From 7614ff3272a115a047139173cc04466e8132a1f2 Mon Sep 17 00:00:00 2001 From: Balbir Singh Date: Thu, 29 Jun 2017 03:04:09 +1000 Subject: [PATCH] powerpc/mm/radix: Implement STRICT_RWX/mark_rodata_ro() for Radix The Radix linear mapping code (create_physical_mapping()) tries to use the largest page size it can at each step. Currently the only reason it steps down to a smaller page size is if the start addr is unaligned (never happens in practice), or the end of memory is not aligned to a huge page boundary. To support STRICT_RWX we need to break the mapping at __init_begin, so that the text and rodata prior to that can be marked R_X and the regular pages after can be marked RW. Having done that we can now implement mark_rodata_ro() for Radix, knowing that we won't need to split any mappings. Signed-off-by: Balbir Singh [mpe: Split down to PAGE_SIZE, not 2MB, rewrite change log] Signed-off-by: Michael Ellerman --- arch/powerpc/mm/pgtable-radix.c | 67 ++++++++++++++++++++++++++++++++- arch/powerpc/mm/pgtable_64.c | 4 +- 2 files changed, 69 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c index 1342859552b1..8c13e4282308 100644 --- a/arch/powerpc/mm/pgtable-radix.c +++ b/arch/powerpc/mm/pgtable-radix.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include @@ -110,6 +111,49 @@ set_the_pte: return 0; } +#ifdef CONFIG_STRICT_KERNEL_RWX +void radix__mark_rodata_ro(void) +{ + unsigned long start = (unsigned long)_stext; + unsigned long end = (unsigned long)__init_begin; + unsigned long idx; + pgd_t *pgdp; + pud_t *pudp; + pmd_t *pmdp; + pte_t *ptep; + + start = ALIGN_DOWN(start, PAGE_SIZE); + end = PAGE_ALIGN(end); // aligns up + + pr_devel("marking ro start %lx, end %lx\n", start, end); + + for (idx = start; idx < end; idx += PAGE_SIZE) { + pgdp = pgd_offset_k(idx); + pudp = pud_alloc(&init_mm, pgdp, idx); + if (!pudp) + continue; + if (pud_huge(*pudp)) { + ptep = (pte_t *)pudp; + goto update_the_pte; + } + pmdp = pmd_alloc(&init_mm, pudp, idx); + if (!pmdp) + continue; + if (pmd_huge(*pmdp)) { + ptep = pmdp_ptep(pmdp); + goto update_the_pte; + } + ptep = pte_alloc_kernel(pmdp, idx); + if (!ptep) + continue; +update_the_pte: + radix__pte_update(&init_mm, idx, ptep, _PAGE_WRITE, 0, 0); + } + + radix__flush_tlb_kernel_range(start, end); +} +#endif /* CONFIG_STRICT_KERNEL_RWX */ + static inline void __meminit print_mapping(unsigned long start, unsigned long end, unsigned long size) @@ -125,6 +169,12 @@ static int __meminit create_physical_mapping(unsigned long start, { unsigned long vaddr, addr, mapping_size = 0; pgprot_t prot; + unsigned long max_mapping_size; +#ifdef CONFIG_STRICT_KERNEL_RWX + int split_text_mapping = 1; +#else + int split_text_mapping = 0; +#endif start = _ALIGN_UP(start, PAGE_SIZE); for (addr = start; addr < end; addr += mapping_size) { @@ -133,9 +183,12 @@ static int __meminit create_physical_mapping(unsigned long start, gap = end - addr; previous_size = mapping_size; + max_mapping_size = PUD_SIZE; +retry: if (IS_ALIGNED(addr, PUD_SIZE) && gap >= PUD_SIZE && - mmu_psize_defs[MMU_PAGE_1G].shift) + mmu_psize_defs[MMU_PAGE_1G].shift && + PUD_SIZE <= max_mapping_size) mapping_size = PUD_SIZE; else if (IS_ALIGNED(addr, PMD_SIZE) && gap >= PMD_SIZE && mmu_psize_defs[MMU_PAGE_2M].shift) @@ -143,6 +196,18 @@ static int __meminit create_physical_mapping(unsigned long start, else mapping_size = PAGE_SIZE; + if (split_text_mapping && (mapping_size == PUD_SIZE) && + (addr <= __pa_symbol(__init_begin)) && + (addr + mapping_size) >= __pa_symbol(_stext)) { + max_mapping_size = PMD_SIZE; + goto retry; + } + + if (split_text_mapping && (mapping_size == PMD_SIZE) && + (addr <= __pa_symbol(__init_begin)) && + (addr + mapping_size) >= __pa_symbol(_stext)) + mapping_size = PAGE_SIZE; + if (mapping_size != previous_size) { print_mapping(start, addr, previous_size); start = addr; diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c index fc2e6def2eb7..5c0b795d656c 100644 --- a/arch/powerpc/mm/pgtable_64.c +++ b/arch/powerpc/mm/pgtable_64.c @@ -500,7 +500,9 @@ void mark_rodata_ro(void) return; } - if (!radix_enabled()) + if (radix_enabled()) + radix__mark_rodata_ro(); + else hash__mark_rodata_ro(); } #endif -- 2.20.1