diff options
Diffstat (limited to 'arch/arm/mm/mmu.c')
| -rw-r--r-- | arch/arm/mm/mmu.c | 51 |
1 files changed, 46 insertions, 5 deletions
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index ab14b79b03f0..8348ed6b2efe 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -1406,8 +1406,8 @@ void __init early_paging_init(const struct machine_desc *mdesc, return; /* remap kernel code and data */ - map_start = init_mm.start_code; - map_end = init_mm.brk; + map_start = init_mm.start_code & PMD_MASK; + map_end = ALIGN(init_mm.brk, PMD_SIZE); /* get a handle on things... */ pgd0 = pgd_offset_k(0); @@ -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 */ - phys = __pa(map_start) & PMD_MASK; + /* + * 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(); } |