OxT7f00 FP and SP are the same Get SR
17. 891696 When execution exits by execution of a 1 nop 1 the connection to the target is auto matically broken However it is perfectly possible to re establish a connection to the target either in the current GDB session or in a separate session If the session is new the symbols will need to be reloaded with the file command Re establish the connection using the remote jtag command gdb target jtag jtag localhost 50000 Chapter 3 Small and Large Examples 11 Program exited normally gdb The connection is re established Since the last instruction executed was 1 nop 1 GDB reports that the program executed normally To rerun the program the program counter must be placed somewhere appropriate The reset vector 0x100 is appropriate and the program can then be rerun gdb set pc 0x100 gdb run Starting program home jeremy svntrunk GNU gdb 6 8 progs_or32 hello Program exited normally gdb 3 2 Linux 2 6 19 Kernel Boot In this example a Linux 2 6 19 Kernel is booted under control of GDB The kernel should be built using the OpenRISC 1000 toolchain as described on the OpenCores website www opencores org or Embecosm Application Note 2 www embecosm com download html Once again the target is the Orlksim architectural simulator Start the architectural simulator with a configuration suitable for Linux and with de bugging enabled on port 50000 or32 uclinux sim f linux debug cfg Reading script file from
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19. Debugging the OpenRISC 1000 with GDB Target Processor Manual First Edition for GDB version 6 8 Jeremy Bennett Embecosm Limited Please report bugs using the OpenCores tracker www opencores org ptracker cgi list orik Debugging the OpenRISC 1000 with GDB TTEXinfo 2004 02 19 09 Copyright 2008 Embecosm Limited Published by Embecosm Limited 68 Hambledon Road Bournemouth BH7 6PJ UK Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 3 or any later version published by the Free Software Foundation with the Front Cover Texts being Debugging the OpenRISC 1000 with GDB by Jeremy Bennett and with the Back Cover Texts being You are free to copy and modify this Manual Table of Contents Summary of GDB with OpenRISC 1000 1 Contributors to GDB for the OpenRISC 1000 1 1 Connecting to an OpenRISC 1000 Target 3 1 1 Direct connection via a JTAG JP1 Interface s esses 3 1 2 Connection via the OpenRISC 1000 Remote JTAG Interface 3 2 Commands just for the OpenRISC 1000 9 2 1 Using the info spr Command esseseeleeee esses 5 2 20 Using the spr Command 0 0 cece eee eens 5 3 Small and Large Examples 7 3 1 A Hello World program 00 cece eee eee eee eens 7 3 2 Linux 2 6 19 Kernel Boot 0 00 e eee 11 4 Known Problems
20. G r if Debug interface types 22200 3 direct OpenRISC 1000 target connecting 3 direct target jtag command 3 direct target specification lisse lesse 3 E BEimb6cOSr ssie teie Dess bcepbei bai 1 exampl 5 22eberRRERsRIexbR epe tr 7 examples breakpoint command 9 examples bt command 9 10 examples continue command 10 examples Hello World lusus 7 examples info spr command 9 examples Lin x oc cause sees T examples Linux kernel suus 11 examples Linux kernel loading 11 examples program loading 9 examples remote target jtag command 9 3E examples remote target specification 9 TI examples run command 00005 9 examples running a program 9 examples set command 000 5 10 examples step command 04 10 examples symbol file loading 8 F FDL GNU Free Documentation License 23 Forin Alessandro 00 ainne nni hi 1 GDB 5 3 differences in port of GDB version 6 8 H 15 GDB interface OpenRISC 1000 1 EdbUul uidi bebe Tias tee ARE 1 graphical debugging 00 2 0 ee eee il graphical debugging ddd il graphical debugging gdbtui
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25. gh referred to as the remote interface the target may actually be on the same machine just running in a separate process with its own terminal window For example to connect to the OpenRISC 1000 Architectural simulator which is running on machine thomas and has been configured to talk to GDB on port 50000 I could use the command target jtag jtag thomas 50000 The target machine is specified after the jtag and separated from the target port by a colon If the architectural simulator was running on the same machine just locahost would suffice as the machine name thus target jtag jtag localhost 50000 Unfortunately there are now two different flavours of the J TAG interface used with OpenRISC 1000 The original version was created for use with the OpenRISC 1000 System on Chip ORPSoC A new smaller and simpler JTAG interface was developed by Igor Mohor in 2004 which is used on some designs The default behavior of GDB is to use the original ORPSoC version of the interface for backwards compatibility GDB can use the Igor Mohor version by specifying for example 4 Debugging the OpenRISC 1000 with GDB target jtag jtag mohor localhost 50000 This interface is only available with remote JTAG connections since all modern interfaces are based on the remote connection For completeness target jtag jtag orpsoc localhost 50000 is provided as a synonym for target jtag jtag localhost 50000 By default establishing a connecti
