1 files changed, 141 insertions, 0 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
new file mode 100644
index 000000000000..e79123d1485c
--- /dev/null
+++ b/arch/powerpc/lib/sstep.c
@@ -0,0 +1,141 @@
+/*
+ * Single-step support.
+ *
+ * Copyright (C) 2004 Paul Mackerras <paulus@au.ibm.com>, IBM
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/kernel.h>
+#include <linux/ptrace.h>
+#include <asm/sstep.h>
+#include <asm/processor.h>
+
+extern char system_call_common[];
+
+/* Bits in SRR1 that are copied from MSR */
+#define MSR_MASK        0xffffffff87c0ffff
+
+/*
+ * Determine whether a conditional branch instruction would branch.
+ */
+static int branch_taken(unsigned int instr, struct pt_regs *regs)
+{
+        unsigned int bo = (instr >> 21) & 0x1f;
+        unsigned int bi;
+
+        if ((bo & 4) == 0) {
+                /* decrement counter */
+                --regs->ctr;
+                if (((bo >> 1) & 1) ^ (regs->ctr == 0))
+                        return 0;
+        }
+        if ((bo & 0x10) == 0) {
+                /* check bit from CR */
+                bi = (instr >> 16) & 0x1f;
+                if (((regs->ccr >> (31 - bi)) & 1) != ((bo >> 3) & 1))
+                        return 0;
+        }
+        return 1;
+}
+
+/*
+ * Emulate instructions that cause a transfer of control.
+ * Returns 1 if the step was emulated, 0 if not,
+ * or -1 if the instruction is one that should not be stepped,
+ * such as an rfid, or a mtmsrd that would clear MSR_RI.
+ */
+int emulate_step(struct pt_regs *regs, unsigned int instr)
+{
+        unsigned int opcode, rd;
+        unsigned long int imm;
+
+        opcode = instr >> 26;
+        switch (opcode) {
+        case 16:        /* bc */
+                imm = (signed short)(instr & 0xfffc);
+                if ((instr & 2) == 0)
+                        imm += regs->nip;
+                regs->nip += 4;
+                if ((regs->msr & MSR_SF) == 0)
+                        regs->nip &= 0xffffffffUL;
+                if (instr & 1)
+                        regs->link = regs->nip;
+                if (branch_taken(instr, regs))
+                        regs->nip = imm;
+                return 1;
+        case 17:        /* sc */
+                /*
+                 * N.B. this uses knowledge about how the syscall
+                 * entry code works.  If that is changed, this will
+                 * need to be changed also.
+                 */
+                regs->gpr[9] = regs->gpr[13];
+                regs->gpr[11] = regs->nip + 4;
+                regs->gpr[12] = regs->msr & MSR_MASK;
+                regs->gpr[13] = (unsigned long) get_paca();
+                regs->nip = (unsigned long) &system_call_common;
+                regs->msr = MSR_KERNEL;
+                return 1;
+        case 18:        /* b */
+                imm = instr & 0x03fffffc;
+                if (imm & 0x02000000)
+                        imm -= 0x04000000;
+                if ((instr & 2) == 0)
+                        imm += regs->nip;
+                if (instr & 1) {
+                        regs->link = regs->nip + 4;
+                        if ((regs->msr & MSR_SF) == 0)
+                                regs->link &= 0xffffffffUL;
+                }
+                if ((regs->msr & MSR_SF) == 0)
+                        imm &= 0xffffffffUL;
+                regs->nip = imm;
+                return 1;
+        case 19:
+                switch (instr & 0x7fe) {
+                case 0x20:      /* bclr */
+                case 0x420:     /* bcctr */
+                        imm = (instr & 0x400)? regs->ctr: regs->link;
+                        regs->nip += 4;
+                        if ((regs->msr & MSR_SF) == 0) {
+                                regs->nip &= 0xffffffffUL;
+                                imm &= 0xffffffffUL;
+                        }
+                        if (instr & 1)
+                                regs->link = regs->nip;
+                        if (branch_taken(instr, regs))
+                                regs->nip = imm;
+                        return 1;
+                case 0x24:      /* rfid, scary */
+                        return -1;
+                }
+        case 31:
+                rd = (instr >> 21) & 0x1f;
+                switch (instr & 0x7fe) {
+                case 0xa6:      /* mfmsr */
+                        regs->gpr[rd] = regs->msr & MSR_MASK;
+                        regs->nip += 4;
+                        if ((regs->msr & MSR_SF) == 0)
+                                regs->nip &= 0xffffffffUL;
+                        return 1;
+                case 0x164:     /* mtmsrd */
+                        /* only MSR_EE and MSR_RI get changed if bit 15 set */
+                        /* mtmsrd doesn't change MSR_HV and MSR_ME */
+                        imm = (instr & 0x10000)? 0x8002: 0xefffffffffffefffUL;
+                        imm = (regs->msr & MSR_MASK & ~imm)
+                                | (regs->gpr[rd] & imm);
+                        if ((imm & MSR_RI) == 0)
+                                /* can't step mtmsrd that would clear MSR_RI */
+                                return -1;
+                        regs->msr = imm;
+                        regs->nip += 4;
+                        if ((imm & MSR_SF) == 0)
+                                regs->nip &= 0xffffffffUL;
+                        return 1;
+                }
+        }
+        return 0;
+}