Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
94133e46a0
For EFI with the 'efi=old_map' kernel option specified, the kernel will panic when KASLR is enabled: BUG: unable to handle kernel paging request at 000000007febd57e IP: 0x7febd57e PGD 1025a067 PUD 0 Oops: 0010 [#1] SMP Call Trace: efi_enter_virtual_mode() start_kernel() x86_64_start_reservations() x86_64_start_kernel() start_cpu() The root cause is that the identity mapping is not built correctly in the 'efi=old_map' case. On 'nokaslr' kernels, PAGE_OFFSET is 0xffff880000000000 which is PGDIR_SIZE aligned. We can borrow the PUD table from the direct mappings safely. Given a physical address X, we have pud_index(X) == pud_index(__va(X)). However, on KASLR kernels, PAGE_OFFSET is PUD_SIZE aligned. For a given physical address X, pud_index(X) != pud_index(__va(X)). We can't just copy the PGD entry from direct mapping to build identity mapping, instead we need to copy the PUD entries one by one from the direct mapping. Fix it. Signed-off-by: Baoquan He <bhe@redhat.com> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Bhupesh Sharma <bhsharma@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Young <dyoung@redhat.com> Cc: Frank Ramsay <frank.ramsay@hpe.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russ Anderson <rja@sgi.com> Cc: Thomas Garnier <thgarnie@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20170526113652.21339-5-matt@codeblueprint.co.uk [ Fixed and reworded the changelog and code comments to be more readable. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.