linux-kernel - [PATCH 4.12 143/196] MIPS: Send SIGILL for linked branches in `__compute_return_epc_for

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Date:   Tue, 25 Jul 2017 12:22:22 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Maciej W. Rozycki" <macro@...tec.com>,
        James Hogan <james.hogan@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.12 143/196] MIPS: Send SIGILL for linked branches in `__compute_return_epc_for_insn

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maciej W. Rozycki <macro@...tec.com>

commit fef40be6da856afead4177aaa9d869a66fb3381f upstream.

Fix commit 319824eabc3f ("MIPS: kernel: branch: Do not emulate the
branch likelies on MIPS R6") and also send SIGILL rather than returning
-SIGILL for BLTZAL, BLTZALL, BGEZAL and BGEZALL instruction encodings no
longer supported in R6, except where emulated.  Returning -SIGILL is
never correct as the API defines this function's result upon error to be
-EFAULT and a signal actually issued.

Fixes: 319824eabc3f ("MIPS: kernel: branch: Do not emulate the branch likelies on MIPS R6")
Signed-off-by: Maciej W. Rozycki <macro@...tec.com>
Cc: James Hogan <james.hogan@...tec.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16398/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/branch.c |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -473,10 +473,8 @@ int __compute_return_epc_for_insn(struct
 		case bltzal_op:
 		case bltzall_op:
 			if (NO_R6EMU && (insn.i_format.rs ||
-			    insn.i_format.rt == bltzall_op)) {
-				ret = -SIGILL;
-				break;
-			}
+			    insn.i_format.rt == bltzall_op))
+				goto sigill_r2r6;
 			regs->regs[31] = epc + 8;
 			/*
 			 * OK we are here either because we hit a NAL
@@ -507,10 +505,8 @@ int __compute_return_epc_for_insn(struct
 		case bgezal_op:
 		case bgezall_op:
 			if (NO_R6EMU && (insn.i_format.rs ||
-			    insn.i_format.rt == bgezall_op)) {
-				ret = -SIGILL;
-				break;
-			}
+			    insn.i_format.rt == bgezall_op))
+				goto sigill_r2r6;
 			regs->regs[31] = epc + 8;
 			/*
 			 * OK we are here either because we hit a BAL