powerpc: Make single-stepping emulation (mostly) usable on 32-bit

The sc instruction emulation can't be done the same way on 32-bit
as 64-bit yet, but this should work OK.

Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 34 insertions, 0 deletions

diff --git a/include/asm-powerpc/reg.h b/include/asm-powerpc/reg.h
index 68058d72d8da..bfb45a4523d3 100644
--- a/include/asm-powerpc/reg.h
+++ b/include/asm-powerpc/reg.h
@@ -51,9 +51,17 @@
 #define __MASK(X)       (1UL<<(X))
 #endif
 
+#ifdef CONFIG_PPC64
 #define MSR_SF          __MASK(MSR_SF_LG)       /* Enable 64 bit mode */
 #define MSR_ISF         __MASK(MSR_ISF_LG)      /* Interrupt 64b mode valid on 630 */
 #define MSR_HV          __MASK(MSR_HV_LG)       /* Hypervisor state */
+#else
+/* so tests for these bits fail on 32-bit */
+#define MSR_SF          0
+#define MSR_ISF         0
+#define MSR_HV          0
+#endif
+
 #define MSR_VEC         __MASK(MSR_VEC_LG)      /* Enable AltiVec */
 #define MSR_POW         __MASK(MSR_POW_LG)      /* Enable Power Management */
 #define MSR_WE          __MASK(MSR_WE_LG)       /* Wait State Enable */
diff --git a/include/asm-powerpc/sstep.h b/include/asm-powerpc/sstep.h
new file mode 100644
index 000000000000..630a9889c07c
--- /dev/null
+++ b/include/asm-powerpc/sstep.h
@@ -0,0 +1,26 @@
+/*
+ * 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.
+ */
+
+struct pt_regs;
+
+/*
+ * We don't allow single-stepping an mtmsrd that would clear
+ * MSR_RI, since that would make the exception unrecoverable.
+ * Since we need to single-step to proceed from a breakpoint,
+ * we don't allow putting a breakpoint on an mtmsrd instruction.
+ * Similarly we don't allow breakpoints on rfid instructions.
+ * These macros tell us if an instruction is a mtmsrd or rfid.
+ * Note that IS_MTMSRD returns true for both an mtmsr (32-bit)
+ * and an mtmsrd (64-bit).
+ */
+#define IS_MTMSRD(instr)        (((instr) & 0xfc0007be) == 0x7c000124)
+#define IS_RFID(instr)          (((instr) & 0xfc0007fe) == 0x4c000024)
+
+/* Emulate instructions that cause a transfer of control. */
+extern int emulate_step(struct pt_regs *regs, unsigned int instr);