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 <bsingharora@gmail.com> [mpe: Split down to PAGE_SIZE, not 2MB, rewrite change log] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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@ -11,6 +11,7 @@
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#include <linux/sched/mm.h>
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#include <linux/memblock.h>
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#include <linux/of_fdt.h>
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#include <linux/mm.h>
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#include <asm/pgtable.h>
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#include <asm/pgalloc.h>
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@ -110,6 +111,49 @@ set_the_pte:
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return 0;
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}
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#ifdef CONFIG_STRICT_KERNEL_RWX
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void radix__mark_rodata_ro(void)
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{
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unsigned long start = (unsigned long)_stext;
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unsigned long end = (unsigned long)__init_begin;
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unsigned long idx;
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pgd_t *pgdp;
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pud_t *pudp;
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pmd_t *pmdp;
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pte_t *ptep;
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start = ALIGN_DOWN(start, PAGE_SIZE);
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end = PAGE_ALIGN(end); // aligns up
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pr_devel("marking ro start %lx, end %lx\n", start, end);
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for (idx = start; idx < end; idx += PAGE_SIZE) {
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pgdp = pgd_offset_k(idx);
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pudp = pud_alloc(&init_mm, pgdp, idx);
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if (!pudp)
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continue;
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if (pud_huge(*pudp)) {
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ptep = (pte_t *)pudp;
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goto update_the_pte;
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}
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pmdp = pmd_alloc(&init_mm, pudp, idx);
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if (!pmdp)
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continue;
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if (pmd_huge(*pmdp)) {
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ptep = pmdp_ptep(pmdp);
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goto update_the_pte;
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}
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ptep = pte_alloc_kernel(pmdp, idx);
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if (!ptep)
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continue;
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update_the_pte:
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radix__pte_update(&init_mm, idx, ptep, _PAGE_WRITE, 0, 0);
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}
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radix__flush_tlb_kernel_range(start, end);
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}
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#endif /* CONFIG_STRICT_KERNEL_RWX */
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static inline void __meminit print_mapping(unsigned long start,
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unsigned long end,
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unsigned long size)
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@ -125,6 +169,12 @@ static int __meminit create_physical_mapping(unsigned long start,
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{
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unsigned long vaddr, addr, mapping_size = 0;
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pgprot_t prot;
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unsigned long max_mapping_size;
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#ifdef CONFIG_STRICT_KERNEL_RWX
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int split_text_mapping = 1;
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#else
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int split_text_mapping = 0;
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#endif
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start = _ALIGN_UP(start, PAGE_SIZE);
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for (addr = start; addr < end; addr += mapping_size) {
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@ -133,9 +183,12 @@ static int __meminit create_physical_mapping(unsigned long start,
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gap = end - addr;
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previous_size = mapping_size;
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max_mapping_size = PUD_SIZE;
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retry:
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if (IS_ALIGNED(addr, PUD_SIZE) && gap >= PUD_SIZE &&
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mmu_psize_defs[MMU_PAGE_1G].shift)
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mmu_psize_defs[MMU_PAGE_1G].shift &&
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PUD_SIZE <= max_mapping_size)
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mapping_size = PUD_SIZE;
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else if (IS_ALIGNED(addr, PMD_SIZE) && gap >= PMD_SIZE &&
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mmu_psize_defs[MMU_PAGE_2M].shift)
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@ -143,6 +196,18 @@ static int __meminit create_physical_mapping(unsigned long start,
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else
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mapping_size = PAGE_SIZE;
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if (split_text_mapping && (mapping_size == PUD_SIZE) &&
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(addr <= __pa_symbol(__init_begin)) &&
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(addr + mapping_size) >= __pa_symbol(_stext)) {
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max_mapping_size = PMD_SIZE;
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goto retry;
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}
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if (split_text_mapping && (mapping_size == PMD_SIZE) &&
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(addr <= __pa_symbol(__init_begin)) &&
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(addr + mapping_size) >= __pa_symbol(_stext))
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mapping_size = PAGE_SIZE;
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if (mapping_size != previous_size) {
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print_mapping(start, addr, previous_size);
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start = addr;
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@ -500,7 +500,9 @@ void mark_rodata_ro(void)
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return;
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}
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if (!radix_enabled())
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if (radix_enabled())
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radix__mark_rodata_ro();
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else
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hash__mark_rodata_ro();
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}
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#endif
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