path: root/arch/mips/kernel/gdb-stub.c

/*
 *  arch/mips/kernel/gdb-stub.c
 *
 *  Originally written by Glenn Engel, Lake Stevens Instrument Division
 *
 *  Contributed by HP Systems
 *
 *  Modified for SPARC by Stu Grossman, Cygnus Support.
 *
 *  Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
 *  Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
 *
 *  Copyright (C) 1995 Andreas Busse
 *
 *  Copyright (C) 2003 MontaVista Software Inc.
 *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
 */

/*
 *  To enable debugger support, two things need to happen.  One, a
 *  call to set_debug_traps() is necessary in order to allow any breakpoints
 *  or error conditions to be properly intercepted and reported to gdb.
 *  Two, a breakpoint needs to be generated to begin communication.  This
 *  is most easily accomplished by a call to breakpoint().  Breakpoint()
 *  simulates a breakpoint by executing a BREAK instruction.
 *
 *
 *    The following gdb commands are supported:
 *
 * command          function                               Return value
 *
 *    g             return the value of the CPU registers  hex data or ENN
 *    G             set the value of the CPU registers     OK or ENN
 *
 *    mAA..AA,LLLL  Read LLLL bytes at address AA..AA      hex data or ENN
 *    MAA..AA,LLLL: Write LLLL bytes at address AA.AA      OK or ENN
 *
 *    c             Resume at current address              SNN   ( signal NN)
 *    cAA..AA       Continue at address AA..AA             SNN
 *
 *    s             Step one instruction                   SNN
 *    sAA..AA       Step one instruction from AA..AA       SNN
 *
 *    k             kill
 *
 *    ?             What was the last sigval ?             SNN   (signal NN)
 *
 *    bBB..BB	    Set baud rate to BB..BB		   OK or BNN, then sets
 *							   baud rate
 *
 * All commands and responses are sent with a packet which includes a
 * checksum.  A packet consists of
 *
 * $<packet info>#<checksum>.
 *
 * where
 * <packet info> :: <characters representing the command or response>
 * <checksum>    :: < two hex digits computed as modulo 256 sum of <packetinfo>>
 *
 * When a packet is received, it is first acknowledged with either '+' or '-'.
 * '+' indicates a successful transfer.  '-' indicates a failed transfer.
 *
 * Example:
 *
 * Host:                  Reply:
 * $m0,10#2a               +$00010203040506070809101112131415#42
 *
 *
 *  ==============
 *  MORE EXAMPLES:
 *  ==============
 *
 *  For reference -- the following are the steps that one
 *  company took (RidgeRun Inc) to get remote gdb debugging
 *  going. In this scenario the host machine was a PC and the
 *  target platform was a Galileo EVB64120A MIPS evaluation
 *  board.
 *
 *  Step 1:
 *  First download gdb-5.0.tar.gz from the internet.
 *  and then build/install the package.
 *
 *  Example:
 *    $ tar zxf gdb-5.0.tar.gz
 *    $ cd gdb-5.0
 *    $ ./configure --target=mips-linux-elf
 *    $ make
 *    $ install
 *    $ which mips-linux-elf-gdb
 *    /usr/local/bin/mips-linux-elf-gdb
 *
 *  Step 2:
 *  Configure linux for remote debugging and build it.
 *
 *  Example:
 *    $ cd ~/linux
 *    $ make menuconfig <go to "Kernel Hacking" and turn on remote debugging>
 *    $ make
 *
 *  Step 3:
 *  Download the kernel to the remote target and start
 *  the kernel running. It will promptly halt and wait
 *  for the host gdb session to connect. It does this
 *  since the "Kernel Hacking" option has defined
 *  CONFIG_KGDB which in turn enables your calls
 *  to:
 *     set_debug_traps();
 *     breakpoint();
 *
 *  Step 4:
 *  Start the gdb session on the host.
 *
 *  Example:
 *    $ mips-linux-elf-gdb vmlinux
 *    (gdb) set remotebaud 115200
 *    (gdb) target remote /dev/ttyS1
 *    ...at this point you are connected to
 *       the remote target and can use gdb
 *       in the normal fasion. Setting
 *       breakpoints, single stepping,
 *       printing variables, etc.
 */
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/reboot.h>

#include <asm/asm.h>
#include <asm/cacheflush.h>
#include <asm/mipsregs.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/gdb-stub.h>
#include <asm/inst.h>
#include <asm/smp.h>

/*
 * external low-level support routines
 */

extern int putDebugChar(char c);    /* write a single character      */
extern char getDebugChar(void);     /* read and return a single char */
extern void trap_low(void);

/*
 * breakpoint and test functions
 */
extern void breakpoint(void);
extern void breakinst(void);
extern void async_breakpoint(void);
extern void async_breakinst(void);
extern void adel(void);

/*
 * local prototypes
 */

static void getpacket(char *buffer);
static void putpacket(char *buffer);
static int computeSignal(int tt);
static int hex(unsigned char ch);
static int hexToInt(char **ptr, int *intValue);
static int hexToLong(char **ptr, long *longValue);
static unsigned char *mem2hex(char *mem, char *buf, int count, int may_fault);
void handle_exception(struct gdb_regs *regs);

int kgdb_enabled;

/*
 * spin locks for smp case
 */
static DEFINE_SPINLOCK(kgdb_lock);
static raw_spinlock_t kgdb_cpulock[NR_CPUS] = {
	[0 ... NR_CPUS-1] = __RAW_SPIN_LOCK_UNLOCKED,
};

/*
 * BUFMAX defines the maximum number of characters in inbound/outbound buffers
 * at least NUMREGBYTES*2 are needed for register packets
 */
#define BUFMAX 2048

static char input_buffer[BUFMAX];
static char output_buffer[BUFMAX];
static int initialized;	/* !0 means we've been initialized */
static int kgdb_started;
static const char hexchars[]="0123456789abcdef";

/* Used to prevent crashes in memory access.  Note that they'll crash anyway if
   we haven't set up fault handlers yet... */
int kgdb_read_byte(unsigned char *address,