Subject: [PATCH v1 4/8] powerpc/vmlinux.lds: Align __init_begin to 16M

From: Balbir Singh <[email-masked]>
Date: Thu, 25 May 2017 13:36:46 +1000

For CONFIG_STRICT_KERNEL_RWX align __init_begin to 16M.
We use 16M since its the larger of 2M on radix and 16M
on hash for our linear mapping. The plan is to have
.text, .rodata and everything upto __init_begin marked
as RX. Note we still have executable read only data.
We could further align read only data to another 16M
boundary, but then the linker starts using stubs and
that breaks our assembler code in head_64.S

We don't use multi PT_LOAD in PHDRS because we are
not sure if all bootloaders support them

Signed-off-by: Balbir Singh <[email-masked]>
---
 arch/powerpc/kernel/vmlinux.lds.S | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 2f793be..3973829 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -8,6 +8,12 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+#define STRICT_ALIGN_SIZE	(1 << 24)
+#else
+#define STRICT_ALIGN_SIZE	PAGE_SIZE
+#endif
+
 ENTRY(_stext)
 
 PHDRS {
@@ -132,7 +138,7 @@ SECTIONS
 	PROVIDE32 (etext = .);
 
 	/* Read-only data */
-	RODATA
+	RO_DATA(PAGE_SIZE)
 
 	EXCEPTION_TABLE(0)
 
@@ -149,7 +155,7 @@ SECTIONS
 /*
  * Init sections discarded at runtime
  */
-	. = ALIGN(PAGE_SIZE);
+	. = ALIGN(STRICT_ALIGN_SIZE);
 	__init_begin = .;
 	INIT_TEXT_SECTION(PAGE_SIZE) :kernel
 
-- 
2.9.3