forked from Imagelibrary/rtems
152 lines
7.7 KiB
Plaintext
152 lines
7.7 KiB
Plaintext
/*****************************************************/
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Debugged this stub against the MongooseV bsp. Relies on putting break
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instructions on breakpoints and step targets- normal stuff, and does not
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employ hardware breakpoint support at this time. As written, a single
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breakpoint in a loop will not be reasserted unless the user steps or has
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a 2nd one, since breakpoints are only reset when the gdb stub is
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re-entered. A useful enhancement would be to fix the break instruction
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management so the stub could invisibly put a 2nd break after the 1st
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"official" one so it can silently reset breakpoints. Shouldn't be too
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hard, mostly a matter of working it out.
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This was tested only against an R3000 MIPS. It should work OK on a
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R4000. Needs to be tested at some point.
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This stub supports threads as implemented by gdb 5 and doesn't have any
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bugs I'm aware of.
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Greg Menke
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3/5/2002
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/*****************************************************/
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The contents of this directory are based upon the "r46kstub.tar.gz" package
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released to the net by
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C. M. Heard
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VVNET, Inc. phone: +1 408 247 9376
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4040 Moorpark Ave. Suite 206 fax: +1 408 244 3651
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San Jose, CA 95117 USA e-mail: heard@vvnet.com
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This package was released in the September 1996 time frame for use
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with gdb 4.16 and an IDT R4600 Orion. The stub was modified to support
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R3000 class CPUs and to work within the mips-rtems exeception processing
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framework.
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THe file memlimits.h could end up being target board dependent. If
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this is the case, copy it to your BSP directory and modify as necessary.
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--joel
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8 February 2002
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Original README
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===============
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The r46kstub directory and its compressed archive (r46kstub.tar.gz) contain
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the 9/29/96 source code snapshot for a ROM-resident gdb-4.16 debug agent
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(aka stub) for the IDT R4600 Orion processor. It is based on the stub for
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the Hitachi SH processor written by Ben Lee and Steve Chamberlain and
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supplied with the gdb-4.16 distribution; that stub in turn was "originally
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based on an m68k software stub written by Glenn Engel at HP, but has changed
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quite a bit". The modifications for the R4600 were contributed by C. M.
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Heard of VVNET, Inc. and were based in part on the Algorithmics R4000 version
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of Phil Bunce's PMON program.
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The distribution consists of the following files:
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-rw-r--r-- 1 1178 Sep 29 16:34 ChangeLog
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-rw-r--r-- 1 748 Jul 26 01:18 Makefile
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-rw-r--r-- 1 6652 Sep 29 16:34 README
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-rw-r--r-- 1 1829 May 21 02:02 gdb_if.h
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-rw-r--r-- 1 3745 Sep 29 14:03 ioaddr.h
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-rw-r--r-- 1 2906 Sep 29 14:39 limits.h
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-rw-r--r-- 1 6552 May 23 00:17 mips_opcode.h
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-rw-r--r-- 1 14017 May 21 02:04 r4600.h
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-rw-r--r-- 1 23874 Jul 21 20:31 r46kstub.c
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-rw-r--r-- 1 1064 Jul 3 12:35 r46kstub.ld
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-rw-r--r-- 1 13299 Sep 29 16:24 stubinit.S
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With the exception of mips_opcode.h, which is a slightly modified version
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of a header file contributed by Ralph Campbell to 4.4 BSD and is therefore
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copyrighted by the UC Regents, all of the source files have been dedicated
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by their authors to the public domain. Use them as you wish, but do so
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at your own risk! The authors accept _no_ responsibility for any errors.
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The debug agent contained herein is at this writing in active use at VVNET
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supporting initial hardware debug and board bring-up of an OC-12 ATM probe
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board. It uses polled I/O on a 16C450 UART. We had originally intended to
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add support for interrupts to allow gdb to break in on a running program,
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but we have found that this is not really necessary since the reset button
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will accomplish the same purpose (thanks to the MIPS feature of saving the
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program counter in the ErrorEPC register when a reset exception occurs).
