[PATCH v2 1/5] arm64: Rename page table BSS section to .bss..pgtbl

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

Rename the .pgdir.bss section to .bss..pgtbl so that the compiler will
notice the leading ".bss" and mark it as NOBITS by default (rather than
PROGBITS, which would take up space in Image binary, forcing all of the
preceding BSS to be emitted into the image as well). This supersedes the
NOLOAD linker directive, which achieves the same thing, and can be
therefore be dropped.

Also, rename .pgdir to .pgtbl to be more generic, as page tables of
various levels will reside here.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/linkage.h | 2 ++
 arch/arm64/include/asm/mmu.h     | 2 --
 arch/arm64/kernel/vmlinux.lds.S  | 8 ++++----
 arch/arm64/mm/fixmap.c           | 6 +++---
 arch/arm64/mm/kasan_init.c       | 2 +-
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h
index 40bd17add539..8637f667667c 100644
--- a/arch/arm64/include/asm/linkage.h
+++ b/arch/arm64/include/asm/linkage.h
@@ -43,4 +43,6 @@
 	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
 	bti c ;
 
+#define __bss_pgtbl __section(".bss..pgtbl") __aligned(PAGE_SIZE)
+
 #endif
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index fb95754f2876..5e1211c540ab 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -13,8 +13,6 @@
 
 #ifndef __ASSEMBLER__
 
-#define __pgtbl_bss __section(".pgdir.bss") __aligned(PAGE_SIZE)
-
 #include <linux/refcount.h>
 #include <asm/cpufeature.h>
 
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 2b0ebfb30c63..d3ed59abab38 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -352,11 +352,11 @@ SECTIONS
 	BSS_SECTION(SBSS_ALIGN, 0, PAGE_SIZE)
 	__pi___bss_start = __bss_start;
 
-	/* fixmap BSS starts here - preceding data/BSS is omitted from the linear map */
-	.pgdir.bss (NOLOAD) : ALIGN(PAGE_SIZE) {
-		*(.pgdir.bss)
+	/* page table BSS starts here - preceding data/BSS is omitted from the linear map */
+	.pgtbl : ALIGN(PAGE_SIZE) {
+		*(.bss..pgtbl)
 	}
-	ASSERT(ADDR(.pgdir.bss) == __bss_stop, ".pgdir.bss must follow BSS")
+	ASSERT(ADDR(.pgtbl) == __bss_stop, ".pgtbl must follow BSS")
 
 	. = ALIGN(PAGE_SIZE);
 	__pi_init_pg_dir = .;
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
index 1a3bbd67dd76..f66a0016dd02 100644
--- a/arch/arm64/mm/fixmap.c
+++ b/arch/arm64/mm/fixmap.c
@@ -31,9 +31,9 @@ static_assert(NR_BM_PMD_TABLES == 1);
 
 #define BM_PTE_TABLE_IDX(addr)	__BM_TABLE_IDX(addr, PMD_SHIFT)
 
-static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __pgtbl_bss;
-static pmd_t bm_pmd[PTRS_PER_PMD] __pgtbl_bss __maybe_unused;
-static pud_t bm_pud[PTRS_PER_PUD] __pgtbl_bss __maybe_unused;
+static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __bss_pgtbl;
+static pmd_t bm_pmd[PTRS_PER_PMD] __bss_pgtbl __maybe_unused;
+static pud_t bm_pud[PTRS_PER_PUD] __bss_pgtbl __maybe_unused;
 
 static inline pte_t *fixmap_pte(unsigned long addr)
 {
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index dbf22cae82ee..3fcad956fdf7 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -214,7 +214,7 @@ asmlinkage void __init kasan_early_init(void)
 		 * shadow pud_t[]/p4d_t[], which could end up getting corrupted
 		 * when the linear region is mapped.
 		 */
-		static pte_t tbl[PTRS_PER_PTE] __pgtbl_bss;
+		static pte_t tbl[PTRS_PER_PTE] __bss_pgtbl;
 		pgd_t *pgdp = pgd_offset_k(KASAN_SHADOW_START);
 
 		set_pgd(pgdp, __pgd(__pa_symbol(tbl) | PGD_TYPE_TABLE));
-- 
2.54.0.1032.g2f8565e1d1-goog