kbuild: -ffunction-sections fix for archs with conflicting sections

Enabling -ffunction-sections modified the generic linker script to
pull .text.* sections into regular TEXT_TEXT section, conflicting
with some architectures. Revert that change and require archs that
enable the option to ensure they have no conflicting section names,
and do the appropriate merging.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Fixes: b67067f1176d ("kbuild: allow archs to select link dead code/data elimination")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>

arch/Kconfig

@@ -478,7 +478,9 @@ config LD_DEAD_CODE_DATA_ELIMINATION
 	  This requires that the arch annotates or otherwise protects
 	  its external entry points from being discarded. Linker scripts
 	  must also merge .text.*, .data.*, and .bss.* correctly into
-	  output sections.
+	  output sections. Care must be taken not to pull in unrelated
+	  sections (e.g., '.text.init'). Typically '.' in section names
+	  is used to distinguish them from label names / C identifiers.
 
 config HAVE_CONTEXT_TRACKING
 	bool

include/asm-generic/vmlinux.lds.h

@@ -198,9 +198,9 @@
 
 /*
  * .data section
- * -fdata-sections generates .data.identifier which needs to be pulled in
- * with .data, but don't want to pull in .data..stuff which has its own
- * requirements. Same for bss.
+ * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections generates
+ * .data.identifier which needs to be pulled in with .data, but don't want to
+ * pull in .data..stuff which has its own requirements. Same for bss.
  */
 #define DATA_DATA							\
 	*(.data .data.[0-9a-zA-Z_]*)					\
@@ -434,10 +434,15 @@
 	}
 
 /* .text section. Map to function alignment to avoid address changes
- * during second ld run in second ld pass when generating System.map */
+ * during second ld run in second ld pass when generating System.map
+ * LD_DEAD_CODE_DATA_ELIMINATION option enables -ffunction-sections generates
+ * .text.identifier which needs to be pulled in with .text , but some
+ * architectures define .text.foo which is not intended to be pulled in here.
+ * Those enabling LD_DEAD_CODE_DATA_ELIMINATION must ensure they don't have
+ * conflicting section names, and must pull in .text.[0-9a-zA-Z_]* */
 #define TEXT_TEXT							\
 		ALIGN_FUNCTION();					\
-		*(.text.hot .text .text.fixup .text.unlikely .text.*)	\
+		*(.text.hot .text .text.fixup .text.unlikely)		\
 		*(.ref.text)						\
 	MEM_KEEP(init.text)						\
 	MEM_KEEP(exit.text)						\