What is a WP?

  • Thread starter Thread starter Mark Hobley
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Mark Hobley

I am looking at some source code written for the Linux kernel. There is
a reference X86_WP_WORKS_OK and some related comments about whether or
not the processor has a working WP. I am just wondering, what the hell that
means. What is a WP? I have never heard of this.

Mark.
 
I am looking at some source code written for the Linux kernel. There is
a reference X86_WP_WORKS_OK and some related comments about whether or
not the processor has a working WP. I am just wondering, what the hell that
means. What is a WP? I have never heard of this.
Click to expand...

Write Protection.

WP is used to implement Copy On Write. When sharing a page between
several processes, the page is marked read-only. Attempts to write
into such a page trap to an error handler in the OS which then makes
a private - writable - copy of the page.

The original 386 honored WP only in user mode, not at level 0. This
requires a software work around.
 
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