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The URLs of the form `help://man/<section>/<page>` link to another help page inside the help application. All previous relative page links are replaced by this new form. This doesn't change any behavior but it looks much nicer :^) Note that man doesn't handle these new links, but the previous relative links didn't work either.
31 lines
904 B
Markdown
31 lines
904 B
Markdown
## Name
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mem - physical system memory
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## Description
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`/dev/mem` is a character device file that is used by other programs to examine
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the physical memory.
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Trying to [`mmap`(2)](help://man/2/mmap) a physical range results either with success,
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or with an error. When invoking [`mmap`(2)](help://man/2/mmap) on bad memory range,
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the kernel will write a message about it to the kernel log.
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By default, the kernel limits the areas which can be accessed. The allowed areas
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are the reserved ranges in physical memory, essentially limiting the access to
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ROMs and memory-mapped PCI regions on x86.
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To create it manually:
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```sh
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mknod /dev/mem c 1 1
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chmod 660 /dev/mem
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```
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## Returned error values after [`mmap`(2)](help://man/2/mmap)
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* `EINVAL`: An access violation was detected.
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* `ENOMEM`: The requested range would wrap around, creating an access violation.
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## See also
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* [`mmap`(2)](help://man/2/mmap)
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