On 11/20, Oleg Nesterov wrote:
>
> On 11/19, Steven Rostedt wrote:
> >
> > Is this really what we want?
>
> I am not sure, that is why I am asking.
Yes.
And,
> Well yes, with the new implementation __vsyscall_page simply does
> syscall, so I guess (say) strace will "just work". But, afaics, only
> if vsyscall_mode == NATIVE.
>
> So perhaps bp in vsyscall_page still makes sense...
Or. Perhaps we can define TRAP_VSYSCALL and change emulate_vsyscall() to do
if (current->ptrace && test_thread_flag(TIF_SYSCALL_TRACE))
send_sigtrap(TRAP_VSYSCALL, ...);
if it returns true?
This way the debugger doesn't need to play with the debug registers,
it can use ptrace(PTRACE_SYSCALL). The tracee will report SIGTRAP after
vsyscall, debugger can detect this case looking at info->si_code.
Yes, the tracee won't report _before_ it calls the function, but perhaps
this is enough? Amnon?
Oleg.
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