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step.cpp

/*
 *  linux/arch/arm/kernel/ptrace.c
 *
 *  By Ross Biro 1/23/92
 * edited by Linus Torvalds
 * ARM modifications Copyright (C) 2000 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/* Modified for use in jelie by cipix@iv.ro (2003)
 */

#include "jtagpxa250.h"
#include "stdio.h"

extern JTAGpxa250 *pxa250Ptr;



#define REG_PC  15
#define REG_PSR 16
//#define BREAKINST_ARM 0xef9f0001
#define BREAKINST_ARM   0xe1200070      /*bkpt #0*/
/* fill this in later */
#define BREAKINST_THUMB 0xdf00

#define predicate(x)    (x & 0xf0000000)
#define PREDICATE_ALWAYS        0xe0000000

#define PCMASK (0x3)

#define pc_pointer(v)  ((v) & ~PCMASK)

#define CC_C_BIT        (1 << 29)

typedef unsigned int u32;
typedef unsigned short u16;


union debug_insn {
        u32     arm;
        u16     thumb;
};

struct debug_entry {
        u32                     address;
        union debug_insn        insn;
};

struct debug_info {
        int                     nsaved;
        struct debug_entry      bp[2];
};


static inline unsigned int hweight16(unsigned int w)
{
unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
        res = (res & 0x3333) + ((res >> 2) & 0x3333);
        res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
        return (res & 0x00FF) + ((res >> 8) & 0x00FF);
}


/*
 * this routine will get a word off of the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline long get_user_reg(int offset)
{
        return pxa250Ptr->getSavePlace(offset);
}

/*
 * this routine will put a word on the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline int
put_user_reg(int offset, long data)
{
        pxa250Ptr->setSavePlace(offset,data);
        return 0;
}

static inline int
read_u32(unsigned long addr, u32 *res)
{
        int ret;

        if (addr & 0x3) {
                printf("FIXME: unalligned access not performed - returning crap\n");
        } else {
                pxa250Ptr->getData(addr, 1, res);
        }
        
        return 0;
}

static inline int
read_instr(unsigned long addr, u32 *res)
{
        int ret;
        u32 val;
        pxa250Ptr->getData(addr, 1, res);

        return 0;
}

/*
 * Get value of register `rn' (in the instruction)
 */
static unsigned long
jelie_getrn(unsigned long insn)
{
        unsigned int reg = (insn >> 16) & 15;
        unsigned long val;

        val = get_user_reg(reg);
        if (reg == 15)
                val = pc_pointer(val + 8);

        return val;
}

/*
 * Get value of operand 2 (in an ALU instruction)
 */
static unsigned long
jelie_getaluop2(unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        if (insn & 1 << 25) {
                val = insn & 255;
                shift = (insn >> 8) & 15;
                type = 3;
        } else {
                val = get_user_reg (insn & 15);

                if (insn & (1 << 4))
                        shift = (int)get_user_reg ((insn >> 8) & 15);
                else
                        shift = (insn >> 7) & 31;

                type = (insn >> 5) & 3;
        }

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

/*
 * Get value of operand 2 (in a LDR instruction)
 */
static unsigned long
jelie_getldrop2(unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        val = get_user_reg(insn & 15);
        shift = (insn >> 7) & 31;
        type = (insn >> 5) & 3;

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

#define OP_MASK 0x01e00000
#define OP_AND  0x00000000
#define OP_EOR  0x00200000
#define OP_SUB  0x00400000
#define OP_RSB  0x00600000
#define OP_ADD  0x00800000
#define OP_ADC  0x00a00000
#define OP_SBC  0x00c00000
#define OP_RSC  0x00e00000
#define OP_ORR  0x01800000
#define OP_MOV  0x01a00000
#define OP_BIC  0x01c00000
#define OP_MVN  0x01e00000

static unsigned long
get_branch_address(unsigned long pc, unsigned long insn)
{
        u32 alt = 0;

        switch (insn & 0x0e000000) {
        case 0x00000000:
        case 0x02000000: {
                /*
                 * data processing
                 */
                long aluop1, aluop2, ccbit;

                if ((insn & 0xf000) != 0xf000)
                        break;

                aluop1 = jelie_getrn(insn);
                aluop2 = jelie_getaluop2(insn);
                ccbit  = get_user_reg(REG_PSR) & CC_C_BIT ? 1 : 0;

                switch (insn & OP_MASK) {
                case OP_AND: alt = aluop1 & aluop2;             break;
                case OP_EOR: alt = aluop1 ^ aluop2;             break;
                case OP_SUB: alt = aluop1 - aluop2;             break;
                case OP_RSB: alt = aluop2 - aluop1;             break;
                case OP_ADD: alt = aluop1 + aluop2;             break;
                case OP_ADC: alt = aluop1 + aluop2 + ccbit;     break;
                case OP_SBC: alt = aluop1 - aluop2 + ccbit;     break;
                case OP_RSC: alt = aluop2 - aluop1 + ccbit;     break;
                case OP_ORR: alt = aluop1 | aluop2;             break;
                case OP_MOV: alt = aluop2;                      break;
                case OP_BIC: alt = aluop1 & ~aluop2;            break;
                case OP_MVN: alt = ~aluop2;                     break;
                }
                break;
        }

        case 0x04000000:
        case 0x06000000:
                /*
                 * ldr
                 */
                if ((insn & 0x0010f000) == 0x0010f000) {
                        unsigned long base;

