Re: [PATCH] signal/nds32: More information in do_revinsn
From: Vincent Chen
Date: Wed Apr 25 2018 - 23:03:04 EST
2018-04-26 0:13 GMT+08:00 Eric W. Biederman <ebiederm@xxxxxxxxxxxx>:
> While reviewing f6ed1ecad56f ("signal/nds32: Use force_sig(SIGILL) in do_revisn")
> Vincent Chen asked if it was possible to provide more information in do_revinsn
> with force_sig_fault.
> That seems reasonable and the appropirate si_code appears to be
> ILL_ILLOPC (illegal opcode) as the printk indicates this code path
> is triggered when a reserved instruction is exectured.
I think error code is set as ILL_ILLOPC is a good choice for normal
but it seems a little bit inappropriate for nds32. For nds32 reserved
exception, It is possibly
triggered by illegal opcode, operand and immediate. Unfortunately,
do_revisn() can not
identify the actual reason now. Therefore, I chose ILLTRAP to avoid
confusing user when
the reserved exception is cauesd by wrong immediate or operand.
> So update do_revinsn to use force_sig_fault(SIGILL, ILL_ILLOPC, ...).
> Giving userspace a much better experience when soemone attempts
> to execute a reserved instruction.
> Cc: Greentime Hu <green.hu@xxxxxxxxx>
> Cc: Vincent Chen <deanbo422@xxxxxxxxx>
> Suggested-by: Vincent Chen <deanbo422@xxxxxxxxx>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> Vincent I have updated this from your suggestion to use
> ILL_ILLOPC as that appears the more appropriate si_code.
> Normally I expect you could just update your nds32 tree and
> make this kind of change but since I am touching this code anyway I will
> be happy to take this change along with the others.
> Does this look good to you?
It is fine to commit this change along with the others.
> arch/nds32/kernel/traps.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> diff --git a/arch/nds32/kernel/traps.c b/arch/nds32/kernel/traps.c
> index a6205fd4db52..5c2f61835ab9 100644
> --- a/arch/nds32/kernel/traps.c
> +++ b/arch/nds32/kernel/traps.c
> @@ -349,7 +349,8 @@ void do_revinsn(struct pt_regs *regs)
> if (!user_mode(regs))
> - force_sig(SIGILL, current);
> + force_sig_fault(SIGILL, ILL_ILLOPC,
> + (void __user *)instruction_pointer(regs), current);
> #ifdef CONFIG_ALIGNMENT_TRAP