arm64: factor insn read out of call_undef_hook()

Subsequent patches will rework EL0 UNDEF handling, removing the need for
struct undef_hook and call_undef_hook. In preparation for those changes,
this patch factors the logic for reading user instructions out of
call_undef_hook() and into a new user_insn_read() helper, matching the
style of the existing aarch64_insn_read() helper used for reading kernel
instructions.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20221019144123.612388-5-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index ccd7d773e5cdcdef22411aa56b5134aae06bf0f1..4d51afd010e1ca5ecf57c18cda6aae2000531f0b 100644 (file)
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -394,25 +394,22 @@ void unregister_undef_hook(struct undef_hook *hook)
        raw_spin_unlock_irqrestore(&undef_lock, flags);
 }
 
-static int call_undef_hook(struct pt_regs *regs)
+static int user_insn_read(struct pt_regs *regs, u32 *insnp)
 {
-       struct undef_hook *hook;
-       unsigned long flags;
        u32 instr;
-       int (*fn)(struct pt_regs *regs, u32 instr) = NULL;
        unsigned long pc = instruction_pointer(regs);
 
        if (compat_thumb_mode(regs)) {
                /* 16-bit Thumb instruction */
                __le16 instr_le;
                if (get_user(instr_le, (__le16 __user *)pc))
-                       goto exit;
+                       return -EFAULT;
                instr = le16_to_cpu(instr_le);
                if (aarch32_insn_is_wide(instr)) {
                        u32 instr2;
 
                        if (get_user(instr_le, (__le16 __user *)(pc + 2)))
-                               goto exit;
+                               return -EFAULT;
                        instr2 = le16_to_cpu(instr_le);
                        instr = (instr << 16) | instr2;
                }
@@ -420,10 +417,20 @@ static int call_undef_hook(struct pt_regs *regs)
                /* 32-bit ARM instruction */
                __le32 instr_le;
                if (get_user(instr_le, (__le32 __user *)pc))
-                       goto exit;
+                       return -EFAULT;
                instr = le32_to_cpu(instr_le);
        }
 
+       *insnp = instr;
+       return 0;
+}
+
+static int call_undef_hook(struct pt_regs *regs, u32 instr)
+{
+       struct undef_hook *hook;
+       unsigned long flags;
+       int (*fn)(struct pt_regs *regs, u32 instr) = NULL;
+
        raw_spin_lock_irqsave(&undef_lock, flags);
        list_for_each_entry(hook, &undef_hook, node)
                if ((instr & hook->instr_mask) == hook->instr_val &&
@@ -431,7 +438,7 @@ static int call_undef_hook(struct pt_regs *regs)
                        fn = hook->fn;
 
        raw_spin_unlock_irqrestore(&undef_lock, flags);
-exit:
+
        return fn ? fn(regs, instr) : 1;
 }
 
@@ -483,13 +490,19 @@ void arm64_notify_segfault(unsigned long addr)
 
 void do_el0_undef(struct pt_regs *regs, unsigned long esr)
 {
+       u32 insn;
+
        /* check for AArch32 breakpoint instructions */
        if (!aarch32_break_handler(regs))
                return;
 
-       if (call_undef_hook(regs) == 0)
+       if (user_insn_read(regs, &insn))
+               goto out_err;
+
+       if (call_undef_hook(regs, insn) == 0)
                return;
 
+out_err:
        force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
 }