Based on kernel version 2.6.27. Page generated on 2008-10-13 09:53 EST.
1 A Simple Guide to Configure KGDB 2 3 Sonic Zhang <sonic.zhang[AT]analog[DOT]com> 4 Aug. 24th 2006 5 6 7 This KGDB patch enables the kernel developer to do source level debugging on 8 the kernel for the Blackfin architecture. The debugging works over either the 9 ethernet interface or one of the uarts. Both software breakpoints and 10 hardware breakpoints are supported in this version. 11 http://docs.blackfin.uclinux.org/doku.php?id=kgdb 12 13 14 2 known issues: 15 1. This bug: 16 http://blackfin.uclinux.org/tracker/index.php?func=detail&aid=544&group_id=18&atid=145 17 The GDB client for Blackfin uClinux causes incorrect values of local 18 variables to be displayed when the user breaks the running of kernel in GDB. 19 2. Because of a hardware bug in Blackfin 533 v1.0.3: 20 05000067 - Watchpoints (Hardware Breakpoints) are not supported 21 Hardware breakpoints cannot be set properly. 22 23 24 Debug over Ethernet: 25 26 1. Compile and install the cross platform version of gdb for blackfin, which 27 can be found at $(BINROOT)/bfin-elf-gdb. 28 29 2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under 30 "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb". 31 With this selected, option "Full Symbolic/Source Debugging support" and 32 "Compile the kernel with frame pointers" are also selected. 33 34 3. Select option "KGDB: connect over (Ethernet)". Add "kgdboe=@target-IP/,@host-IP/" to 35 the option "Compiled-in Kernel Boot Parameter" under "Kernel hacking". 36 37 4. Connect minicom to the serial port and boot the kernel image. 38 39 5. Configure the IP "/> ifconfig eth0 target-IP" 40 41 6. Start GDB client "bfin-elf-gdb vmlinux". 42 43 7. Connect to the target "(gdb) target remote udp:target-IP:6443". 44 45 8. Set software breakpoint "(gdb) break sys_open". 46 47 9. Continue "(gdb) c". 48 49 10. Run ls in the target console "/> ls". 50 51 11. Breakpoint hits. "Breakpoint 1: sys_open(..." 52 53 12. Display local variables and function paramters. 54 (*) This operation gives wrong results, see known issue 1. 55 56 13. Single stepping "(gdb) si". 57 58 14. Remove breakpoint 1. "(gdb) del 1" 59 60 15. Set hardware breakpoint "(gdb) hbreak sys_open". 61 62 16. Continue "(gdb) c". 63 64 17. Run ls in the target console "/> ls". 65 66 18. Hardware breakpoint hits. "Breakpoint 1: sys_open(...". 67 (*) This hardware breakpoint will not be hit, see known issue 2. 68 69 19. Continue "(gdb) c". 70 71 20. Interrupt the target in GDB "Ctrl+C". 72 73 21. Detach from the target "(gdb) detach". 74 75 22. Exit GDB "(gdb) quit". 76 77 78 Debug over the UART: 79 80 1. Compile and install the cross platform version of gdb for blackfin, which 81 can be found at $(BINROOT)/bfin-elf-gdb. 82 83 2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under 84 "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb". 85 With this selected, option "Full Symbolic/Source Debugging support" and 86 "Compile the kernel with frame pointers" are also selected. 87 88 3. Select option "KGDB: connect over (UART)". Set "KGDB: UART port number" to be 89 a different one from the console. Don't forget to change the mode of 90 blackfin serial driver to PIO. Otherwise kgdb works incorrectly on UART. 91 92 4. If you want connect to kgdb when the kernel boots, enable 93 "KGDB: Wait for gdb connection early" 94 95 5. Compile kernel. 96 97 6. Connect minicom to the serial port of the console and boot the kernel image. 98 99 7. Start GDB client "bfin-elf-gdb vmlinux". 100 101 8. Set the baud rate in GDB "(gdb) set remotebaud 57600". 102 103 9. Connect to the target on the second serial port "(gdb) target remote /dev/ttyS1". 104 105 10. Set software breakpoint "(gdb) break sys_open". 106 107 11. Continue "(gdb) c". 108 109 12. Run ls in the target console "/> ls". 110 111 13. A breakpoint is hit. "Breakpoint 1: sys_open(..." 112 113 14. All other operations are the same as that in KGDB over Ethernet. 114 115 116 Debug over the same UART as console: 117 118 1. Compile and install the cross platform version of gdb for blackfin, which 119 can be found at $(BINROOT)/bfin-elf-gdb. 120 121 2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under 122 "Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb". 123 With this selected, option "Full Symbolic/Source Debugging support" and 124 "Compile the kernel with frame pointers" are also selected. 125 126 3. Select option "KGDB: connect over UART". Set "KGDB: UART port number" to console. 127 Don't forget to change the mode of blackfin serial driver to PIO. 128 Otherwise kgdb works incorrectly on UART. 129 130 4. If you want connect to kgdb when the kernel boots, enable 131 "KGDB: Wait for gdb connection early" 132 133 5. Connect minicom to the serial port and boot the kernel image. 134 135 6. (Optional) Ask target to wait for gdb connection by entering Ctrl+A. In minicom, you should enter Ctrl+A+A. 136 137 7. Start GDB client "bfin-elf-gdb vmlinux". 138 139 8. Set the baud rate in GDB "(gdb) set remotebaud 57600". 140 141 9. Connect to the target "(gdb) target remote /dev/ttyS0". 142 143 10. Set software breakpoint "(gdb) break sys_open". 144 145 11. Continue "(gdb) c". Then enter Ctrl+C twice to stop GDB connection. 146 147 12. Run ls in the target console "/> ls". Dummy string can be seen on the console. 148 149 13. Then connect the gdb to target again. "(gdb) target remote /dev/ttyS0". 150 Now you will find a breakpoint is hit. "Breakpoint 1: sys_open(..." 151 152 14. All other operations are the same as that in KGDB over Ethernet. The only 153 difference is that after continue command in GDB, please stop GDB 154 connection by 2 "Ctrl+C"s and connect again after breakpoints are hit or 155 Ctrl+A is entered.