From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Thu, 30 Aug 2018 17:16:04 +0100 Subject: [PATCH 4/7] arm64: entry: Allow handling of undefined instructions from EL1 In-Reply-To: <1535645767-9901-1-git-send-email-will.deacon@arm.com> References: <1535645767-9901-1-git-send-email-will.deacon@arm.com> Message-ID: <1535645767-9901-5-git-send-email-will.deacon@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Rather than panic() when taking an undefined instruction exception from EL1, allow a hook to be registered in case we want to emulate the instruction, like we will for the SSBS PSTATE manipulation instructions. Signed-off-by: Will Deacon --- arch/arm64/kernel/entry.S | 2 +- arch/arm64/kernel/traps.c | 11 +++++++---- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 09dbea221a27..8556876c9109 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -589,7 +589,7 @@ el1_undef: inherit_daif pstate=x23, tmp=x2 mov x0, sp bl do_undefinstr - ASM_BUG() + kernel_exit 1 el1_dbg: /* * Debug exception handling diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 039e9ff379cc..b9da093e0341 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -310,10 +310,12 @@ static int call_undef_hook(struct pt_regs *regs) int (*fn)(struct pt_regs *regs, u32 instr) = NULL; void __user *pc = (void __user *)instruction_pointer(regs); - if (!user_mode(regs)) - return 1; - - if (compat_thumb_mode(regs)) { + if (!user_mode(regs)) { + __le32 instr_le; + if (probe_kernel_address((__force __le32 *)pc, instr_le)) + goto exit; + instr = le32_to_cpu(instr_le); + } else if (compat_thumb_mode(regs)) { /* 16-bit Thumb instruction */ __le16 instr_le; if (get_user(instr_le, (__le16 __user *)pc)) @@ -407,6 +409,7 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs) return; force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc); + BUG_ON(!user_mode(regs)); } void cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused) -- 2.1.4