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Commit e9d92d22 authored by Markos Chandras's avatar Markos Chandras Committed by Ralf Baechle
Browse files

MIPS: Fix branch emulation for BLTC and BGEC instructions 



Commits f1b44067 ("MIPS: Emulate the
new MIPS R6 B{L,G}T{Z,}{AL,}C instructions") and commit
a8ff66f5 ("MIPS: Emulate the new MIPS
R6 B{L,G}E{Z,}{AL,}C instructions") added support for emulating various
branch compact instructions. However, it missed the case for those which
use the old BLEZL and BGTZL opcodes leading to random crashes when the R6
emulator is disabled. We fix this by ensuring that the 'rt' field is not
zero which is always true for these branch compact instructions.

Fixes: f1b44067 ("MIPS: Emulate the new MIPS R6 B{L,G}T{Z,}{AL,}C instructions")
Fixes: a8ff66f5 ("MIPS: Emulate the new MIPS R6 B{L,G}E{Z,}{AL,}C instructions")
Cc: <stable@vger.kernel.org> # 4.0+
Signed-off-by: default avatarMarkos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/10582/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 761b4493

arch/mips/kernel/branch.c

+2 −2
Original line number Diff line number Diff line
@@ -600,7 +600,7 @@ int __compute_return_epc_for_insn(struct pt_regs *regs, 
		break;



	case blezl_op: /* not really i_format */

		if (NO_R6EMU)

		if (!insn.i_format.rt && NO_R6EMU)

			goto sigill_r6;

	case blez_op:

		/*
@@ -635,7 +635,7 @@ int __compute_return_epc_for_insn(struct pt_regs *regs, 
		break;



	case bgtzl_op:

		if (NO_R6EMU)

		if (!insn.i_format.rt && NO_R6EMU)

			goto sigill_r6;

	case bgtz_op:

		/*

arch/mips/math-emu/cp1emu.c

+2 −2
Original line number Diff line number Diff line
@@ -551,7 +551,7 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, 
				dec_insn.next_pc_inc;

		return 1;

	case blezl_op:

		if (NO_R6EMU)

		if (!insn.i_format.rt && NO_R6EMU)

			break;

	case blez_op:
@@ -588,7 +588,7 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, 
				dec_insn.next_pc_inc;

		return 1;

	case bgtzl_op:

		if (NO_R6EMU)

		if (!insn.i_format.rt && NO_R6EMU)

			break;

	case bgtz_op:

		/*