[PATCH v3 1/2] arm64: mm: Enable CONT_SIZE aligned sections for 64k page kernels.

[Jeremy Linton]

This change allows ALIGN_RODATA for 64k and 16k kernels.
In the case of 64k/16k kernels it actually aligns to the CONT_SIZE (2M)
rather than the SECTION_SIZE (which is 512M/32M). This makes it generally
more useful, given contiguous hit enabled kernels.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
---
 arch/arm64/Kconfig.debug        | 13 +++++++------
 arch/arm64/kernel/vmlinux.lds.S | 11 ++++++-----
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index e13c4bf..9d33d5e 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -59,15 +59,16 @@ config DEBUG_RODATA
           If in doubt, say Y
 
 config DEBUG_ALIGN_RODATA
-	depends on DEBUG_RODATA && ARM64_4K_PAGES
+	depends on DEBUG_RODATA
 	bool "Align linker sections up to SECTION_SIZE"
 	help
 	  If this option is enabled, sections that may potentially be marked as
-	  read only or non-executable will be aligned up to the section size of
-	  the kernel. This prevents sections from being split into pages and
-	  avoids a potential TLB penalty. The downside is an increase in
-	  alignment and potentially wasted space. Turn on this option if
-	  performance is more important than memory pressure.
+	  read only or non-executable will be aligned up to the section size
+	  or contiguous hint size of the kernel (2 MiB). This prevents sections
+	  from being split into pages and avoids a potential TLB penalty. The
+	  downside is an increase in alignment and potentially wasted space.
+	  Turn on this option if performance is more important than memory
+	  pressure.
 
 	  If in doubt, say N
 
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index b78a3c7..8f4fc2c 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -63,13 +63,14 @@ PECOFF_FILE_ALIGNMENT = 0x200;
 #endif
 
 #if defined(CONFIG_DEBUG_ALIGN_RODATA)
-#define ALIGN_DEBUG_RO			. = ALIGN(1<<SECTION_SHIFT);
-#define ALIGN_DEBUG_RO_MIN(min)		ALIGN_DEBUG_RO
+#if defined(CONFIG_ARM64_4K_PAGES)
+#define ALIGN_DEBUG_RO_MIN(min)		. = ALIGN(SECTION_SIZE);
+#else
+#define ALIGN_DEBUG_RO_MIN(min)		. = ALIGN(CONT_SIZE);
+#endif
 #elif defined(CONFIG_DEBUG_RODATA)
-#define ALIGN_DEBUG_RO			. = ALIGN(1<<PAGE_SHIFT);
-#define ALIGN_DEBUG_RO_MIN(min)		ALIGN_DEBUG_RO
+#define ALIGN_DEBUG_RO_MIN(min)		. = ALIGN(PAGE_SIZE);
 #else
-#define ALIGN_DEBUG_RO
 #define ALIGN_DEBUG_RO_MIN(min)		. = ALIGN(min);
 #endif
 
-- 
2.4.3