Merge branch 'x86/pti' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 PTI updates from Thomas Gleixner:
 "The Speck brigade sadly provides yet another large set of patches
  destroying the perfomance which we carefully built and preserved

   - PTI support for 32bit PAE. The missing counter part to the 64bit
     PTI code implemented by Joerg.

   - A set of fixes for the Global Bit mechanics for non PCID CPUs which
     were setting the Global Bit too widely and therefore possibly
     exposing interesting memory needlessly.

   - Protection against userspace-userspace SpectreRSB

   - Support for the upcoming Enhanced IBRS mode, which is preferred
     over IBRS. Unfortunately we dont know the performance impact of
     this, but it's expected to be less horrible than the IBRS
     hammering.

   - Cleanups and simplifications"

* 'x86/pti' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits)
  x86/mm/pti: Move user W+X check into pti_finalize()
  x86/relocs: Add __end_rodata_aligned to S_REL
  x86/mm/pti: Clone kernel-image on PTE level for 32 bit
  x86/mm/pti: Don't clear permissions in pti_clone_pmd()
  x86/mm/pti: Fix 32 bit PCID check
  x86/mm/init: Remove freed kernel image areas from alias mapping
  x86/mm/init: Add helper for freeing kernel image pages
  x86/mm/init: Pass unconverted symbol addresses to free_init_pages()
  mm: Allow non-direct-map arguments to free_reserved_area()
  x86/mm/pti: Clear Global bit more aggressively
  x86/speculation: Support Enhanced IBRS on future CPUs
  x86/speculation: Protect against userspace-userspace spectreRSB
  x86/kexec: Allocate 8k PGDs for PTI
  Revert "perf/core: Make sure the ring-buffer is mapped in all page-tables"
  x86/mm: Remove in_nmi() warning from vmalloc_fault()
  x86/entry/32: Check for VM86 mode in slow-path check
  perf/core: Make sure the ring-buffer is mapped in all page-tables
  x86/pti: Check the return value of pti_user_pagetable_walk_pmd()
  x86/pti: Check the return value of pti_user_pagetable_walk_p4d()
  x86/entry/32: Add debug code to check entry/exit CR3
  ...

1 files changed, 14 insertions, 2 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a790ef4be74e..3222193c46c6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6939,9 +6939,21 @@ unsigned long free_reserved_area(void *start, void *end, int poison, char *s)
 	start = (void *)PAGE_ALIGN((unsigned long)start);
 	end = (void *)((unsigned long)end & PAGE_MASK);
 	for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {
+		struct page *page = virt_to_page(pos);
+		void *direct_map_addr;
+
+		/*
+		 * 'direct_map_addr' might be different from 'pos'
+		 * because some architectures' virt_to_page()
+		 * work with aliases.  Getting the direct map
+		 * address ensures that we get a _writeable_
+		 * alias for the memset().
+		 */
+		direct_map_addr = page_address(page);
 		if ((unsigned int)poison <= 0xFF)
-			memset(pos, poison, PAGE_SIZE);
-		free_reserved_page(virt_to_page(pos));
+			memset(direct_map_addr, poison, PAGE_SIZE);
+
+		free_reserved_page(page);
 	}
 
 	if (pages && s)