Commit 3330a05c authored Jun 16, 2017 by Maciej W. Rozycki Committed by Greg Kroah-Hartman Jul 27, 2017

MIPS: Send SIGILL for R6 branches in `__compute_return_epc_for_insn'



commit a60b1a5bf88a250f1a77977c0224e502c901c77b upstream.

Fix:

* commit 8467ca01 ("MIPS: Emulate the new MIPS R6 branch compact
(BC) instruction"),

* commit 84fef630 ("MIPS: Emulate the new MIPS R6 BALC
instruction"),

* commit 69b9a2fd ("MIPS: Emulate the new MIPS R6 BEQZC and JIC
instructions"),

* commit 28d6f93d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC
instructions"),

* commit c893ce38 ("MIPS: Emulate the new MIPS R6 BOVC, BEQC and
BEQZALC instructions")

and send SIGILL rather than returning -SIGILL for R6 branch and jump
instructions.  Returning -SIGILL is never correct as the API defines
this function's result upon error to be -EFAULT and a signal actually
issued.

Fixes: 8467ca01 ("MIPS: Emulate the new MIPS R6 branch compact (BC) instruction")
Fixes: 84fef630 ("MIPS: Emulate the new MIPS R6 BALC instruction")
Fixes: 69b9a2fd ("MIPS: Emulate the new MIPS R6 BEQZC and JIC instructions")
Fixes: 28d6f93d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions")
Fixes: c893ce38 ("MIPS: Emulate the new MIPS R6 BOVC, BEQC and BEQZALC instructions")
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16399/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d4bd6a1d

arch/mips/kernel/branch.c

+15 −20

Original line number	Diff line number	Diff line
		@@ -771,35 +771,27 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
		#else
		case bc6_op:
		/* Only valid for MIPS R6 */
		if (!cpu_has_mips_r6) {
		ret = -SIGILL;
		break;
		}
		if (!cpu_has_mips_r6)
		goto sigill_r6;
		regs->cp0_epc += 8;
		break;
		case balc6_op:
		if (!cpu_has_mips_r6) {
		ret = -SIGILL;
		break;
		}
		if (!cpu_has_mips_r6)
		goto sigill_r6;
		/* Compact branch: BALC */
		regs->regs[31] = epc + 4;
		epc += 4 + (insn.i_format.simmediate << 2);
		regs->cp0_epc = epc;
		break;
		case pop66_op:
		if (!cpu_has_mips_r6) {
		ret = -SIGILL;
		break;
		}
		if (!cpu_has_mips_r6)
		goto sigill_r6;
		/* Compact branch: BEQZC \|\| JIC */
		regs->cp0_epc += 8;
		break;
		case pop76_op:
		if (!cpu_has_mips_r6) {
		ret = -SIGILL;
		break;
		}
		if (!cpu_has_mips_r6)
		goto sigill_r6;
		/* Compact branch: BNEZC \|\| JIALC */
		if (!insn.i_format.rs) {
		/* JIALC: set $31/ra */
		@@ -811,10 +803,8 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
		case pop10_op:
		case pop30_op:
		/* Only valid for MIPS R6 */
		if (!cpu_has_mips_r6) {
		ret = -SIGILL;
		break;
		}
		if (!cpu_has_mips_r6)
		goto sigill_r6;
		/*
		* Compact branches:
		* bovc, beqc, beqzalc, bnvc, bnec, bnezlac
		@@ -837,6 +827,11 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
		current->comm);
		force_sig(SIGILL, current);
		return -EFAULT;
		sigill_r6:
		pr_info("%s: R6 branch but no MIPSr6 ISA support - sending SIGILL.\n",
		current->comm);
		force_sig(SIGILL, current);
		return -EFAULT;
		}
		EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);