linux-kernel - Re: [PATCH 4/4] riscv: remove the switch statement in do_trap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190927224711.GI4700@infradead.org>
Date:   Fri, 27 Sep 2019 15:47:11 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Vincent Chen <vincent.chen@...ive.com>
Cc:     linux-riscv@...ts.infradead.org, palmer@...ive.com,
        linux-kernel@...r.kernel.org, aou@...s.berkeley.edu,
        paul.walmsley@...ive.com
Subject: Re: [PATCH 4/4] riscv: remove the switch statement in do_trap_break()

On Mon, Sep 23, 2019 at 08:45:17AM +0800, Vincent Chen wrote:
> To make the code more straightforward, replacing the switch statement
> with if statement.
> 
> Suggested-by: Paul Walmsley <paul.walmsley@...ive.com>
> Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
> ---
>  arch/riscv/kernel/traps.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index dd13bc90aeb6..1ac75f7d0bff 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -124,23 +124,24 @@ static inline unsigned long get_break_insn_length(unsigned long pc)
>  
>  asmlinkage void do_trap_break(struct pt_regs *regs)
>  {
> +	if (user_mode(regs)) {
> +		force_sig_fault(SIGTRAP, TRAP_BRKPT,
> +				(void __user *)(regs->sepc));
> +		return;
> +	}
> +#ifdef CONFIG_GENERIC_BUG
> +	{
>  		enum bug_trap_type type;
>  
>  		type = report_bug(regs->sepc, regs);
> +		if (type == BUG_TRAP_TYPE_WARN) {
>  			regs->sepc += get_break_insn_length(regs->sepc);
>  			return;
>  		}
> +#endif /* CONFIG_GENERIC_BUG */
> +
> +	die(regs, "Kernel BUG");

I like where this is going, but I think this can be improved further
given that fact that report_bug has a nice stub for the
!CONFIG_GENERIC_BUG case.

How about:

	if (user_mode(regs))
		force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->sepc);
	else if (report_bug(regs->sepc, regs) == BUG_TRAP_TYPE_WARN)
		regs->sepc += get_break_insn_length(regs->sepc);
	else
		die(regs, "Kernel BUG");