[PATCH 2/2] linker script: unify usage of discard definition

From: Tejun Heo
Date: Wed Jul 08 2009 - 05:27:51 EST

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Discarded sections in different archs share some commonality but have
considerable differences. This led to linker script for each arch
implementing its own /DISCARD/ definition, which makes maintaining
tedious and adding new entries error-prone.

This patch makes all linker scripts to move discard definitions to the
end of the linker script and use the common DISCARDS macro. As ld
uses the first matching section definition, archs can include default
discarded sections by including them earlier in the linker script.

ia64 is notable because it first throws away some ia64 specific
subsections and then include the rest of the sections into the final
image, so those sections must be discarded before the inclusion.

defconfig compile tested for x86, x86-64, powerpc, powerpc64, ia64,
alpha, sparc, sparc64 and s390. Michal Simek tested microblaze.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Acked-by: Paul Mundt <lethal@xxxxxxxxxxxx>
Acked-by: Mike Frysinger <vapier@xxxxxxxxxx>
Tested-by: Michal Simek <monstr@xxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: Michal Simek <monstr@xxxxxxxxx>
Cc: microblaze-uclinux@xxxxxxxxxxxxxx
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
---
ia64 needed some massaging to get it working.

arch/alpha/kernel/vmlinux.lds.S | 10 ++--------
arch/avr32/kernel/vmlinux.lds.S | 10 +++-------
arch/blackfin/kernel/vmlinux.lds.S | 6 +-----
arch/cris/kernel/vmlinux.lds.S | 10 ++--------
arch/frv/kernel/vmlinux.lds.S | 2 +-
arch/h8300/kernel/vmlinux.lds.S | 6 ++----
arch/ia64/kernel/vmlinux.lds.S | 17 ++++++++---------
arch/m32r/kernel/vmlinux.lds.S | 11 +++--------
arch/m68k/kernel/vmlinux-std.lds | 11 +++--------
arch/m68k/kernel/vmlinux-sun3.lds | 10 ++--------
arch/m68knommu/kernel/vmlinux.lds.S | 8 +-------
arch/microblaze/kernel/vmlinux.lds.S | 2 +-
arch/mips/kernel/vmlinux.lds.S | 22 ++++++++++------------
arch/mn10300/kernel/vmlinux.lds.S | 9 +++------
arch/parisc/kernel/vmlinux.lds.S | 9 ++++-----
arch/powerpc/kernel/vmlinux.lds.S | 10 +++-------
arch/s390/kernel/vmlinux.lds.S | 10 +++-------
arch/sh/kernel/vmlinux.lds.S | 11 ++++-------
arch/sparc/kernel/vmlinux.lds.S | 9 ++-------
arch/um/include/asm/common.lds.S | 5 -----
arch/um/kernel/dyn.lds.S | 2 +-
arch/um/kernel/uml.lds.S | 2 +-
arch/x86/kernel/vmlinux.lds.S | 11 ++++-------
arch/xtensa/kernel/vmlinux.lds.S | 14 ++++----------
include/asm-generic/vmlinux.lds.h | 18 ++++++++++++------
25 files changed, 80 insertions(+), 155 deletions(-)

Index: work/arch/alpha/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/alpha/kernel/vmlinux.lds.S
+++ work/arch/alpha/kernel/vmlinux.lds.S
@@ -134,14 +134,6 @@ SECTIONS
__bss_stop = .;
_end = .;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
.mdebug 0 : {
*(.mdebug)
}
@@ -151,4 +143,6 @@ SECTIONS

STABS_DEBUG
DWARF_DEBUG
+
+ DISCARDS
}
Index: work/arch/avr32/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/avr32/kernel/vmlinux.lds.S
+++ work/arch/avr32/kernel/vmlinux.lds.S
@@ -124,15 +124,11 @@ SECTIONS
_end = .;
}

+ DWARF_DEBUG
+
/* When something in the kernel is NOT compiled as a module, the module
* cleanup code and data are put into these segments. Both can then be
* thrown away, as cleanup code is never called unless it's a module.
*/
- /DISCARD/ : {
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
- DWARF_DEBUG
+ DISCARDS
}
Index: work/arch/blackfin/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/blackfin/kernel/vmlinux.lds.S
+++ work/arch/blackfin/kernel/vmlinux.lds.S
@@ -277,9 +277,5 @@ SECTIONS

DWARF_DEBUG

- /DISCARD/ :
- {
- *(.exitcall.exit)
- *(.discard)
- }
+ DISCARDS
}
Index: work/arch/cris/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/cris/kernel/vmlinux.lds.S
+++ work/arch/cris/kernel/vmlinux.lds.S
@@ -140,13 +140,7 @@ SECTIONS
_end = .;
__end = .;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
dram_end = dram_start + (CONFIG_ETRAX_DRAM_SIZE - __CONFIG_ETRAX_VMEM_SIZE)*1024*1024;
+
+ DISCARDS
}
Index: work/arch/frv/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/frv/kernel/vmlinux.lds.S
+++ work/arch/frv/kernel/vmlinux.lds.S
@@ -178,7 +178,7 @@ SECTIONS

