linux-kernel - [PATCH v4 8/9] riscv: add alignment for text, rodata and data sections

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Date:   Tue,  7 Apr 2020 22:46:53 +0800
From:   Zong Li <zong.li@...ive.com>
To:     palmer@...belt.com, paul.walmsley@...ive.com,
        aou@...s.berkeley.edu, mhiramat@...nel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Zong Li <zong.li@...ive.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: [PATCH v4 8/9] riscv: add alignment for text, rodata and data sections

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@...ive.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.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 620d81c372d9..4c5bae7ca01c 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.
  */
@@ -24,4 +25,16 @@ static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
 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)
-- 
2.26.0