[PATCH v2 2/5] kasan: Move generic KASAN page tables out of BSS too

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

Make sure that all KASAN page tables are emitted into the .pgtbl section
(provided that the arch has one - otherwise, fall back to page aligned
BSS)

This is needed because BSS itself is no longer accessible via the linear
map on arm64.

Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: kasan-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 include/linux/linkage.h |  4 ++++
 mm/kasan/init.c         | 10 +++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index b11660b706c5..53fe1f48fd28 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -39,6 +39,10 @@
 #define __page_aligned_data	__section(".data..page_aligned") __aligned(PAGE_SIZE)
 #define __page_aligned_bss	__section(".bss..page_aligned") __aligned(PAGE_SIZE)
 
+#ifndef __bss_pgtbl
+#define __bss_pgtbl		__page_aligned_bss
+#endif
+
 /*
  * For assembly routines.
  *
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index 9c880f607c6a..66a883887987 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -26,10 +26,10 @@
  *   - Latter it reused it as zero shadow to cover large ranges of memory
  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  */
-unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
+unsigned char kasan_early_shadow_page[PAGE_SIZE] __bss_pgtbl;
 
 #if CONFIG_PGTABLE_LEVELS > 4
-p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
+p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __bss_pgtbl;
 static inline bool kasan_p4d_table(pgd_t pgd)
 {
 	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
@@ -41,7 +41,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
-pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
+pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __bss_pgtbl;
 static inline bool kasan_pud_table(p4d_t p4d)
 {
 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
@@ -53,7 +53,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
-pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
+pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __bss_pgtbl;
 static inline bool kasan_pmd_table(pud_t pud)
 {
 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
@@ -65,7 +65,7 @@ static inline bool kasan_pmd_table(pud_t pud)
 }
 #endif
 pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
-	__page_aligned_bss;
+	__bss_pgtbl;
 
 static inline bool kasan_pte_table(pmd_t pmd)
 {
-- 
2.54.0.1032.g2f8565e1d1-goog