kgdb.c

linux内核源码

/*
 *  arch/cris/arch-v32/kernel/kgdb.c
 *
 *  CRIS v32 version by Orjan Friberg, Axis Communications AB.
 *
 *  S390 version
 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Denis Joseph Barrow ([e-mail],[e-mail]),
 *
 *  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 <[e-mail]>
 *
 *  Copyright (C) 1995 Andreas Busse
 */

/* FIXME: Check the documentation. */

/*
 *  kgdb usage notes:
 *  -----------------
 *
 * If you select CONFIG_ETRAX_KGDB in the configuration, the kernel will be
 * built with different gcc flags: "-g" is added to get debug infos, and
 * "-fomit-frame-pointer" is omitted to make debugging easier. Since the
 * resulting kernel will be quite big (approx. > 7 MB), it will be stripped
 * before compresion. Such a kernel will behave just as usually, except if
 * given a "debug=<device>" command line option. (Only serial devices are
 * allowed for <device>, i.e. no printers or the like; possible values are
 * machine depedend and are the same as for the usual debug device, the one
 * for logging kernel messages.) If that option is given and the device can be
 * initialized, the kernel will connect to the remote gdb in trap_init(). The
 * serial parameters are fixed to 8N1 and 115200 bps, for easyness of
 * implementation.
 *
 * To start a debugging session, start that gdb with the debugging kernel
 * image (the one with the symbols, vmlinux.debug) named on the command line.
 * This file will be used by gdb to get symbol and debugging infos about the
 * kernel. Next, select remote debug mode by
 *    target remote <device>
 * where <device> is the name of the serial device over which the debugged
 * machine is connected. Maybe you have to adjust the baud rate by
 *    set remotebaud <rate>
 * or also other parameters with stty:
 *    shell stty ... </dev/...
 * If the kernel to debug has already booted, it waited for gdb and now
 * connects, and you'll see a breakpoint being reported. If the kernel isn't
 * running yet, start it now. The order of gdb and the kernel doesn't matter.
 * Another thing worth knowing about in the getting-started phase is how to
 * debug the remote protocol itself. This is activated with
 *    set remotedebug 1
 * gdb will then print out each packet sent or received. You'll also get some
 * messages about the gdb stub on the console of the debugged machine.
 *
 * If all that works, you can use lots of the usual debugging techniques on
 * the kernel, e.g. inspecting and changing variables/memory, setting
 * breakpoints, single stepping and so on. It's also possible to interrupt the
 * debugged kernel by pressing C-c in gdb. Have fun! :-)
 *
 * The gdb stub is entered (and thus the remote gdb gets control) in the
 * following situations:
 *
 *  - If breakpoint() is called. This is just after kgdb initialization, or if
 *    a breakpoint() call has been put somewhere into the kernel source.
 *    (Breakpoints can of course also be set the usual way in gdb.)
 *    In eLinux, we call breakpoint() in init/main.c after IRQ initialization.
 *
 *  - If there is a kernel exception, i.e. bad_super_trap() or die_if_kernel()
 *    are entered. All the CPU exceptions are mapped to (more or less..., see
 *    the hard_trap_info array below) appropriate signal, which are reported
 *    to gdb. die_if_kernel() is usually called after some kind of access
 *    error and thus is reported as SIGSEGV.
 *
 *  - When panic() is called. This is reported as SIGABRT.
 *
 *  - If C-c is received over the serial line, which is treated as
 *    SIGINT.
 *
 * Of course, all these signals are just faked for gdb, since there is no
 * signal concept as such for the kernel. It also isn't possible --obviously--
 * to set signal handlers from inside gdb, or restart the kernel with a
 * signal.
 *
 * Current limitations:
 *
 *  - While the kernel is stopped, interrupts are disabled for safety reasons
 *    (i.e., variables not changing magically or the like). But this also
 *    means that the clock isn't running anymore, and that interrupts from the
 *    hardware may get lost/not be served in time. This can cause some device
 *    errors...
 *
 *  - When single-stepping, only one instruction of the current thread is
 *    executed, but interrupts are allowed for that time and will be serviced
 *    if pending. Be prepared for that.
 *
 *  - All debugging happens in kernel virtual address space. There's no way to
 *    access physical memory not mapped in kernel space, or to access user
 *    space. A way to work around this is using get_user_long & Co. in gdb
 *    expressions, but only for the current process.
 *
 *  - Interrupting the kernel only works if interrupts are currently allowed,
 *    and the interrupt of the serial line isn't blocked by some other means
 *    (IPL too high, disabled, ...)
 *
 *  - The gdb stub is currently not reentrant, i.e. errors that happen therein
 *    (e.g. accessing invalid memory) may not be caught correctly. This could
 *    be removed in future by introducing a stack of struct registers.
 *
 */

