From 718aae916fa6619c57c348beaedd675835cf1aa1 Mon Sep 17 00:00:00 2001

From: Ananth N Mavinakayanahalli <ananth@linux.ibm.com>

Date: Mon, 25 Jan 2021 18:36:43 +0530

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

References: bsc#1156395

Patch-mainline: v5.12-rc1

Git-commit: 718aae916fa6619c57c348beaedd675835cf1aa1

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'.

Fixes: 930d6288a26787 ("powerpc: sstep: Add support for maddhd, maddhdu, maddld instructions")

Signed-off-by: Ananth N Mavinakayanahalli <ananth@linux.ibm.com>

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>

Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Link: https://lore.kernel.org/r/161157999039.64773.14950289716779364766.stgit@thinktux.local

Acked-by: Michal Suchanek <msuchanek@suse.de>

---

 arch/powerpc/lib/sstep.c | 7 ++++++-

 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c

index f859cbbb6375..e96cff845ef7 100644

--- a/arch/powerpc/lib/sstep.c

+++ b/arch/powerpc/lib/sstep.c

@@ -1445,6 +1445,11 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,

 #ifdef __powerpc64__

 	case 4:

+		/*

+		 * 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))

 			goto unknown_opcode;

@@ -1472,7 +1477,7 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,

 		 * There are other instructions from ISA 3.0 with the same

 		 * primary opcode which do not have emulation support yet.

 		 */

-		return -1;

+		goto unknown_opcode;

 #endif

 	case 7:		/* mulli */

-- 

2.26.2