26. gisters command will show the 32 general purpose registers while the info registers all command will add the program counter supervision register and exception program counter register Throughout this document user input is emphasised like this input program output is show like this Hello World For those who like their debugging graphical the gdbtui command is available typically as or32 uclinux gdbtui GDB for OpenRISC 1000 can also be run under ddd as follows ddd debugger or32 uclinux gdb gdb Contributors to GDB for the OpenRISC 1000 The pantheon of contributors to GDB over the years is recorded in the main user manual Debugging with GDB The GNU Source Level Debugger There is no official history of contributors to the OpenRISC 1000 version However the current author believes the original GDB 5 0 and 5 3 ports were the work of e Ivan Guzvinec and Johan Rydverg at OpenCores who wrote the Binary File Descriptor library e Alessandro Forin at Carnegie Mellon University and Per Bothner at the University of Wisconsin who wrote the main GDB interface and e Mark Mlinar at Cygnus Support and Chris Ziomkowski at ASICS ws who wrote the OpenRISC JTAG interface The port to GDB 6 8 is the work of Jeremy Bennett of Embecosm Limited jeremy bennett embecosm com Plea If you know of anyone who has been omitted from this list please email the current author so the omission can be corrected and credit given where it is d
27. he title year new authors and publisher of the Modified Version as given on the Title Page If there is no section Entitled History in the Docu ment create one stating the title year authors and publisher of the Document as given on its Title Page then add an item describing the Modified Version as stated in the previous sentence Preserve the network location if any given in the Document for public access to a Transparent copy of the Document and likewise the network locations given in the Document for previous versions it was based on These may be placed in the History section You may omit a network location for a work that was published at least four years before the Document itself or if the original publisher of the version it refers to gives permission For any section Entitled Acknowledgements or Dedications Preserve the Title of the section and preserve in the section all the substance and tone of each of the contributor acknowledgements and or dedications given therein Preserve all the Invariant Sections of the Document unaltered in their text and in their titles Section numbers or the equivalent are not considered part of the section titles Delete any section Entitled Endorsements Such a section may not be included in the Modified Version Do not retitle any existing section to be Entitled Endorsements or to conflict in title with any Invariant Section Preserve any Warranty Disclaime
28. hris Ziomkowski 2 22 eene 1 commands breakpoint example 9 commands bt example 9 10 commands continue example 10 commands info registers for OpenRISC 1000 1 commands info spr 00 eee 1 5 commands info spr example 9 commands OpenRISC 1000 specific 1 commands run example 005 9 commands set example 02 00 10 commands SDE i09 p RPPEETYS 1 commands spr command 0005 5 commands step example usesesue 10 commands target jtag 00000000 3 commands target jtag direct 3 commands target jtag direct testing 3 commands target jtag local 3 commands target jtag local testing 3 commands target jtag remote 3 commands target jtag remote example 9 1 configuration OpenRISC 1000 Architectural Oimulator LeIcleeeqeeereBlewpRE ees 8 11 configuration Orlksim 04 8 11 connecting OpenRISC 1000 target 3 connecting OpenRISC 1000 target direct 3 connecting OpenRISC 1000 target local 3 connecting OpenRISC 1000 target remote 3 continue command example 10 contributors OpenRISC 1000 I contributors unknown sees 1 custom commands OpenRISC 1000 5 3l D CO
29. ief idea of what it does Copyright C year name of author 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 2 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 write to the Free Software Foundation Inc 51 Franklin Street Fifth Floor Boston MA 02110 1301 USA Also add information on how to contact you by electronic and paper mail If the program is interactive make it output a short notice like this when it starts in an interactive mode Gnomovision version 69 Copyright C year name of author Gnomovision comes with ABSOLUTELY NO WARRANTY for details type show w This is free software and you are welcome to redistribute it under certain conditions type show c for details The hypothetical commands show w and show c should show the appropriate parts of the General Public License Of course the commands you use may be called something other than show w and show c they could even be mouse clicks or menu items whatever suits you
30. ing distributing or modifying the Program or works based on it 20 6 10 Debugging the OpenRISC 1000 with GDB Each time you redistribute the Program or any work based on the Program the recipient automatically receives a license from the original licensor to copy distribute or modify the Program subject to these terms and conditions You may not impose any further restrictions on the recipients exercise of the rights granted herein You are not responsible for enforcing compliance by third parties to this License If as a consequence of a court judgment or allegation of patent infringement or for any other reason not limited to patent issues conditions are imposed on you whether by court order agreement or otherwise that contradict the conditions of this License they do not excuse you from the conditions of this License If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations then as a consequence you may not distribute the Program at all For example if a patent license would not permit royalty free redistribution of the Program by all those who receive copies directly or indirectly through you then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program If any portion of this section is held invalid or unenforceable under any particular circumstance the balance of the section is intended
