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SubjectRe: [PATCH] arm64: setup return path for el1_undef
On Tue, Dec 23, 2014 at 03:15:10PM +0000, Min-Hua Chen wrote:
> Setup return path for el1_undef since el1_undef may
> be handled by handlers.

Did you find a real issue or it was just code inspection.

> asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
> {
> siginfo_t info;
> void __user *pc = (void __user *)instruction_pointer(regs);
>
> /* check for AArch32 breakpoint instructions */
> if (!aarch32_break_handler(regs))
> return;
>
> if (call_undef_hook(regs) == 0)
> return;
>
> ...
> }
> Signed-off-by: Min-Hua Chen <orca.chen@gmail.com>
> ---
> arch/arm64/kernel/entry.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index fd4fa37..86ebec5 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -313,7 +313,8 @@ el1_undef:
> */
> enable_dbg
> mov x0, sp
> - b do_undefinstr
> + bl do_undefinstr
> + kernel_exit 1
> el1_dbg:
> /*
> * Debug exception handling

I don't think this is needed. The code is pretty convoluted but for an
EL1 undefined exception we should never return from do_undefinstr(). The
call_undef_hook() function returns 1 if !user_mode(regs) and this should
cause a kernel panic. Basically we do not allow any kind of undefined
instructions in the arm64 kernel.

--
Catalin


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