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A mirror of the official Linux kernel repository just in case
56809a28d4
... not PGD vmalloc() sets up the kernel page table (starting from @swapper_pg_dir). But when vmalloc area is accessed in context of a user task, say opening terminal in n_tty_open(), the user page tables need to be synced from kernel page tables so that TLB entry is created in "user context". The old code was doing this incorrectly, as it was updating the user pgd entry (first level itself) to point to kernel pud table (2nd level), effectively yanking away the entire user space translation with kernel one. The correct way to do this is to ONLY update a user space pgd/pud/pmd entry if it is not popluated already. This ensures that only the missing leaf pmd entry gets updated to point to relevant kernel pte table. From code change pov, we are chaging the pattern: p4d = p4d_offset(pgd, address); p4d_k = p4d_offset(pgd_k, address); if (!p4d_present(*p4d_k)) goto bad_area; set_p4d(p4d, *p4d_k); with p4d = p4d_offset(pgd, address); p4d_k = p4d_offset(pgd_k, address); if (p4d_none(*p4d_k)) goto bad_area; if (!p4d_present(*p4d)) set_p4d(p4d, *p4d_k); Signed-off-by: Vineet Gupta <vgupta@kernel.org> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.