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SubjectRe: [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@sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen@sifive.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");

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