31. ing the architectural simulator will be reflecting the progress Resetting PIC Copying Linux Ok booting the kernel doleololelelelelelelelelelelelelee counters reset oook kk kkk kkk cycles 340441616 insn 29500690 dokelelolelelelelelelelelelelelelee counters reset eb KKK lt 5 gt Linux version 2 6 19 or32 jeremy thomas gcc version 3 4 4 3 Sat Jun 28 19 30 0 Chapter 3 Small and Large Examples Detecting Processor units Signed 0x391 Setting up paging and PTEs write protecting ro sections 0xc0002000 0xc024c000 Setting up identical mapping 0x80000000 0x90000000 Setting up identical mapping 0x92000000 0x92002000 Setting up identical mapping 0xb8070000 0xb8072000 Setting up identical mapping 0x97000000 0x97002000 Setting up identical mapping 0x99000000 0x9a000000 Setting up identical mapping 0x93000000 0x93002000 Setting up identical mapping 0xa6000000 0xa6100000 13 Setting up identical mapping 0x1e50000 Ox1fa0000 lt 7 gt 0n node 0 totalpages 3968 lt 7 gt DMA zone O pages used for memmap lt 7 gt Normal zone 15 pages used for memmap lt 7 gt Normal zone 3953 pages LIFO batch 0 dtlb_miss_handler itlb_miss_handler Built 1 zonelists lt 5 gt Kernel command c00040c8 c00041a8 Total pages 3953 line root dev ram console ttySO Eventually the serial port driver is initialized and the Linux console xterm will show the Linux output eventually giving the console promp
32. ividual copies of this License in the various documents with a single copy that is included in the collection provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects You may extract a single document from such a collection and distribute it individu ally under this License provided you insert a copy of this License into the extracted document and follow this License in all other respects regarding verbatim copying of that document 7 AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works in or on a volume of a storage or distribution medium is called 28 10 Debugging the OpenRISC 1000 with GDB an aggregate if the copyright resulting from the compilation is not used to limit the legal rights of the compilation s users beyond what the individual works permit When the Document is included in an aggregate this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document If the Cover Text requirement of section 3 is applicable to these copies of the Document then if the Document is less than one half of the entire aggregate the Document s Cover Texts may be placed on covers that bracket the Document within the aggregate or the electronic equivalent of covers if the Document is in electronic form Otherwise they must appear
33. kr t ewe 15 Appendix A GNU GENERAL PUBLIC EIC EENSB 2 a uu ce a CREER 17 Prearble acere ep GR Rese dg OPI Sed eager ten rains Iy TERMS AND CONDITIONS FOR COPYING DISTRIBUTION AND MODIFICATION 4 18 How to Apply These Terms to Your New Programs 22 Appendix B GNU Free Documentation License TE 23 B 1 ADDENDUM How to use this License for your documents 29 Debugging the OpenRISC 1000 with GDB Summary of GDB with OpenRISC 1000 GDB is described well in its user manual Debugging with GDB The GNU Source Level Debugger This manual describes how to use GDB to debug C programs cross compiled for and running on processors using the OpenRISC 1000 architecture In general GDB does not run on the actual target but on a separate host processor It communicates with the target via a custom remote protocol which drives the JTAG interface on the OpenRISC 1000 This is provided by adding a special target jtag to GDB allowing the debugger to connect via the JTAG interface See Chapter 1 Connecting to the Target page 3 In addition the info command is extended to allow inspection of OpenRISC 1000 Special Purpose registers and a new command spr is added to set the value of a Special Purpose Register See Chapter 2 OpenRISC 1000 Specific Commands page 5 All the normal GDB commands should work although hardware watchpoints are not tested at present The info re
34. may differ in detail to address new problems or concerns Each version is given a distinguishing version number If the Program specifies a version number of this License which applies to it and any later version you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation If the Program does not specify a version number of this License you may choose any version ever published by the Free Software Foundation If you wish to incorporate parts of the Program into other free programs whose distri bution conditions are different write to the author to ask for permission For software Appendix A GNU GENERAL PUBLIC LICENSE 21 11 12 which is copyrighted by the Free Software Foundation write to the Free Software Foun dation we sometimes make exceptions for this Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally NO WARRANTY BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE THERE IS NO WARRANTY FOR THE PROGRAM TO THE EXTENT PERMITTED BY APPLI CABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPY RIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE PROGRAM AS IS WITHOUT WARRANTY OF ANY KIND EITHER EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MER CHANTABILITY AND FITNESS FOR A PARTI
