From: Balbir Singh <bsinghar...@gmail.com>
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 <bsinghar...@gmail.com>
[mpe: Split down to PAGE_SIZE, not 2MB, rewrite change log]
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/mm/pgtable-radix.c | 67 +++++++++++++++++++++++++++++++++++++++--
1 file changed, 65 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index b07e0008d02a..d2fd34a6f542 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>
@@ -113,7 +114,48 @@ int radix__map_kernel_page(unsigned long ea, unsigned long
pa,
#ifdef CONFIG_STRICT_KERNEL_RWX
void radix__mark_rodata_ro(void)
{
- pr_warn("Not yet implemented for radix\n");
+ 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;
+
+ if (!mmu_has_feature(MMU_FTR_KERNEL_RO)) {
+ pr_info("R/O rodata not supported\n");
+ return;
+ }
+
+ 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
@@ -132,6 +174,12 @@ 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) {
@@ -140,9 +188,12 @@ 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)
@@ -150,6 +201,18 @@ 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;
--
2.7.4
