linux-kernel - [Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP

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Date: Fri, 10 May 2024 02:04:22 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: mpe@...erman.id.au,
	npiggin@...il.com,
	christophe.leroy@...roup.eu,
	aneesh.kumar@...nel.org,
	naveen.n.rao@...ux.ibm.com,
	arnd@...db.de,
	rppt@...nel.org,
	anshuman.khandual@....com
Cc: linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	linux-mm@...ck.org,
	Wei Yang <richard.weiyang@...il.com>
Subject: [Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

When CONFIG_ARCH_KEEP_MEMBLOCK not set, we expect to discard related
code and data. But it doesn't until CONFIG_MEMORY_HOTPLUG not set
neither.

This patch puts memblock's .text/.data into its own section, so that it
only depends on CONFIG_ARCH_KEEP_MEMBLOCK to discard related code and
data.

After this, from the log message in mem_init_print_info(), init size
increase from 2420K to 2432K on arch x86.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>

---
v2: fix orphan section for powerpc
---
 arch/powerpc/kernel/vmlinux.lds.S |  1 +
 include/asm-generic/vmlinux.lds.h | 14 +++++++++++++-
 include/linux/memblock.h          |  8 ++++----
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index f420df7888a7..d6d33bec597a 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -125,6 +125,7 @@ SECTIONS
 		*(.text.asan.* .text.tsan.*)
 		MEM_KEEP(init.text)
 		MEM_KEEP(exit.text)
+		MEMBLOCK_KEEP(init.text)
 	} :text
 
 	. = ALIGN(PAGE_SIZE);
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f7749d0f2562..775c5eedb9e6 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -147,6 +147,14 @@
 #define MEM_DISCARD(sec) *(.mem##sec)
 #endif
 
+#if defined(CONFIG_ARCH_KEEP_MEMBLOCK)
+#define MEMBLOCK_KEEP(sec)    *(.mb##sec)
+#define MEMBLOCK_DISCARD(sec)
+#else
+#define MEMBLOCK_KEEP(sec)
+#define MEMBLOCK_DISCARD(sec) *(.mb##sec)
+#endif
+
 #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
 #define KEEP_PATCHABLE		KEEP(*(__patchable_function_entries))
 #define PATCHABLE_DISCARDS
@@ -356,6 +364,7 @@
 	*(.ref.data)							\
 	*(.data..shared_aligned) /* percpu related */			\
 	MEM_KEEP(init.data*)						\
+	MEMBLOCK_KEEP(init.data*)					\
 	*(.data.unlikely)						\
 	__start_once = .;						\
 	*(.data.once)							\
@@ -573,6 +582,7 @@
 		*(.ref.text)						\
 		*(.text.asan.* .text.tsan.*)				\
 	MEM_KEEP(init.text*)						\
+	MEMBLOCK_KEEP(init.text*)					\
 
 
 /* sched.text is aling to function alignment to secure we have same
@@ -680,6 +690,7 @@
 	KEEP(*(SORT(___kentry+*)))					\
 	*(.init.data .init.data.*)					\
 	MEM_DISCARD(init.data*)						\
+	MEMBLOCK_DISCARD(init.data*)					\
 	KERNEL_CTORS()							\
 	MCOUNT_REC()							\
 	*(.init.rodata .init.rodata.*)					\
@@ -706,7 +717,8 @@
 #define INIT_TEXT							\
 	*(.init.text .init.text.*)					\
 	*(.text.startup)						\
-	MEM_DISCARD(init.text*)
+	MEM_DISCARD(init.text*)						\
+	MEMBLOCK_DISCARD(init.text*)
 
 #define EXIT_DATA							\
 	*(.exit.data .exit.data.*)					\
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index e2082240586d..3e1f1d42dde7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -100,13 +100,13 @@ struct memblock {
 
 extern struct memblock memblock;
 
+#define __init_memblock        __section(".mbinit.text") __cold notrace \
+						  __latent_entropy
+#define __initdata_memblock    __section(".mbinit.data")
+
 #ifndef CONFIG_ARCH_KEEP_MEMBLOCK
-#define __init_memblock __meminit
-#define __initdata_memblock __meminitdata
 void memblock_discard(void);
 #else
-#define __init_memblock
-#define __initdata_memblock
 static inline void memblock_discard(void) {}
 #endif
 
-- 
2.34.1