/*
 *  To enable debugger support, two things need to happen.  One, a
 *  call to kgdb_init() 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().
 *
 *    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
 *
 */


#include <linux/string.h>
#include <linux/signal.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/linkage.h>
#include <linux/reboot.h>

#include <asm/setup.h>
#include <asm/ptrace.h>

#include <asm/irq.h>
#include <asm/arch/hwregs/reg_map.h>
#include <asm/arch/hwregs/reg_rdwr.h>
#include <asm/arch/hwregs/intr_vect_defs.h>
#include <asm/arch/hwregs/ser_defs.h>

/* From entry.S. */
extern void gdb_handle_exception(void);
/* From kgdb_asm.S. */
extern void kgdb_handle_exception(void);

static int kgdb_started = 0;

/********************************* Register image ****************************/

typedef
struct register_image
{
	                      /* Offset */
	unsigned int   r0;    /* 0x00 */
	unsigned int   r1;    /* 0x04 */
	unsigned int   r2;    /* 0x08 */
	unsigned int   r3;    /* 0x0C */
	unsigned int   r4;    /* 0x10 */
	unsigned int   r5;    /* 0x14 */
	unsigned int   r6;    /* 0x18 */
	unsigned int   r7;    /* 0x1C */
	unsigned int   r8;    /* 0x20; Frame pointer (if any) */
	unsigned int   r9;    /* 0x24 */
	unsigned int   r10;   /* 0x28 */
	unsigned int   r11;   /* 0x2C */
	unsigned int   r12;   /* 0x30 */
	unsigned int   r13;   /* 0x34 */
	unsigned int   sp;    /* 0x38; R14, Stack pointer */
	unsigned int   acr;   /* 0x3C; R15, Address calculation register. */

	unsigned char  bz;    /* 0x40; P0, 8-bit zero register */
	unsigned char  vr;    /* 0x41; P1, Version register (8-bit) */
	unsigned int   pid;   /* 0x42; P2, Process ID */
	unsigned char  srs;   /* 0x46; P3, Support register select (8-bit) */
        unsigned short wz;    /* 0x47; P4, 16-bit zero register */
	unsigned int   exs;   /* 0x49; P5, Exception status */
	unsigned int   eda;   /* 0x4D; P6, Exception data address */
	unsigned int   mof;   /* 0x51; P7, Multiply overflow register */
	unsigned int   dz;    /* 0x55; P8, 32-bit zero register */
	unsigned int   ebp;   /* 0x59; P9, Exception base pointer */
	unsigned int   erp;   /* 0x5D; P10, Exception return pointer. Contains the PC we are interested in. */
	unsigned int   srp;   /* 0x61; P11, Subroutine return pointer */
	unsigned int   nrp;   /* 0x65; P12, NMI return pointer */
	unsigned int   ccs;   /* 0x69; P13, Condition code stack */
	unsigned int   usp;   /* 0x6D; P14, User mode stack pointer */
	unsigned int   spc;   /* 0x71; P15, Single step PC */
	unsigned int   pc;    /* 0x75; Pseudo register (for the most part set to ERP). */

} registers;

typedef
struct bp_register_image
{
	/* Support register bank 0. */
	unsigned int   s0_0;
	unsigned int   s1_0;
	unsigned int   s2_0;
	unsigned int   s3_0;
	unsigned int   s4_0;
	unsigned int   s5_0;
	unsigned int   s6_0;
	unsigned int   s7_0;
	unsigned int   s8_0;
	unsigned int   s9_0;
	unsigned int   s10_0;
	unsigned int   s11_0;
	unsigned int   s12_0;
	unsigned int   s13_0;
	unsigned int   s14_0;
	unsigned int   s15_0;

	/* Support register bank 1. */
	unsigned int   s0_1;
	unsigned int   s1_1;
	unsigned int   s2_1;
	unsigned int   s3_1;
	unsigned int   s4_1;
	unsigned int   s5_1;
	unsigned int   s6_1;
	unsigned int   s7_1;
	unsigned int   s8_1;
	unsigned int   s9_1;
	unsigned int   s10_1;
	unsigned int   s11_1;
	unsigned int   s12_1;
	unsigned int   s13_1;
	unsigned int   s14_1;
	unsigned int   s15_1;

