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Commit 7614ff32 authored by Balbir Singh's avatar Balbir Singh Committed by Michael Ellerman
Browse files

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: default avatarBalbir Singh <bsingharora@gmail.com>
[mpe: Split down to PAGE_SIZE, not 2MB, rewrite change log]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent cd65d697

arch/powerpc/mm/pgtable-radix.c

+66 −1
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/sched/mm.h>

#include <linux/memblock.h>

#include <linux/of_fdt.h>

#include <linux/mm.h>



#include <asm/pgtable.h>

#include <asm/pgalloc.h>
@@ -110,6 +111,49 @@ int radix__map_kernel_page(unsigned long ea, unsigned long pa, 
	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;

arch/powerpc/mm/pgtable_64.c

+3 −1
Original line number Diff line number Diff line
@@ -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