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SubjectRe: [PATCH 2/4] x86/bus_lock: Handle warn and fatal in #DB for bus lock
On Sun, Nov 08, 2020 at 04:29:16AM +0000, Fenghua Yu wrote:
> split_lock_detect=
> #AC for split lock #DB for bus lock
>
> off Do nothing Do nothing
>
> warn Kernel OOPs Warn once per task and
> Warn once per task and and continues to run.
> disable future checking When both features are
> supported, warn in #DB
>
> fatal Kernel OOPs Send SIGBUS to user
> Send SIGBUS to user
> When both features are
> supported, fatal in #AC.

> +void handle_bus_lock(struct pt_regs *regs)
> +{
> + if (!bld)
> + return;
> +
> + pr_warn_ratelimited("#DB: %s/%d took a bus_lock trap at address: 0x%lx\n",
> + current->comm, current->pid, regs->ip);
> +}

So the Changelog above, and the state_show() below, seem to suggest
there should be SIGBUS code in #DB, but I'm having trouble spotting it.

> +static void sld_state_show(void)
> +{
> + if (!bld && !sld)
> + return;
> +
> + switch (sld_state) {
> + case sld_off:
> + pr_info("disabled\n");
> + break;
> +
> + case sld_warn:
> + if (bld)
> + pr_info("#DB: warning about user-space bus_locks\n");
> + else
> + pr_info("#AC: crashing the kernel about kernel split_locks and warning about user-space split_locks\n");
> + break;
> +
> + case sld_fatal:
> + if (sld)
> + pr_info("#AC: crashing the kernel on kernel split_locks and sending SIGBUS on user-space split_locks\n");
> + else
> + pr_info("#DB: sending SIGBUS on user-space bus_locks\n");
> + break;
> + }
> +}

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