.comment 0 : { *(.comment) }

- /DISCARD/ : { *(.discard) }
+ DISCARDS
}

__kernel_image_size_no_bss = __bss_start - __kernel_image_start;
Index: work/arch/h8300/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/h8300/kernel/vmlinux.lds.S
+++ work/arch/h8300/kernel/vmlinux.lds.S
@@ -152,10 +152,6 @@ SECTIONS
__end = . ;
__ramstart = .;
}
- /DISCARD/ : {
- *(.exitcall.exit)
- *(.discard)
- }
.romfs :
{
*(.romfs*)
@@ -166,4 +162,6 @@ SECTIONS
COMMAND_START = . - 0x200 ;
__ramend = . ;
}
+
+ DISCARDS
}
Index: work/arch/ia64/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/ia64/kernel/vmlinux.lds.S
+++ work/arch/ia64/kernel/vmlinux.lds.S
@@ -24,15 +24,14 @@ PHDRS {
}
SECTIONS
{
- /* Sections to be discarded */
+ /* unwind exit sections must be discarded before the rest of the
+ sections get included. */
/DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
*(.IA_64.unwind.exit.text)
*(.IA_64.unwind_info.exit.text)
- }
+ *(.comment)
+ *(.note)
+ }

v = PAGE_OFFSET; /* this symbol is here to make debugging easier... */
phys_start = _start - LOAD_OFFSET;
@@ -317,7 +316,7 @@ SECTIONS
.debug_funcnames 0 : { *(.debug_funcnames) }
.debug_typenames 0 : { *(.debug_typenames) }
.debug_varnames 0 : { *(.debug_varnames) }
- /* These must appear regardless of . */
- /DISCARD/ : { *(.comment) }
- /DISCARD/ : { *(.note) }
+
+ /* Default discards */
+ DISCARDS
}
Index: work/arch/m32r/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/m32r/kernel/vmlinux.lds.S
+++ work/arch/m32r/kernel/vmlinux.lds.S
@@ -120,14 +120,6 @@ SECTIONS

_end = . ;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
@@ -136,4 +128,7 @@ SECTIONS
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
+
+ /* Sections to be discarded */
+ DISCARDS
}
Index: work/arch/m68knommu/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/m68knommu/kernel/vmlinux.lds.S
+++ work/arch/m68knommu/kernel/vmlinux.lds.S
@@ -184,13 +184,6 @@ SECTIONS {
__init_end = .;
} > INIT

- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
.bss : {
. = ALIGN(4);
_sbss = . ;
@@ -201,5 +194,6 @@ SECTIONS {
_end = . ;
} > BSS

+ DISCARDS
}

Index: work/arch/microblaze/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/microblaze/kernel/vmlinux.lds.S
+++ work/arch/microblaze/kernel/vmlinux.lds.S
@@ -163,5 +163,5 @@ SECTIONS {
. = ALIGN(4096);
_end = .;

- /DISCARD/ : { *(.discard) }
+ DISCARDS
}
Index: work/arch/mips/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/mips/kernel/vmlinux.lds.S
+++ work/arch/mips/kernel/vmlinux.lds.S
@@ -176,18 +176,6 @@ SECTIONS

_end = . ;

- /* Sections to be discarded */
- /DISCARD/ : {
- *(.exitcall.exit)
- *(.discard)
-
- /* ABI crap starts here */
- *(.MIPS.options)
- *(.options)
- *(.pdr)
- *(.reginfo)
- }
-
/* These mark the ABI of the kernel for debuggers. */
.mdebug.abi32 : {
KEEP(*(.mdebug.abi32))
@@ -213,4 +201,14 @@ SECTIONS
*(.gptab.bss)
*(.gptab.sbss)
}
+
+ /* Sections to be discarded */
+ DISCARDS
+ /DISCARD/ : {
+ /* ABI crap starts here */
+ *(.MIPS.options)
+ *(.options)
+ *(.pdr)
+ *(.reginfo)
+ }
}
Index: work/arch/mn10300/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/mn10300/kernel/vmlinux.lds.S
+++ work/arch/mn10300/kernel/vmlinux.lds.S
@@ -115,13 +115,10 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
pg0 = .;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_CALL
- *(.discard)
- }
-
STABS_DEBUG

DWARF_DEBUG
+
+ /* Sections to be discarded */
+ DISCARDS
}
Index: work/arch/parisc/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/parisc/kernel/vmlinux.lds.S
+++ work/arch/parisc/kernel/vmlinux.lds.S
@@ -237,10 +237,12 @@ SECTIONS
/* freed after init ends here */
_end = . ;