                        base = jelie_getrn(insn);
                        if (insn & 1 << 24) {
                                long aluop2;

                                if (insn & 0x02000000)
                                        aluop2 = jelie_getldrop2( insn);
                                else
                                        aluop2 = insn & 0xfff;

                                if (insn & 1 << 23)
                                        base += aluop2;
                                else
                                        base -= aluop2;
                        }
                        if (read_u32(base, &alt) == 0)
                                alt = pc_pointer(alt);
                }
                break;

        case 0x08000000:
                /*
                 * ldm
                 */
                if ((insn & 0x00108000) == 0x00108000) {
                        unsigned long base;
                        int nr_regs;

                        if (insn & (1 << 23)) {
                                nr_regs = hweight16(insn & 65535) << 2;

                                if (!(insn & (1 << 24)))
                                        nr_regs -= 4;
                        } else {
                                if (insn & (1 << 24))
                                        nr_regs = -4;
                                else
                                        nr_regs = 0;
                        }

                        base = jelie_getrn(insn);

                        if (read_u32(base + nr_regs, &alt) == 0)
                                alt = pc_pointer(alt);
                        break;
                }
                break;

        case 0x0a000000: {
                /*
                 * bl or b
                 */
                signed long displ;
                /* It's a branch/branch link: instead of trying to
                 * figure out whether the branch will be taken or not,
                 * we'll put a breakpoint at both locations.  This is
                 * simpler, more reliable, and probably not a whole lot
                 * slower than the alternative approach of emulating the
                 * branch.
                 */
                displ = (insn & 0x00ffffff) << 8;
                displ = (displ >> 6) + 8;
                if (displ != 0 && displ != 4)
                        alt = pc + displ;
            }
            break;
        }

        return alt;
}

static int
swap_insn(unsigned long addr, void *old_insn, void *new_insn, int size)
{

        pxa250Ptr->getData(addr,1,(unsigned int *)old_insn);
        pxa250Ptr->putData(addr,1,(unsigned int *)new_insn);
        
        return 4;
}

static void
add_breakpoint(struct debug_info *dbg, unsigned long addr)
{
        int nr = dbg->nsaved;

        if (nr < 2) {
                u32 new_insn = BREAKINST_ARM;
                int res;

                res = swap_insn(addr, &dbg->bp[nr].insn, &new_insn, 4);

                if (res == 4) {
                        dbg->bp[nr].address = addr;
                        dbg->nsaved += 1;
                        printf("software breakpoint on at %x\n",addr);
                }
        } else
                printf("too many breakpoints\n");
}

/*
 * Clear one breakpoint in the user program.  We copy what the hardware
 * does and use bit 0 of the address to indicate whether this is a Thumb
 * breakpoint or an ARM breakpoint.
 */
static void clear_breakpoint(struct debug_entry *bp)
{
        unsigned long addr = bp->address;
        union debug_insn old_insn;
        int ret;

        printf("software breakpoint off at %x\n",addr);
        ret = swap_insn(addr, &old_insn.arm,
                                &bp->insn.arm, 4);

        if (ret != 4 || old_insn.arm != BREAKINST_ARM) {
                printf("corrupted ARM breakpoint at "
                                "0x%08lx (0x%08x)\n",addr, old_insn.arm);
        }
}

struct debug_info dbg_s, *dbg=&dbg_s;

void jelie_set_bpt()
{
        struct pt_regs *regs;
        unsigned long pc;
        u32 insn;
        int res;

        pc=get_user_reg(REG_PC);

        res = read_instr(pc, &insn);
        if (!res) {
                unsigned long alt;

                dbg->nsaved = 0;

                alt = get_branch_address(pc, insn);
                if (alt)
                        add_breakpoint(dbg, alt);

                /*
                 * Note that we ignore the result of setting the above
                 * breakpoint since it may fail.  When it does, this is
                 * not so much an error, but a forewarning that we may
                 * be receiving a prefetch abort shortly.
                 *
                 * If we don't set this breakpoint here, then we can
                 * loose control of the thread during single stepping.
                 */
                if (!alt || predicate(insn) != PREDICATE_ALWAYS)
                        add_breakpoint(dbg, pc + 4);
        }
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
void jelie_cancel_bpt()
{
        int i, nsaved = dbg->nsaved;

        dbg->nsaved = 0;

        if (nsaved > 2) {
                printf("jelie_cancel_bpt: bogus nsaved: %d!\n", nsaved);
                nsaved = 2;
        }

        for (i = 0; i < nsaved; i++)
                clear_breakpoint(dbg->bp+i);
}

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