[PATCH v2 5/9] riscv: add alignment for text, rodata and data sections

Zong Li
2020-03-09T08:22:52Z

The kernel mapping will tried to optimize its mapping by using bigger
size. In rv64, it tries to use PMD_SIZE, and tryies to use PGDIR_SIZE in
rv32. To ensure that the start address of these sections could fit the
mapping entry size, make them align to the biggest alignment.

Define a macro SECTION_ALIGN because the HPAGE_SIZE or PMD_SIZE, etc.,
are invisible in linker script.

This patch is prepared for STRICT_KERNEL_RWX support.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
arch/riscv/include/asm/set_memory.h | 13 +++++++++++++
arch/riscv/kernel/vmlinux.lds.S | 5 ++++-
2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
index a9783a878dca..a91f192063c2 100644
--- a/arch/riscv/include/asm/set_memory.h
+++ b/arch/riscv/include/asm/set_memory.h
@@ -6,6 +6,7 @@
#ifndef _ASM_RISCV_SET_MEMORY_H
#define _ASM_RISCV_SET_MEMORY_H

+#ifndef __ASSEMBLY__
/*
* Functions to change memory attributes.
*/
@@ -17,4 +18,16 @@ int set_memory_nx(unsigned long addr, int numpages);
int set_direct_map_invalid_noflush(struct page *page);
int set_direct_map_default_noflush(struct page *page);

+#endif /* __ASSEMBLY__ */
+
+#ifdef CONFIG_ARCH_HAS_STRICT_KERNEL_RWX
+#ifdef CONFIG_64BIT
+#define SECTION_ALIGN (1 << 21)
+#else
+#define SECTION_ALIGN (1 << 22)
+#endif
+#else /* !CONFIG_ARCH_HAS_STRICT_KERNEL_RWX */
+#define SECTION_ALIGN L1_CACHE_BYTES
+#endif /* CONFIG_ARCH_HAS_STRICT_KERNEL_RWX */
+
#endif /* _ASM_RISCV_SET_MEMORY_H */
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 02e948b620af..ef87deea0350 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -9,6 +9,7 @@
#include <asm/page.h>
#include <asm/cache.h>
#include <asm/thread_info.h>
+#include <asm/set_memory.h>

OUTPUT_ARCH(riscv)
ENTRY(_start)
@@ -36,6 +37,7 @@ SECTIONS
PERCPU_SECTION(L1_CACHE_BYTES)
__init_end = .;

+ . = ALIGN(SECTION_ALIGN);
.text : {
_text = .;
_stext = .;
@@ -53,13 +55,14 @@ SECTIONS

/* Start of data section */
_sdata = .;
- RO_DATA(L1_CACHE_BYTES)
+ RO_DATA(SECTION_ALIGN)
.srodata : {
*(.srodata*)
}

EXCEPTION_TABLE(0x10)

+ . = ALIGN(SECTION_ALIGN);
_data = .;

RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
--
2.25.1