35. ng the Document or a portion of it either copied verbatim or with modifications and or translated into another language A Secondary Section is a named appendix or a front matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document s overall subject or to related matters and contains nothing that could fall directly within that overall subject Thus if the Document is in part a textbook of mathematics a Secondary Section may not explain any mathematics The relationship could be a matter of historical connection with the subject or with related matters or of legal commercial philosophical ethical or political position regarding them The Invariant Sections are certain Secondary Sections whose titles are designated as being those of Invariant Sections in the notice that says that the Document is released 24 Debugging the OpenRISC 1000 with GDB under this License If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant The Document may contain zero Invariant Sections If the Document does not identify any Invariant Sections then there are none The Cover Texts are certain short passages of text that are listed as Front Cover Texts or Back Cover Texts in the notice that says that the Document is released under this License A Front Cover Text may be at most 5 words and a Back Cover Text m
36. o Back Cover Texts A copy of the license is included in the section entitled GNU Free Documentation License If you have Invariant Sections Front Cover Texts and Back Cover Texts replace the with Texts line with this with the Invariant Sections being list their titles with the Front Cover Texts being list and with the Back Cover Texts being list If you have Invariant Sections without Cover Texts or some other combination of the three merge those two alternatives to suit the situation If your document contains nontrivial examples of program code we recommend releasing these examples in parallel under your choice of free software license such as the GNU General Public License to permit their use in free software 30 Debugging the OpenRISC 1000 with GDB Appendix B Index Index A Alessandro Forin 0 000 cece cence eee il B Bennett Jeremy si nebere ber wey Y heeds 1 BED inier tecenpeudag Mates aman te ees 1 Binary File Description library 1 Bothner Peri cheesy heed erence seb ue 1 breakpoint command example 9 bt command example sssss 9 10 BUGS csc tei ERPPREURIORP eee eae ree ented de 15 bugs architectural compatibility 15 bugs Orlksim architectural simulator 15 bugs remote JTAG connection robustness 15 B gs reporting 1l ges centrine UPPER RP 15 bugs watchpoints 0 eee eee eee 15 C C
37. on does not reset the target This allows debugging to resume a partially complete program on connection If a reset is required the keyworkd RESET case insensitive may be added at the end of the target command For example target jtag jtag localhost 50000 reset Warning GDB version 6 8 requires a patch to the architectural simulator This should be available on the OpenCores website or contact the author directly Warning The OpenRISC remote JTAG interface is not particularly robust In particu lar dropping and reconnecting sessions does not seem to work well Eventually this interface will be replaced by the generic GDB Remote Serial Interface Chapter 2 Commands just for the OpenRISC 1000 5 2 Commands just for the OpenRISC 1000 The OpenRISC 1000 has one particular feature that is difficult for GDB GDB models target processors with a register bank and a block of memory The internals of GDB assume that there are not a huge number of registers in total The OpenRISC 1000 Special Purpose Registers SPR do not really fit well into this structure There are too many of them 12 groups each with 2000 entries so far with up to 32 groups permitted to be implemented as ordinary registers in GDB Think what this would mean for the command info registers all However they cannot be considered memory since they do not reside in the main memory map The solution is to add two new commands to GDB to see the value of a particular SPR and
38. on printed covers that bracket the whole aggregate TRANSLATION Iranslation is considered a kind of modification so you may distribute translations of the Document under the terms of section 4 Replacing Invariant Sections with translations requires special permission from their copyright holders but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections You may include a translation of this License and all the license notices in the Document and any Warranty Disclaimers provided that you also include the original English version of this License and the original versions of those notices and disclaimers In case of a disagreement between the translation and the original version of this License or a notice or disclaimer the original version will prevail If a section in the Document is Entitled Acknowledgements Dedications or His tory the requirement section 4 to Preserve its Title section 1 will typically require changing the actual title TERMINATION You may not copy modify sublicense or distribute the Document except as expressly provided for under this License Any other attempt to copy modify sublicense or distribute the Document is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their licenses terminated so long as s