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Be aware that this stub handles ALL interrupts and exceptions except for
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reset (or NMI) in the same way -- by passing control to the debug command
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loop. It of course uses the ROM exception vectors to do so. In order to
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support code that actally needs to use interrupts we use use a more elaborate
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stub that is linked with the downloaded program. It hooks the RAM exception
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vectors and clears the BEV status bit to gain control. The ROM-based stub
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is still used in this case for initial program loading.
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In order to port this stub to a different platform you will at a minimum
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need to customize the macros in limits.h (which define the limits of readable,
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writeable, and steppable address space) and the I/O addresses in ioaddr.h
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(which define the 16C450 MMIO addresses). If you use something other than
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a 16C450 UART you will probably also need to modify the portions of stubinit.S
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which deal with the serial port. I've tried to be careful to respect all the
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architecturally-defined hazards as described in Appendix F of Kane and
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Heinrich, MIPS RISC Architecture, in order to minimize the work in porting
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to 4000-series processors other than the R4600, but no guarantees are offered.
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Support is presently restricted to big-endian addressing, and I've not even
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considered what changes would be needed for little-endian support.
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When this stub is built with gcc-2.7.2 and binutils-2.6 you will see a few
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warning messages from the single-step support routine where a cast is used
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to sign-extend a pointer (the next instruction address) into a long long
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(the PC image). Those warnings are expected; I've checked the generated
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code and it is doing what I had intended. But you should not see any other
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warnings or errors. Here is a log of the build:
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mips64orion-idt-elf-gcc -g -Wa,-ahld -Wall -membedded-data \
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-O3 -c r46kstub.c >r46kstub.L
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r46kstub.c: In function `doSStep':
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r46kstub.c:537: warning: cast to pointer from integer of different size
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r46kstub.c:539: warning: cast to pointer from integer of different size
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r46kstub.c:547: warning: cast to pointer from integer of different size
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r46kstub.c:561: warning: cast to pointer from integer of different size
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r46kstub.c:563: warning: cast to pointer from integer of different size
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r46kstub.c:572: warning: cast to pointer from integer of different size
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r46kstub.c:574: warning: cast to pointer from integer of different size
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r46kstub.c:582: warning: cast to pointer from integer of different size
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r46kstub.c:589: warning: cast to pointer from integer of different size
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r46kstub.c:591: warning: cast to pointer from integer of different size
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r46kstub.c:597: warning: cast to pointer from integer of different size
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r46kstub.c:599: warning: cast to pointer from integer of different size
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r46kstub.c:605: warning: cast to pointer from integer of different size
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r46kstub.c:607: warning: cast to pointer from integer of different size
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r46kstub.c:613: warning: cast to pointer from integer of different size
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r46kstub.c:615: warning: cast to pointer from integer of different size
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r46kstub.c:624: warning: cast to pointer from integer of different size
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r46kstub.c:628: warning: cast to pointer from integer of different size
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r46kstub.c:635: warning: cast to pointer from integer of different size
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r46kstub.c:637: warning: cast to pointer from integer of different size
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mips64orion-idt-elf-gcc -g -Wa,-ahld -Wall -membedded-data \
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-O3 -c stubinit.S >stubinit.L
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mips64orion-idt-elf-ld -t -s -T r46kstub.ld -Map r46kstub.map -o r46kstub.out
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mips64orion-idt-elf-ld: mode elf32bmip
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stubinit.o
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r46kstub.o
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mips64orion-idt-elf-objcopy -S -R .bss -R .data -R .reginfo \
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-O srec r46kstub.out r46kstub.hex
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Limitations: stubinit.S deliberately forces the PC (which is a 64-bit
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register) to contain a legitimate sign-extended 32-bit value. This was
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done to cope with a bug in gdb-4.16, which does _not_ properly sign-extend
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the initial PC when it loads a program. This means that you cannot use
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the "set" command to load an unmapped sixty-four bit virtual address into
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the PC, as you can for all other registers.
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Please send bug reports, comments, or suggestions for improvement to:
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