From 47c25036b60f27b86ab44b66a8861bcf81cde39b Mon Sep 17 00:00:00 2001 From: Archer Yan Date: Fri, 8 Mar 2019 03:29:19 +0000 Subject: [PATCH] MIPS: Fix kernel crash for R6 in jump label branch function Insert Branch instruction instead of NOP to make sure assembler don't patch code in forbidden slot. In jump label function, it might be possible to patch Control Transfer Instructions(CTIs) into forbidden slot, which will generate Reserved Instruction exception in MIPS release 6. Signed-off-by: Archer Yan Reviewed-by: Paul Burton [paul.burton@mips.com: - Add MIPS prefix to subject. - Mark for stable from v4.0, which introduced r6 support, onwards.] Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org Cc: stable@vger.kernel.org # v4.0+ --- arch/mips/include/asm/jump_label.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h index e77672539e8e..e4456e450f94 100644 --- a/arch/mips/include/asm/jump_label.h +++ b/arch/mips/include/asm/jump_label.h @@ -21,15 +21,15 @@ #endif #ifdef CONFIG_CPU_MICROMIPS -#define NOP_INSN "nop32" +#define B_INSN "b32" #else -#define NOP_INSN "nop" +#define B_INSN "b" #endif static __always_inline bool arch_static_branch(struct static_key *key, bool branch) { - asm_volatile_goto("1:\t" NOP_INSN "\n\t" - "nop\n\t" + asm_volatile_goto("1:\t" B_INSN " 2f\n\t" + "2:\tnop\n\t" ".pushsection __jump_table, \"aw\"\n\t" WORD_INSN " 1b, %l[l_yes], %0\n\t" ".popsection\n\t"