Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm

Pull ARM updates from Russell King:
 "Included in this update:

   - perf updates from Will Deacon:

     The main changes are callchain stability fixes from Jean Pihet and
     event mapping and PMU name rework from Mark Rutland

     The latter is preparatory work for enabling some code re-use with
     arm64 in the future.

   - updates for nommu from Uwe Kleine-König:

     Two different fixes for the same problem making some ARM nommu
     configurations not boot since 3.6-rc1.  The problem is that
     user_addr_max returned the biggest available RAM address which
     makes some copy_from_user variants fail to read from XIP memory.

   - deprecate legacy OMAP DMA API, in preparation for it's removal.

     The popular drivers have been converted over, leaving a very small
     number of rarely used drivers, which hopefully can be converted
     during the next cycle with a bit more visibility (and hopefully
     people popping out of the woodwork to help test)

   - more tweaks for BE systems, particularly with the kernel image
     format.  In connection with this, I've cleaned up the way we
     generate the linker script for the decompressor.

   - removal of hard-coded assumptions of the kernel stack size, making
     everywhere depend on the value of THREAD_SIZE_ORDER.

   - MCPM updates from Nicolas Pitre.

   - Make it easier for proper CPU part number checks (which should
     always include the vendor field).

   - Assembly code optimisation - use the "bx" instruction when
     returning from a function on ARMv6+ rather than "mov pc, reg".

   - Save the last kernel misaligned fault location and report it via
     the procfs alignment file.

   - Clean up the way we create the initial stack frame, which is a
     repeated pattern in several different locations.

   - Support for 8-byte get_user(), needed for some DRM implementations.

   - mcs locking from Will Deacon.

   - Save and restore a few more Cortex-A9 registers (for errata
     workarounds)

   - Fix various aspects of the SWP emulation, and the ELF hwcap for the
     SWP instruction.

   - Update LPAE logic for pte_write and pmd_write to make it more
     correct.

   - Support for Broadcom Brahma15 CPU cores.

   - ARM assembly crypto updates from Ard Biesheuvel"

* 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm: (53 commits)
  ARM: add comments to the early page table remap code
  ARM: 8122/1: smp_scu: enable SCU standby support
  ARM: 8121/1: smp_scu: use macro for SCU enable bit
  ARM: 8120/1: crypto: sha512: add ARM NEON implementation
  ARM: 8119/1: crypto: sha1: add ARM NEON implementation
  ARM: 8118/1: crypto: sha1/make use of common SHA-1 structures
  ARM: 8113/1: remove remaining definitions of PLAT_PHYS_OFFSET from <mach/memory.h>
  ARM: 8111/1: Enable erratum 798181 for Broadcom Brahma-B15
  ARM: 8110/1: do CPU-specific init for Broadcom Brahma15 cores
  ARM: 8109/1: mm: Modify pte_write and pmd_write logic for LPAE
  ARM: 8108/1: mm: Introduce {pte,pmd}_isset and {pte,pmd}_isclear
  ARM: hwcap: disable HWCAP_SWP if the CPU advertises it has exclusives
  ARM: SWP emulation: only initialise on ARMv7 CPUs
  ARM: SWP emulation: always enable when SMP is enabled
  ARM: 8103/1: save/restore Cortex-A9 CP15 registers on suspend/resume
  ARM: 8098/1: mcs lock: implement wfe-based polling for MCS locking
  ARM: 8091/2: add get_user() support for 8 byte types
  ARM: 8097/1: unistd.h: relocate comments back to place
  ARM: 8096/1: Describe required sort order for textofs-y (TEXT_OFFSET)
  ARM: 8090/1: add revision info for PL310 errata 588369 and 727915
  ...

1 files changed, 43 insertions, 2 deletions

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 6e3ba8d112a2..8348ed6b2efe 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1434,23 +1434,64 @@ void __init early_paging_init(const struct machine_desc *mdesc,
 	dsb(ishst);
 	isb();
 
-	/* remap level 1 table */
+	/*
+	 * FIXME: This code is not architecturally compliant: we modify
+	 * the mappings in-place, indeed while they are in use by this
+	 * very same code.  This may lead to unpredictable behaviour of
+	 * the CPU.
+	 *
+	 * Even modifying the mappings in a separate page table does
+	 * not resolve this.
+	 *
+	 * The architecture strongly recommends that when a mapping is
+	 * changed, that it is changed by first going via an invalid
+	 * mapping and back to the new mapping.  This is to ensure that
+	 * no TLB conflicts (caused by the TLB having more than one TLB
+	 * entry match a translation) can occur.  However, doing that
+	 * here will result in unmapping the code we are running.
+	 */
+	pr_warn("WARNING: unsafe modification of in-place page tables - tainting kernel\n");
+	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+
+	/*
+	 * Remap level 1 table.  This changes the physical addresses
+	 * used to refer to the level 2 page tables to the high
+	 * physical address alias, leaving everything else the same.
+	 */
 	for (i = 0; i < PTRS_PER_PGD; pud0++, i++) {
 		set_pud(pud0,
 			__pud(__pa(pmd0) | PMD_TYPE_TABLE | L_PGD_SWAPPER));
 		pmd0 += PTRS_PER_PMD;
 	}
 
-	/* remap pmds for kernel mapping */
+	/*
+	 * Remap the level 2 table, pointing the mappings at the high
+	 * physical address alias of these pages.
+	 */
 	phys = __pa(map_start);
 	do {
 		*pmdk++ = __pmd(phys | pmdprot);
 		phys += PMD_SIZE;
 	} while (phys < map_end);
 
+	/*
+	 * Ensure that the above updates are flushed out of the cache.
+	 * This is not strictly correct; on a system where the caches
+	 * are coherent with each other, but the MMU page table walks
+	 * may not be coherent, flush_cache_all() may be a no-op, and
+	 * this will fail.
+	 */
 	flush_cache_all();
+
+	/*
+	 * Re-write the TTBR values to point them at the high physical
+	 * alias of the page tables.  We expect __va() will work on
+	 * cpu_get_pgd(), which returns the value of TTBR0.
+	 */
 	cpu_switch_mm(pgd0, &init_mm);
 	cpu_set_ttbr(1, __pa(pgd0) + TTBR1_OFFSET);
+
+	/* Finally flush any stale TLB values. */
 	local_flush_bp_all();
 	local_flush_tlb_all();
 }