39. problems with the current implementation l If the OpenRISC 1000 Architecture supports hardware watchpoints GDB will use them to implement hardware breakpoints and watchpoints GDB is not perfect in handling of watchpoints It is possible to allocate hardware watchpoints and not discover until running that sufficient watchpoints are not available It is also possible that GDB will report watchpoints being hit spuriously This can be down to the assembly code having additional memory accesses that are not obviously reflected in the source code The remote JTAG connection is not robust to being interrupted or reconnecting If the connection is lost due to error then you must restart GDB and the target server for example the Orlksim architectural simulator Moving to the Remote Serial Protocol is intended to remedy this problem in the future The OpenRISC 1000 architecture has evolved since the port of GDB 5 3 in 2001 In particular the structure of the Unit Present register has changed and the CPU Configuration register has been added The port of GDB version 6 8 uses the current specification of the OpenRISC 1000 This means that old clients that talk to the debugger may not work In particular the Orlksim Architectural simulator requires a patch to work The handling of watchpoints in the Orlksim architectural simulator was incorrect To work with GDB 6 8 a patch is required to fix this problem This is combined with the patch changing the s
40. r program You should also get your employer if you work as a programmer or your school if any to sign a copyright disclaimer for the program if necessary Here is a sample alter the names Yoyodyne Inc hereby disclaims all copyright interest in the program Gnomovision which makes passes at compilers written by James Hacker signature of Ty Coon 1 April 1989 Ty Coon President of Vice This General Public License does not permit incorporating your program into proprietary programs If your program is a subroutine library you may consider it more useful to permit linking proprietary applications with the library If this is what you want to do use the GNU Library General Public License instead of this License Appendix B GNU Free Documentation License 23 Appendix B GNU Free Documentation License Version 1 2 November 2002 Copyright c 2000 2001 2002 Free Software Foundation Inc 51 Franklin Street Fifth Floor Boston MA 02110 1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed 0 PREAMBLE The purpose of this License is to make a manual textbook or other functional and useful document free in the sense of freedom to assure everyone the effective freedom to copy and redistribute it with or without modifying it either commercially or non commercially Secondarily this License preserves for the author and publisher a way to
41. rs If the Modified Version includes new front matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document you may at your option designate some or all of these sections as invariant To do this add their titles to the list of Invariant Sections in the Modified Version s license notice These titles must be distinct from any other section titles Appendix B GNU Free Documentation License 27 You may add a section Entitled Endorsements provided it contains nothing but endorsements of your Modified Version by various parties for example statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard You may add a passage of up to five words as a Front Cover Text and a passage of up to 25 words as a Back Cover Text to the end of the list of Cover Texts in the Modified Version Only one passage of Front Cover Text and one of Back Cover Text may be added by or through arrangements made by any one entity If the Document already includes a cover text for the same cover previously added by you or by arrangement made by the same entity you are acting on behalf of you may not add another but you may replace the old one on explicit permission from the previous publisher that added the old one The author s and publisher s of the Document do not by this License give permission to use their names for publicity for or to as
42. sert or imply endorsement of any Modified Version 5 COMBINING DOCUMENTS You may combine the Document with other documents released under this License under the terms defined in section 4 above for modified versions provided that you include in the combination all of the Invariant Sections of all of the original documents unmodified and list them all as Invariant Sections of your combined work in its license notice and that you preserve all their Warranty Disclaimers The combined work need only contain one copy of this License and multiple identical Invariant Sections may be replaced with a single copy If there are multiple Invariant Sections with the same name but different contents make the title of each such section unique by adding at the end of it in parentheses the name of the original author or publisher of that section if known or else a unique number Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work In the combination you must combine any sections Entitled History in the vari ous original documents forming one section Entitled History likewise combine any sections Entitled Acknowledgements and any sections Entitled Dedications You must delete all sections Entitled Endorsements 6 COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents released under this License and replace the ind
