diff options
Diffstat (limited to 'Documentation/fujitsu/frv/gdbstub.txt')
| -rw-r--r-- | Documentation/fujitsu/frv/gdbstub.txt | 130 |
1 files changed, 0 insertions, 130 deletions
diff --git a/Documentation/fujitsu/frv/gdbstub.txt b/Documentation/fujitsu/frv/gdbstub.txt deleted file mode 100644 index b92bfd902a4e..000000000000 --- a/Documentation/fujitsu/frv/gdbstub.txt +++ /dev/null @@ -1,130 +0,0 @@ - ==================== - DEBUGGING FR-V LINUX - ==================== - - -The kernel contains a GDB stub that talks GDB remote protocol across a serial -port. This permits GDB to single step through the kernel, set breakpoints and -trap exceptions that happen in kernel space and interrupt execution. It also -permits the NMI interrupt button or serial port events to jump the kernel into -the debugger. - -On the CPUs that have on-chip UARTs (FR400, FR403, FR405, FR555), the -GDB stub hijacks a serial port for its own purposes, and makes it -generate level 15 interrupts (NMI). The kernel proper cannot see the serial -port in question under these conditions. - -On the MB93091-VDK CPU boards, the GDB stub uses UART1, which would otherwise -be /dev/ttyS1. On the MB93093-PDK, the GDB stub uses UART0. Therefore, on the -PDK there is no externally accessible serial port and the serial port to -which the touch screen is attached becomes /dev/ttyS0. - -Note that the GDB stub runs entirely within CPU debug mode, and so should not -incur any exceptions or interrupts whilst it is active. In particular, note -that the clock will lose time since it is implemented in software. - - -================== -KERNEL PREPARATION -================== - -Firstly, a debuggable kernel must be built. To do this, unpack the kernel tree -and copy the configuration that you wish to use to .config. Then reconfigure -the following things on the "Kernel Hacking" tab: - - (*) "Include debugging information" - - Set this to "Y". This causes all C and Assembly files to be compiled - to include debugging information. - - (*) "In-kernel GDB stub" - - Set this to "Y". This causes the GDB stub to be compiled into the - kernel. - - (*) "Immediate activation" - - Set this to "Y" if you want the GDB stub to activate as soon as possible - and wait for GDB to connect. This allows you to start tracing right from - the beginning of start_kernel() in init/main.c. - - (*) "Console through GDB stub" - - Set this to "Y" if you wish to be able to use "console=gdb0" on the - command line. That tells the kernel to pass system console messages to - GDB (which then prints them on its standard output). This is useful when - debugging the serial drivers that'd otherwise be used to pass console - messages to the outside world. - -Then build as usual, download to the board and execute. Note that if -"Immediate activation" was selected, then the kernel will wait for GDB to -attach. If not, then the kernel will boot immediately and GDB will have to -interrupt it or wait for an exception to occur before doing anything with -the kernel. - - -========================= -KERNEL DEBUGGING WITH GDB -========================= - -Set the serial port on the computer that's going to run GDB to the appropriate -baud rate. Assuming the board's debug port is connected to ttyS0/COM1 on the -computer doing the debugging: - - stty -F /dev/ttyS0 115200 - -Then start GDB in the base of the kernel tree: - - frv-uclinux-gdb linux [uClinux] - -Or: - - frv-uclinux-gdb vmlinux [MMU linux] - -When the prompt appears: - - GNU gdb frv-031024 - Copyright 2003 Free Software Foundation, Inc. - GDB is free software, covered by the GNU General Public License, and you are - welcome to change it and/or distribute copies of it under certain conditions. - Type "show copying" to see the conditions. - There is absolutely no warranty for GDB. Type "show warranty" for details. - This GDB was configured as "--host=i686-pc-linux-gnu --target=frv-uclinux"... - (gdb) - -Attach to the board like this: - - (gdb) target remote /dev/ttyS0 - Remote debugging using /dev/ttyS0 - start_kernel () at init/main.c:395 - (gdb) - -This should show the appropriate lines from the source too. The kernel can -then be debugged almost as if it's any other program. - - -=============================== -INTERRUPTING THE RUNNING KERNEL -=============================== - -The kernel can be interrupted whilst it is running, causing a jump back to the -GDB stub and the debugger: - - (*) Pressing Ctrl-C in GDB. This will cause GDB to try and interrupt the - kernel by sending an RS232 BREAK over the serial line to the GDB - stub. This will (mostly) immediately interrupt the kernel and return it - to the debugger. - - (*) Pressing the NMI button on the board will also cause a jump into the - debugger. - - (*) Setting a software breakpoint. This sets a break instruction at the - desired location which the GDB stub then traps the exception for. - - (*) Setting a hardware breakpoint. The GDB stub is capable of using the IBAR - and DBAR registers to assist debugging. - -Furthermore, the GDB stub will intercept a number of exceptions automatically -if they are caused by kernel execution. It will also intercept BUG() macro -invocation. - |