From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Sat, 16 Apr 2005 15:20:36 -0700
Subject: Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
---
 arch/ppc64/lib/sstep.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 arch/ppc64/lib/sstep.c

(limited to 'arch/ppc64/lib/sstep.c')

diff --git a/arch/ppc64/lib/sstep.c b/arch/ppc64/lib/sstep.c
new file mode 100644
index 000000000000..e79123d1485c
--- /dev/null
+++ b/arch/ppc64/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;
+}
-- 
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