	/* Support register bank 2. */
	unsigned int   s0_2;
	unsigned int   s1_2;
	unsigned int   s2_2;
	unsigned int   s3_2;
	unsigned int   s4_2;
	unsigned int   s5_2;
	unsigned int   s6_2;
	unsigned int   s7_2;
	unsigned int   s8_2;
	unsigned int   s9_2;
	unsigned int   s10_2;
	unsigned int   s11_2;
	unsigned int   s12_2;
	unsigned int   s13_2;
	unsigned int   s14_2;
	unsigned int   s15_2;

	/* Support register bank 3. */
	unsigned int   s0_3; /* BP_CTRL */
	unsigned int   s1_3; /* BP_I0_START */
	unsigned int   s2_3; /* BP_I0_END */
	unsigned int   s3_3; /* BP_D0_START */
	unsigned int   s4_3; /* BP_D0_END */
	unsigned int   s5_3; /* BP_D1_START */
	unsigned int   s6_3; /* BP_D1_END */
	unsigned int   s7_3; /* BP_D2_START */
	unsigned int   s8_3; /* BP_D2_END */
	unsigned int   s9_3; /* BP_D3_START */
	unsigned int   s10_3; /* BP_D3_END */
	unsigned int   s11_3; /* BP_D4_START */
	unsigned int   s12_3; /* BP_D4_END */
	unsigned int   s13_3; /* BP_D5_START */
	unsigned int   s14_3; /* BP_D5_END */
	unsigned int   s15_3; /* BP_RESERVED */

} support_registers;

enum register_name
{
	R0,  R1,  R2,  R3,
	R4,  R5,  R6,  R7,
	R8,  R9,  R10, R11,
	R12, R13, SP,  ACR,

	BZ,  VR,  PID, SRS,
	WZ,  EXS, EDA, MOF,
	DZ,  EBP, ERP, SRP,
	NRP, CCS, USP, SPC,
	PC,

	S0,  S1,  S2,  S3,
	S4,  S5,  S6,  S7,
	S8,  S9,  S10, S11,
	S12, S13, S14, S15

};

/* The register sizes of the registers in register_name. An unimplemented register
   is designated by size 0 in this array. */
static int register_size[] =
{
	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,

	1, 1, 4, 1,
	2, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,

	4,

	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4, 4,
	4, 4, 4

};

/* Contains the register image of the kernel.
   (Global so that they can be reached from assembler code.) */
registers reg;
support_registers sreg;

/************** Prototypes for local library functions ***********************/

/* Copy of strcpy from libc. */
static char *gdb_cris_strcpy(char *s1, const char *s2);

/* Copy of strlen from libc. */
static int gdb_cris_strlen(const char *s);

/* Copy of memchr from libc. */
static void *gdb_cris_memchr(const void *s, int c, int n);

/* Copy of strtol from libc. Does only support base 16. */
static int gdb_cris_strtol(const char *s, char **endptr, int base);

/********************** Prototypes for local functions. **********************/

/* Write a value to a specified register regno in the register image
   of the current thread. */
static int write_register(int regno, char *val);

/* Read a value from a specified register in the register image. Returns the
   status of the read operation. The register value is returned in valptr. */
static int read_register(char regno, unsigned int *valptr);

/* Serial port, reads one character. ETRAX 100 specific. from debugport.c */
int getDebugChar(void);

#ifdef CONFIG_ETRAXFS_SIM
int getDebugChar(void)
{
  return socketread();
}
#endif

/* Serial port, writes one character. ETRAX 100 specific. from debugport.c */
void putDebugChar(int val);

#ifdef CONFIG_ETRAXFS_SIM
void putDebugChar(int val)
{
  socketwrite((char *)&val, 1);
}
#endif

/* Returns the character equivalent of a nibble, bit 7, 6, 5, and 4 of a byte,
   represented by int x. */
static char highhex(int x);

/* Returns the character equivalent of a nibble, bit 3, 2, 1, and 0 of a byte,
   represented by int x. */
static char lowhex(int x);

/* Returns the integer equivalent of a hexadecimal character. */
static int hex(char ch);

/* Convert the memory, pointed to by mem into hexadecimal representation.
   Put the result in buf, and return a pointer to the last character
   in buf (null). */
static char *mem2hex(char *buf, unsigned char *mem, int count);