340a982825
Actually in no-MMU SoCs(i.e. i.MXRT) ZERO_PAGE(vaddr) expands to
```
virt_to_page(0)
```
that in order expands to:
```
pfn_to_page(virt_to_pfn(0))
```
and then virt_to_pfn(0) to:
```
((((unsigned long)(0) - PAGE_OFFSET) >> PAGE_SHIFT) +
PHYS_PFN_OFFSET)
```
where PAGE_OFFSET and PHYS_PFN_OFFSET are the DRAM offset(0x80000000) and
PAGE_SHIFT is 12. This way we obtain 16MB(0x01000000) summed to the base of
DRAM(0x80000000).
When ZERO_PAGE(0) is then used, for example in bio_add_page(), the page
gets an address that is out of DRAM bounds.
So instead of using fake virtual page 0 let's allocate a dedicated
zero_page during paging_init() and assign it to a global 'struct page *
empty_zero_page' the same way mmu.c does and it's the same approach used
in m68k with commit
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.