43. t VFS Mounted root ext2 filesystem readonly Freeing unused kernel memory 104k freed init started init started Starting pid 22 console dev ttySO etc init d rcS Please press Enter to activate this console Starting pid 25 console dev ttySO bin sh BusyBox v1 4 1 2007 03 22 18 53 56 EST Built in shell ash Enter help for a list of built in commands The full range of GDB debugging facilities are then available to debug the kernel BusyBox v1 4 1 2007 03 22 18 53 56 EST multi call binary BusyBox v1 4 1 2007 03 22 18 53 56 EST multi call binary Warning Linux is loaded into ROM at address Oxf0000000 then relocated by copy ing into main memory at adress 0x00000000 but with a virtual memory start address of 0xc0000000 as recorded in the image Plain GDB for OpenRISC 1000 is designed for bare metal debugging and does not cope well with the virtual memory and relocation in the Linux kernel In addition the architectural simulator does not handle virtual addresses read and written through the debug interface correctly Hardware breakpoints will work correctly they are not changed by copying but examining the data and restarting will 14 Debugging the OpenRISC 1000 with GDB fail For Linux kernel debugging KGDB should be used This is derived from GDB but at present a port for GDB 6 8 has not been completed Chapter 4 Known Problems 15 4 Known Problems There are some known
44. the scope of this License 3 You may copy and distribute the Program or a work based on it under Section 2 in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following a Accompany it with the complete corresponding machine readable source code which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or b Accompany it with a written offer valid for at least three years to give any third party for a charge no more than your cost of physically performing source distri bution a complete machine readable copy of the corresponding source code to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange or c Accompany it with the information you received as to the offer to distribute cor responding source code This alternative is allowed only for noncommercial dis tribution and only if you received the program in object code or executable form with such an offer in accord with Subsection b above The source code for a work means the preferred form of the work for making modifi cations to it For an executable work complete source code means all the source code for all modules it contains plus any associated interface definition files plus the scripts used to control compilation and installation of the executable However as a spe cial exception
45. the source code distributed need not include anything that is normally distributed in either source or binary form with the major components compiler kernel and so on of the operating system on which the executable runs unless that component itself accompanies the executable If distribution of executable or object code is made by offering access to copy from a designated place then offering equivalent access to copy the source code from the same place counts as distribution of the source code even though third parties are not compelled to copy the source along with the object code 4 You may not copy modify sublicense or distribute the Program except as expressly provided under this License Any attempt otherwise to copy modify sublicense or distribute the Program is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their licenses terminated so long as such parties remain in full compliance 5 You are not required to accept this License since you have not signed it However nothing else grants you permission to modify or distribute the Program or its derivative works These actions are prohibited by law if you do not accept this License Therefore by modifying or distributing the Program or any work based on the Program you indicate your acceptance of this License to do so and all its terms and conditions for copy
46. ting program home jeremy svntrunk GNU gdb 6 8 progs_or32 hello Switching to process 1 Breakpoint 1 main at hello c 44 41 simputs Hello World n gdb 10 Debugging the OpenRISC 1000 with GDB Note Since the connection is to the native code on the OpenRISC 1000 target there is no concept of a process number Thus process number 1 is used throughout It is now possible to step through the code gdb step simputs str 0x1290 Hello World n at utils c 90 90 for i 0 str i 0 i gdb step 91 simputc int str i gdb step 58 asm volatile tl nop t 0 K NOP_PUTC gdb At this point a backtrace will show where the code has reached gdb bt 0 simputc c 72 at utils c 58 41 0x00001icc in simputs str 0x1290 Hello World n at utils c 91 2 0x00001274 in main at hello c 41 3 0x00000118 in _start gdb One more step completes the call to the character output routine Inspecting the terminal running the Orlksim simulation shows the output appearing JTAG Proxy server started on port 50000 Resetting PIC H Let the program run to completion by giving GDB the continue command gdb cont Continuing Program exited normally gdb With completion of the program the terminal running Orlksim shows its final output Resetting PIC Hello World exit 0 reset cycles 0 insn 0 Qexit cycles 215892308 insn 14215891696 diff cycles 215892308 insn 14215
