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97e3d26b |
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27-Oct-2022 |
Peter Zijlstra <peterz@infradead.org> |
x86/mm: Randomize per-cpu entry area Seth found that the CPU-entry-area; the piece of per-cpu data that is mapped into the userspace page-tables for kPTI is not subject to any randomization -- irrespective of kASLR settings. On x86_64 a whole P4D (512 GB) of virtual address space is reserved for this structure, which is plenty large enough to randomize things a little. As such, use a straight forward randomization scheme that avoids duplicates to spread the existing CPUs over the available space. [ bp: Fix le build. ] Reported-by: Seth Jenkins <sethjenkins@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de>
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186525bd |
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29-Nov-2019 |
Ingo Molnar <mingo@kernel.org> |
mm, x86/mm: Untangle address space layout definitions from basic pgtable type definitions - Untangle the somewhat incestous way of how VMALLOC_START is used all across the kernel, but is, on x86, defined deep inside one of the lowest level page table headers. It doesn't help that vmalloc.h only includes a single asm header: #include <asm/page.h> /* pgprot_t */ So there was no existing cross-arch way to decouple address layout definitions from page.h details. I used this: #ifndef VMALLOC_START # include <asm/vmalloc.h> #endif This way every architecture that wants to simplify page.h can do so. - Also on x86 we had a couple of LDT related inline functions that used the late-stage address space layout positions - but these could be uninlined without real trouble - the end result is cleaner this way as well. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Rik van Riel <riel@redhat.com> Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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