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If PGDIR_SIZE is too large for cpu_vabits, KASAN_SHADOW_END will overflow UINTPTR_MAX because KASAN_SHADOW_START/KASAN_SHADOW_END are aligned up by PGDIR_SIZE. And then the overflowed KASAN_SHADOW_END looks like a user space address. For example, PGDIR_SIZE of CONFIG_4KB_4LEVEL is 2^39, which is too large for Loongson-2K series whose cpu_vabits = 39. Since CONFIG_4KB_4LEVEL is completely legal for CPUs with cpu_vabits <= 39, we just disable KASAN via early return in kasan_init(). Otherwise we get a boot failure. Moreover, we change KASAN_SHADOW_END from the first address after KASAN shadow area to the last address in KASAN shadow area, in order to avoid the end address exactly overflow to 0 (which is a legal case). We don't need to worry about alignment because pgd_addr_end() can handle it. Cc: stable@vger.kernel.org Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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 reStructuredText 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.