Use separate sections for __dev/__cpu/__mem code/data

Introducing separate sections for __dev* (HOTPLUG),
__cpu* (HOTPLUG_CPU) and __mem* (MEMORY_HOTPLUG)
allows us to do a much more reliable Section mismatch
check in modpost. We are no longer dependent on the actual
configuration of for example HOTPLUG.

This has the effect that all users see much more
Section mismatch warnings than before because they
were almost all hidden when HOTPLUG was enabled.
The advantage of this is that when building a piece
of code then it is much more likely that the Section
mismatch errors are spotted and the warnings will be
felt less random of nature.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Adrian Bunk <bunk@kernel.org>

1 files changed, 82 insertions, 6 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index ae0166e8349..e0a56fb8f81 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -9,10 +9,46 @@
 /* Align . to a 8 byte boundary equals to maximum function alignment. */
 #define ALIGN_FUNCTION()  . = ALIGN(8)
 
+/* The actual configuration determine if the init/exit sections
+ * are handled as text/data or they can be discarded (which
+ * often happens at runtime)
+ */
+#ifdef CONFIG_HOTPLUG
+#define DEV_KEEP(sec)    *(.dev##sec)
+#define DEV_DISCARD(sec)
+#else
+#define DEV_KEEP(sec)
+#define DEV_DISCARD(sec) *(.dev##sec)
+#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+#define CPU_KEEP(sec)    *(.cpu##sec)
+#define CPU_DISCARD(sec)
+#else
+#define CPU_KEEP(sec)
+#define CPU_DISCARD(sec) *(.cpu##sec)
+#endif
+
+#if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_ACPI_HOTPLUG_MEMORY) \
+	|| defined(CONFIG_ACPI_HOTPLUG_MEMORY_MODULE)
+#define MEM_KEEP(sec)    *(.mem##sec)
+#define MEM_DISCARD(sec)
+#else
+#define MEM_KEEP(sec)
+#define MEM_DISCARD(sec) *(.mem##sec)
+#endif
+
+
 /* .data section */
 #define DATA_DATA							\
 	*(.data)							\
 	*(.data.init.refok)						\
+	DEV_KEEP(init.data)						\
+	DEV_KEEP(exit.data)						\
+	CPU_KEEP(init.data)						\
+	CPU_KEEP(exit.data)						\
+	MEM_KEEP(init.data)						\
+	MEM_KEEP(exit.data)						\
 	. = ALIGN(8);							\
 	VMLINUX_SYMBOL(__start___markers) = .;				\
 	*(__markers)							\
@@ -132,6 +168,16 @@
 		*(__ksymtab_strings)					\
 	}								\
 									\
+	/* __*init sections */						\
+	__init_rodata : AT(ADDR(__init_rodata) - LOAD_OFFSET) {		\
+		DEV_KEEP(init.rodata)					\
+		DEV_KEEP(exit.rodata)					\
+		CPU_KEEP(init.rodata)					\
+		CPU_KEEP(exit.rodata)					\
+		MEM_KEEP(init.rodata)					\
+		MEM_KEEP(exit.rodata)					\
+	}								\
+									\
 	/* Built-in module parameters. */				\
 	__param : AT(ADDR(__param) - LOAD_OFFSET) {			\
 		VMLINUX_SYMBOL(__start___param) = .;			\
@@ -139,7 +185,6 @@
 		VMLINUX_SYMBOL(__stop___param) = .;			\
 		VMLINUX_SYMBOL(__end_rodata) = .;			\
 	}								\
-									\
 	. = ALIGN((align));
 
 /* RODATA provided for backward compatibility.
@@ -159,7 +204,14 @@
 		ALIGN_FUNCTION();					\
 		*(.text)						\
 		*(.text.init.refok)					\
-		*(.exit.text.refok)
+		*(.exit.text.refok)					\
+	DEV_KEEP(init.text)						\
+	DEV_KEEP(exit.text)						\
+	CPU_KEEP(init.text)						\
+	CPU_KEEP(exit.text)						\
+	MEM_KEEP(init.text)						\
+	MEM_KEEP(exit.text)
+
 
 /* sched.text is aling to function alignment to secure we have same
  * address even at second ld pass when generating System.map */
@@ -184,11 +236,35 @@
 		VMLINUX_SYMBOL(__kprobes_text_end) = .;
 
 /* init and exit section handling */
-#define INIT_TEXT *(.init.text)
-#define INIT_DATA *(.init.data)
-#define EXIT_TEXT *(.exit.text)
-#define EXIT_DATA *(.exit.data)
+#define INIT_DATA							\
+	*(.init.data)							\
+	DEV_DISCARD(init.data)						\
+	DEV_DISCARD(init.rodata)					\
+	CPU_DISCARD(init.data)						\
+	CPU_DISCARD(init.rodata)					\
+	MEM_DISCARD(init.data)						\
+	MEM_DISCARD(init.rodata)
+
+#define INIT_TEXT							\
+	*(.init.text)							\
+	DEV_DISCARD(init.text)						\
+	CPU_DISCARD(init.text)						\
+	MEM_DISCARD(init.text)
+
+#define EXIT_DATA							\
+	*(.exit.data)							\
+	DEV_DISCARD(exit.data)						\
+	DEV_DISCARD(exit.rodata)					\
+	CPU_DISCARD(exit.data)						\
+	CPU_DISCARD(exit.rodata)					\
+	MEM_DISCARD(exit.data)						\
+	MEM_DISCARD(exit.rodata)
 
+#define EXIT_TEXT							\
+	*(.exit.text)							\
+	DEV_DISCARD(exit.text)						\
+	CPU_DISCARD(exit.text)						\
+	MEM_DISCARD(exit.text)
 
 		/* DWARF debug sections.
 		Symbols in the DWARF debugging sections are relative to