[PATCH v2 4/9] arm64: factor insn read out of call_undef_hook()

Mark Rutland
2022-10-19T15:03:46Z

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>
---
arch/arm64/kernel/traps.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index ccd7d773e5cd..4d51afd010e1 100644
--- 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);