[PATCH] lib/sstep: Fix incorrect return from analyze_instr()

[Ananth N Mavinakayanahalli <ananth@linux.ibm.com>]

We currently just percolate the return value from analyze_instr()
to the caller of emulate_step(), especially if it is a -1.

For one particular case (opcode = 4) for instructions that
aren't currently emulated, we are returning 'should not be
single-stepped' while we should have returned 0 which says
'did not emulate, may have to single-step'.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@linux.ibm.com>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/lib/sstep.c |   49 +++++++++++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 5a425a4a1d88..a3a0373843cd 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -1445,34 +1445,39 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
 
 #ifdef __powerpc64__
 	case 4:
-		if (!cpu_has_feature(CPU_FTR_ARCH_300))
-			return -1;
-
-		switch (word & 0x3f) {
-		case 48:	/* maddhd */
-			asm volatile(PPC_MADDHD(%0, %1, %2, %3) :
-				     "=r" (op->val) : "r" (regs->gpr[ra]),
-				     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
-			goto compute_done;
+		/*
+		 * There are very many instructions with this primary opcode
+		 * introduced in the ISA as early as v2.03. However, the ones
+		 * we currently emulate were all introduced with ISA 3.0
+		 */
+		if (cpu_has_feature(CPU_FTR_ARCH_300)) {
+			switch (word & 0x3f) {
+			case 48:	/* maddhd */
+				asm volatile(PPC_MADDHD(%0, %1, %2, %3) :
+					     "=r" (op->val) : "r" (regs->gpr[ra]),
+					     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
+				goto compute_done;
 
-		case 49:	/* maddhdu */
-			asm volatile(PPC_MADDHDU(%0, %1, %2, %3) :
-				     "=r" (op->val) : "r" (regs->gpr[ra]),
-				     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
-			goto compute_done;
+			case 49:	/* maddhdu */
+				asm volatile(PPC_MADDHDU(%0, %1, %2, %3) :
+					     "=r" (op->val) : "r" (regs->gpr[ra]),
+					     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
+				goto compute_done;
 
-		case 51:	/* maddld */
-			asm volatile(PPC_MADDLD(%0, %1, %2, %3) :
-				     "=r" (op->val) : "r" (regs->gpr[ra]),
-				     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
-			goto compute_done;
+			case 51:	/* maddld */
+				asm volatile(PPC_MADDLD(%0, %1, %2, %3) :
+					     "=r" (op->val) : "r" (regs->gpr[ra]),
+					     "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
+				goto compute_done;
+			}
 		}
 
 		/*
-		 * There are other instructions from ISA 3.0 with the same
-		 * primary opcode which do not have emulation support yet.
+		 * Rest of the instructions with this primary opcode do not
+		 * have emulation support yet.
 		 */
-		return -1;
+		op->type = UNKNOWN;
+		return 0;
 #endif
 
 	case 7:		/* mulli */