From 970d54f99ceac5bbf27929cb5ebfe18338ba1543 Mon Sep 17 00:00:00 2001 From: Russell Currey Date: Tue, 24 Dec 2019 17:41:25 +1100 Subject: powerpc/book3s64/hash: Disable 16M linear mapping size if not aligned With STRICT_KERNEL_RWX on in a relocatable kernel under the hash MMU, if the position the kernel is loaded at is not 16M aligned things go horribly wrong. Specifically hash__mark_initmem_nx() will call hash__change_memory_range() which then aligns down the start address, and due to the text not being 16M aligned causes some of the kernel text to be marked non-executable. We can avoid this when selecting the linear mapping size, so do so and print a warning. I tested this for various alignments and as long as the position is 64K aligned it's fine (the base requirement for powerpc). Signed-off-by: Russell Currey [mpe: Add details of the failure mode] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20191224064126.183670-1-ruscur@russell.cc --- arch/powerpc/mm/book3s64/hash_utils.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/mm/book3s64/hash_utils.c') diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index b30435c7d804..523d4d39d11e 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -652,6 +652,7 @@ static void init_hpte_page_sizes(void) static void __init htab_init_page_sizes(void) { + bool aligned = true; init_hpte_page_sizes(); if (!debug_pagealloc_enabled()) { @@ -659,7 +660,15 @@ static void __init htab_init_page_sizes(void) * Pick a size for the linear mapping. Currently, we only * support 16M, 1M and 4K which is the default */ - if (mmu_psize_defs[MMU_PAGE_16M].shift) + if (IS_ENABLED(STRICT_KERNEL_RWX) && + (unsigned long)_stext % 0x1000000) { + if (mmu_psize_defs[MMU_PAGE_16M].shift) + pr_warn("Kernel not 16M aligned, " + "disabling 16M linear map alignment"); + aligned = false; + } + + if (mmu_psize_defs[MMU_PAGE_16M].shift && aligned) mmu_linear_psize = MMU_PAGE_16M; else if (mmu_psize_defs[MMU_PAGE_1M].shift) mmu_linear_psize = MMU_PAGE_1M; -- cgit v1.2.3-59-g8ed1b