[PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system call
takahiro.akashi at linaro.org
Tue Sep 2 01:47:29 PDT 2014
On 09/01/2014 08:47 PM, Russell King - ARM Linux wrote:
> On Wed, Aug 27, 2014 at 02:55:46PM +0900, AKASHI Takahiro wrote:
>> setting x0 to -ENOSYS is necessary because, otherwise, user-issued syscall(-1) will
>> return a bogus value when audit tracing is on.
>> Please note that, on arm,
>> not traced traced
>> ------ ------
>> syscall(-1) aborted OOPs(BUG_ON)
>> syscall(-3000) aborted aborted
>> syscall(1000) ENOSYS ENOSYS
> Two points here:
> 1. You've found a case which causes a BUG_ON(). Where is the bug report
> for this, so the problem can be investigated and resolved?
I think that I mentioned it could also happen on arm somewhere in a talk with Will,
but don't remember exactly when.
> 2. What do you mean by "aborted" ?
I mean that the process will receive SIGILL and get aborted.
A system call number, like -1 and -3000, won't be trapped by *switch* statement
in asm_syscall() and end up with being signaled.
> Please, if you find a problem with 32-bit ARM, report it. Don't hide it,
> because hiding it can be a security issue or in the case of BUG_ON(), it
> could be a denial of service issue.
> As you're part of Linaro, I would have thought you'd be more responsible
> in this regard - after all, Linaro is supposed to be about improving the
> ARM kernel... Maybe I got that wrong, and Linaro is actually about
> ensuring that the ARM kernel is stuffed full of broken features?
I thought my first priority was on arm64 (and then arm), but now that you and Will
seem to want to see the fix first on arm, okey, I will start with arm issue.
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