[PATCH AUTOSEL 4.19 059/146] arm64: entry: Allow handling of undefined instructions from EL1

[Sasha Levin]

From: Will Deacon <will.dea...@arm.com>

[ Upstream commit 0bf0f444b2c49241b2b39aa3cf210d7c95ef6c34 ]

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 <will.dea...@arm.com>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 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)
-- 
2.17.1