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The merge resolution to deal with the conflict between commitsea72ce5da2("x86/kaslr: Expose and use the end of the physical memory address space") and99185c10d5("resource, kunit: add test case for region_intersects()") ended up being broken in configurations didn't define a MAX_PHYSMEM_BITS and that had a 32-bit 'phys_addr_t'. The fallback to using all bits set (ie "(-1ULL)") ended up causing a build error: kernel/resource.c: In function ‘gfr_start’: include/linux/minmax.h:93:30: error: conversion from ‘long long unsigned int’ to ‘resource_size_t’ {aka ‘unsigned int’} changes value from ‘18446744073709551615’ to ‘4294967295’ [-Werror=overflow] this was reported by Geert for m68k, but he points out that it happens on other 32-bit architectures too, eg mips, xtensa, parisc, and powerpc. Limiting 'PHYSMEM_END' to a 'phys_addr_t' (which is the same as 'resource_size_t') fixes the build, but Geert points out that it will then cause a silent overflow in mm/sparse.c: unsigned long max_sparsemem_pfn = (PHYSMEM_END + 1) >> PAGE_SHIFT; so we actually do want PHYSMEM_END to be defined a 64-bit type - just not all ones, and not larger than 'phys_addr_t'. The proper fix is probably to not have some kind of default fallback at all, but just make sure every architecture has a valid MAX_PHYSMEM_BITS. But in the meantime, this just applies the rule that PHYSMEM_END is the largest value that fits in a 'phys_addr_t', but does not have the high bit set in 64 bits. Ugly, ugly. Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Huang Ying <ying.huang@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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.