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  • linux-arm
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  • linux-dm
  • arch
  • x86
  • boot
  • compressed
  • pgtable_64.c
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  • Kirill A. Shutemov's avatar
    x86/boot/compressed/64: Fix boot on machines with broken E820 table · 0a46fff2
    Kirill A. Shutemov authored Aug 13, 2019
    BIOS on Samsung 500C Chromebook reports very rudimentary E820 table that
    consists of 2 entries:
    
      BIOS-e820: [mem 0x0000000000000000-0x0000000000000fff] usable
      BIOS-e820: [mem 0x00000000fffff000-0x00000000ffffffff] reserved
    
    It breaks logic in find_trampoline_placement(): bios_start lands on the
    end of the first 4k page and trampoline start gets placed below 0.
    
    Detect underflow and don't touch bios_start for such cases. It makes
    kernel ignore E820 table on machines that doesn't have two usable pages
    below BIOS_START_MAX.
    
    Fixes: 1b3a6264
    
     ("x86/boot/compressed/64: Validate trampoline placement against E820")
    Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: x86-ml <x86@kernel.org>
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=203463
    Link: https://lkml.kernel.org/r/20190813131654.24378-1-kirill.shutemov@linux.intel.com
    0a46fff2