47. to set the value of a particular SPR 1 info spr is used to show the value of a SPR or group of SPRs 2 spr is used to set the value of an individual SPR 2 1 Using the info spr Command The value of an SPR is read by specifying either the unique name of the SPR or the its group and index in that group For example the Debug Reason Register DRR register 21 in group 6 Debug can be read using any of the following commands info spr DRR info spr debug DRR info spr debug 21 info spr 6 DRR info spr 6 21 In each case the output will be DEBUG DRR SPR6 21 O 0x0 It is also possible to inspect all the registers in a group For example to look at all the Programmable Interrupt Controller registers group 9 either of the following commands could be used info spr PIC info spr 9 And the output would be PIC PICMR SPR9_O O 0x9 PIC PICSR SPR9_2 O 0x8 Indicating that interrupts 0 and 4 are enabled and interrupt 4 is pending 2 2 Using the spr Command The value of an SPR is written by specifying the unique name of the SPR or its group and index in the same manner as for the info spr command An additional argument specifies the value to be written So for example the Programmable Interrupt Controller mask register could be changed to enable interrupts 5 and 3 only by any of the following commands spr PICMR 0x24 spr PIC PICMR 0x24 spr PIC 0 0x24 spr 9 PICMR 0x24 spr 9 2 0x24 Debugging the OpenRISC 10
48. tructure of the Unit Present and CPU Configuration registers The OpenRISC 1000 architecture uses its General Purpose Register GPR 2 as a frame pointer register However the fp variable in GDB is not currently implemented and will return the value of the stack pointer GPR 1 instead Reports of bugs are much welcomed Please report problems through the OpenCORES tracker at www opencores org ptracker cgi list orik 16 Debugging the OpenRISC 1000 with GDB Appendix A GNU GENERAL PUBLIC LICENSE Pr Appendix A GNU GENERAL PUBLIC LICENSE Version 2 June 1991 Copyright 1989 1991 Free Software Foundation Inc 51 Franklin Street Fifth Floor Boston MA 02110 1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed Preamble The licenses for most software are designed to take away your freedom to share and change it By contrast the GNU General Public License is intended to guarantee your freedom to share and change free software to make sure the software is free for all its users This General Public License applies to most of the Free Software Foundation s software and to any other program whose authors commit to using it Some other Free Software Foundation software is covered by the GNU Library General Public License instead You can apply it to your programs too When we speak of free software we are referring to freedom not price Our General
49. uch parties remain in full compliance FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new revised versions of the GNU Free Documentation License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns See http www gnu org copyleft Each version of the License is given a distinguishing version number If the Document specifies that a particular numbered version of this License or any later version applies to it you have the option of following the terms and conditions either of that specified version or of any later version that has been published not as a draft by the Free Software Foundation If the Document does not specify a version number of this License you may choose any version ever published not as a draft by the Free Software Foundation Appendix B GNU Free Documentation License 29 B 1 ADDENDUM How to use this License for your documents To use this License in a document you have written include a copy of the License in the document and put the following copyright and license notices just after the title page Copyright C year your name Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with no Invariant Sections no Front Cover Texts and n
50. ue Debugging the OpenRISC 1000 with GDB Chapter 1 Connecting to an OpenRISC 1000 Target 3 1 Connecting to an OpenRISC 1000 Target There are two ways to connect to an OpenRISC 1000 target with GDB 1 To hardware directly connected via a JP1 header linked to the parallel port 2 Via a TCP IP socket to a machine which has the hardware connected or is running the architectural simulator Both are achieved via the GDB command target jtag 1 1 Direct connection via a JTAG JP1 Interface In this case the the device to which the JP1 header is connected must be specifed to the target jtag command Typically that will be the parallel printer port so the command would be target jtag dev lp Warning The current author is not aware of anyone using the JP1 interface As a result this code has not been tested in the port to GDB version 6 8 Modern hardware connections are usually via interfaces such as USB for which the OpenRISC Remote Interface can be used see Section 1 2 Remote JTAG Connection page 3 1 2 Connection via the OpenRISC 1000 Remote JTAG Interface The more common mode of operation is through the OpenRISC 1000 Remote JTAG Inter face This communicates to the target through a TCP IP socket The target must then implement the client side of the interface to drive either physical hardware for example through a USB JTAG connector or a simulation of the hardware such as the OpenRISC Architectural Simulator Althou
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