On Thu, Oct 30, 2014 at 07:10:39AM -0400, Steven Rostedt wrote:

On Thu, 30 Oct 2014 10:18:08 +0000
Russell King - ARM Linux [off-list ref] wrote:

quoted

On Thu, Oct 30, 2014 at 01:26:06AM -0700, Christoph Hellwig wrote:

quoted

On Wed, Oct 29, 2014 at 11:06:58PM +0100, Rabin Vincent wrote:

quoted

ARM has some private syscalls (for example, set_tls(2)) which lie
outside the range of NR_syscalls.  If any of these are called while
syscall tracing is being performed, out-of-bounds array access will
occur in the ftrace and perf sys_{enter,exit} handlers.

While this patch looks like good caution, having syscalls outside of
NR_syscalls seems like a receipe for a disaster.  Can you try to fix
that issue as ell, please?

No.  We've had them since the inception of Linux on ARM.  They predate
this tracing crap by more than a decade.  We're not changing them
because that would be a massive user API breakage.

Since syscall tracing is only broken on ARM, then the fix needs to be
ARM specific, and not remove the check for all other architectures that
have a sane NR_syscalls variable.

This issue came up before.

We have always had syscall number range of 0x900000 or so.  The tracing
design does not expect that.  Therefore, the tracing design did not take
account of ARM when it was created.  Therefore, it's up to the tracing
people to decide how to properly fit their ill-designed subsystem into
one of the popular and well-established kernel architectures - or at
least suggest a way to work around this issue.

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