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SubjectRe: [PATCH 3/5] arm64: Handle TRAP_HWBRKPT for user mode as well
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On 09/06/2016 12:11 PM, Catalin Marinas wrote:
> On Tue, Aug 02, 2016 at 11:00:07AM +0530, Pratyush Anand wrote:
>> --- a/arch/arm64/kernel/debug-monitors.c
>> +++ b/arch/arm64/kernel/debug-monitors.c
>> @@ -246,6 +246,8 @@ static void send_user_sigtrap(int si_code)
>> static int single_step_handler(unsigned long addr, unsigned int esr,
>> struct pt_regs *regs)
>> {
>> + bool handler_found = false;
>> +
>> /*
>> * If we are stepping a pending breakpoint, call the hw_breakpoint
>> * handler first.
>> @@ -253,7 +255,14 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
>> if (!reinstall_suspended_bps(regs))
>> return 0;
>>
>> - if (user_mode(regs)) {
>> +#ifdef CONFIG_KPROBES
>> + if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
>> + handler_found = true;
>> +#endif
>> + if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
>> + handler_found = true;
>> +
>> + if (!handler_found && user_mode(regs)) {
>> send_user_sigtrap(TRAP_HWBKPT);
>
> Could we register kprobe_single_step_handler() via register_set_hook()
> and only invoke call_step_hook() above?
>

I seem to recall a criticism of doing that in a much earlier kprobes64
patch of mine. The concern was that it would cause unnecessarily more
kernel functions to be kprobes-blacklisted. Hence the hardcoded check
and call.

-dl

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