2002-10-16 13:45:21

by Matthew Wilcox

Subject: [PATCH] Allow compilation with -ffunction-sections

If you compile the kernel with -ffunction-sections, each function gets
put in a section .text.function_name. This collides with our current use
of .text.init. So here's a patch which converts x86 to use .init.text
instead.

I've tested it on x86 and it still frees 120k of ram, so it seems to work.
Other architectures will need to change their vmlinux.lds appropriately,
and may need other changes (arm, m68k seem to use .text.init verbatim).

diff -urpNX dontdiff linux-2.5.43/arch/i386/vmlinux.lds.S linux-2.5.43-willy/arch/i386/vmlinux.lds.S
--- linux-2.5.43/arch/i386/vmlinux.lds.S 2002-10-11 05:23:56.000000000 -0700
+++ linux-2.5.43-willy/arch/i386/vmlinux.lds.S 2002-10-16 06:34:00.000000000 -0700
@@ -41,11 +41,11 @@ SECTIONS

. = ALIGN(4096); /* Init code and data */
__init_begin = .;
- .text.init : { *(.text.init) }
- .data.init : { *(.data.init) }
+ .init.text : { *(.init.text) }
+ .init.data : { *(.init.data) }
. = ALIGN(16);
__setup_start = .;
- .setup.init : { *(.setup.init) }
+ .init.setup : { *(.init.setup) }
__setup_end = .;
__initcall_start = .;
.initcall.init : {
@@ -89,8 +89,8 @@ SECTIONS

/* Sections to be discarded */
/DISCARD/ : {
- *(.text.exit)
- *(.data.exit)
+ *(.exit.text)
+ *(.exit.data)
*(.exitcall.exit)
}

diff -urpNX dontdiff linux-2.5.43/include/linux/init.h linux-2.5.43-willy/include/linux/init.h
--- linux-2.5.43/include/linux/init.h 2002-08-13 19:54:03.000000000 -0700
+++ linux-2.5.43-willy/include/linux/init.h 2002-10-16 06:00:22.000000000 -0700
@@ -93,18 +93,18 @@ extern struct kernel_param __setup_start
* Mark functions and data as being only used at initialization
* or exit time.
*/
-#define __init __attribute__ ((__section__ (".text.init")))
-#define __exit __attribute__ ((unused, __section__(".text.exit")))
-#define __initdata __attribute__ ((__section__ (".data.init")))
-#define __exitdata __attribute__ ((unused, __section__ (".data.exit")))
-#define __initsetup __attribute__ ((unused,__section__ (".setup.init")))
+#define __init __attribute__ ((__section__ (".init.text")))
+#define __exit __attribute__ ((unused, __section__(".exit.text")))
+#define __initdata __attribute__ ((__section__ (".init.data")))
+#define __exitdata __attribute__ ((unused, __section__ (".exit.data")))
+#define __initsetup __attribute__ ((unused,__section__ (".init.setup")))
#define __init_call(level) __attribute__ ((unused,__section__ (".initcall" level ".init")))
#define __exit_call __attribute__ ((unused,__section__ (".exitcall.exit")))

/* For assembly routines */
-#define __INIT .section ".text.init","ax"
+#define __INIT .section ".init.text","ax"
#define __FINIT .previous
-#define __INITDATA .section ".data.init","aw"
+#define __INITDATA .section ".init.data","aw"

/**
* module_init() - driver initialization entry point

--
Revolutions do not require corporate support.

2002-10-16 16:38:09

by Kai Germaschewski

Subject: Re: [PATCH] Allow compilation with -ffunction-sections

On Wed, 16 Oct 2002, Matthew Wilcox wrote:

> If you compile the kernel with -ffunction-sections, each function gets
> put in a section .text.function_name. This collides with our current use
> of .text.init. So here's a patch which converts x86 to use .init.text
> instead.
>
> I've tested it on x86 and it still frees 120k of ram, so it seems to work.
> Other architectures will need to change their vmlinux.lds appropriately,
> and may need other changes (arm, m68k seem to use .text.init verbatim).

Just in case anybody feels bored, maybe someone wants to come up with a
include/asm-generic/vmlinux.lds.S (or a better name) which has the common
part of all the arch's vmlinux.lds.S - so we could make such changes like
you're proposing at one place in the future.

Since all vmlinux.lds.S get preprocessed by the C preprocessor, putting
an "#include <asm-generic/vmlinux.lds.S>" in there should be easy enough
instead of all the current duplication.

--Kai