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authorBalbir Singh <bsingharora@gmail.com>2017-06-29 03:04:09 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2017-07-04 11:37:39 +1000
commit7614ff3272a115a047139173cc04466e8132a1f2 (patch)
tree6215fd8d6460f772c73639a0c1459398067db360 /arch/powerpc/mm
parentcd65d69713349fc7b33fa9de2b32989b99c9fb39 (diff)
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>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/pgtable-radix.c67
-rw-r--r--arch/powerpc/mm/pgtable_64.c4
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 <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 @@ 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