nullptr(1)

nullptr -- per-user NULL pointer reference checking

Synopsis

   nullptr [enable | disable]

Description

The nullptr command supports three different behaviors when applications dereference through a NULL pointer. To support existing applications the default behavior as delivered is to enable null-pointer dereferences.

When null-pointer dereferences are enabled, any user program attempt to read memory in the first page (addresses 0-4095) will successfully return zero. When disabled, these memory reads behave like any other bad memory reference and cause a SIGSEGV signal to be sent to the referencing lightweight process. Memory writes to page 0 always generate SIGSEGV.

The default behavior can be changed by changing the NULLPTR tunable parameter.

The nullptr command can be used to override the default behavior for a particular user, based on the user ID of the invoking process.

The nullptr command can be called with the following arguments:

enable: With this argument, nullptr enables null-pointer references for the current user.
disable: With this argument, nullptr disables null-pointer references for the current user.

With no arguments, nullptr displays the behavior in effect for the current user.

References

sysi86(2)