[BUG] Problems with reading the ZERO_PAGE via ptrace

From: Nick Rasmussen (nick@jive.org)
Date: Tue May 30 2000 - 14:07:56 EST


In 2.4.0-test1, (and other 2.3 kernels) the zero page is flagged as being
reserved. Unfortunately, if you are using ptrace to read out of a part of
an inferior process' address space that is mapped to the ZERO_PAGE, ptrace
will return with an IO error, as it is complying with the definition of the
reserved bit:

[snip]
 * PG_reserved is set for a page which must never be accessed (which
 * may not even be present).
[snip]

So my question is: Should the ZERO_PAGE actually be marked as reserved?
If so, the attached patch (or something similar) should probably be applied
to fix the behavior of ptrace.

-nick



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