+ STABS_DEBUG
+ .note 0 : { *(.note) }
+
/* Sections to be discarded */
+ DISCARDS
/DISCARD/ : {
- *(.exitcall.exit)
- *(.discard)
#ifdef CONFIG_64BIT
/* temporary hack until binutils is fixed to not emit these
* for static binaries
@@ -253,7 +255,4 @@ SECTIONS
*(.gnu.hash)
#endif
}
-
- STABS_DEBUG
- .note 0 : { *(.note) }
}
Index: work/arch/powerpc/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/powerpc/kernel/vmlinux.lds.S
+++ work/arch/powerpc/kernel/vmlinux.lds.S
@@ -37,13 +37,6 @@ jiffies = jiffies_64 + 4;
#endif
SECTIONS
{
- /* Sections to be discarded. */
- /DISCARD/ : {
- *(.exitcall.exit)
- *(.discard)
- EXIT_DATA
- }
-
. = KERNELBASE;

/*
@@ -299,4 +292,7 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
_end = . ;
PROVIDE32 (end = .);
+
+ /* Sections to be discarded. */
+ DISCARDS
}
Index: work/arch/s390/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/s390/kernel/vmlinux.lds.S
+++ work/arch/s390/kernel/vmlinux.lds.S
@@ -157,14 +157,10 @@ SECTIONS

_end = . ;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
/* Debugging sections. */
STABS_DEBUG
DWARF_DEBUG
+
+ /* Sections to be discarded */
+ DISCARDS
}
Index: work/arch/sh/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/sh/kernel/vmlinux.lds.S
+++ work/arch/sh/kernel/vmlinux.lds.S
@@ -163,17 +163,14 @@ SECTIONS
_end = . ;
}

+ STABS_DEBUG
+ DWARF_DEBUG
+
/*
* When something in the kernel is NOT compiled as a module, the
* module cleanup code and data are put into these segments. Both
* can then be thrown away, as cleanup code is never called unless
* it's a module.
*/
- /DISCARD/ : {
- *(.exitcall.exit)
- *(.discard)
- }
-
- STABS_DEBUG
- DWARF_DEBUG
+ DISCARDS
}
Index: work/arch/sparc/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/sparc/kernel/vmlinux.lds.S
+++ work/arch/sparc/kernel/vmlinux.lds.S
@@ -171,13 +171,8 @@ SECTIONS
}
_end = . ;

- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
STABS_DEBUG
DWARF_DEBUG
+
+ DISCARDS
}
Index: work/arch/x86/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/x86/kernel/vmlinux.lds.S
+++ work/arch/x86/kernel/vmlinux.lds.S
@@ -387,15 +387,12 @@ SECTIONS
_end = .;
}

- /* Sections to be discarded */
- /DISCARD/ : {
- *(.exitcall.exit)
- *(.eh_frame)
- *(.discard)
- }
-
STABS_DEBUG
DWARF_DEBUG
+
+ /* Sections to be discarded */
+ DISCARDS
+ /DISCARD/ : { *(.eh_frame) }
}

Index: work/arch/xtensa/kernel/vmlinux.lds.S
===================================================================
--- work.orig/arch/xtensa/kernel/vmlinux.lds.S
+++ work/arch/xtensa/kernel/vmlinux.lds.S
@@ -280,16 +280,6 @@ SECTIONS
*(.ResetVector.text)
}

- /* Sections to be discarded */
- /DISCARD/ :
- {
- *(.exit.literal)
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
.xt.lit : { *(.xt.lit) }
.xt.prop : { *(.xt.prop) }

@@ -322,4 +312,8 @@ SECTIONS
*(.xt.lit)
*(.gnu.linkonce.p*)
}
+
+ /* Sections to be discarded */
+ DISCARDS
+ /DISCARD/ : { *(.exit.literal) }
}
Index: work/include/asm-generic/vmlinux.lds.h
===================================================================
--- work.orig/include/asm-generic/vmlinux.lds.h
+++ work/include/asm-generic/vmlinux.lds.h
@@ -35,13 +35,10 @@
* __bss_stop = .;
* _end = .;
*
- * /DISCARD/ : {
- * EXIT_TEXT
- * EXIT_DATA
- * EXIT_CALL
- * }
* STABS_DEBUG
* DWARF_DEBUG
+ *
+ * DISCARDS // must be the last
* }
*
* [__init_begin, __init_end] is the init section that may be freed after init
@@ -629,11 +626,20 @@
#define INIT_RAM_FS
#endif

+/*
+ * Default discarded sections.
+ *
+ * Some archs want to discard exit text/data at runtime rather than
+ * link time due to cross-section references such as alt instructions,
+ * bug table, eh_frame, etc. DISCARDS must be the last of output
+ * section definitions so that such archs put those in earlier section
+ * definitions.
+ */
#define DISCARDS \
/DISCARD/ : { \
EXIT_TEXT \
EXIT_DATA \
- *(.exitcall.exit) \
+ EXIT_CALL \
*(.discard) \
}

Index: work/arch/m68k/kernel/vmlinux-std.lds
===================================================================
--- work.orig/arch/m68k/kernel/vmlinux-std.lds
+++ work/arch/m68k/kernel/vmlinux-std.lds
@@ -82,14 +82,6 @@ SECTIONS

_end = . ;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
@@ -98,4 +90,7 @@ SECTIONS
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
+
+ /* Sections to be discarded */
+ DISCARDS
}
Index: work/arch/m68k/kernel/vmlinux-sun3.lds
===================================================================
--- work.orig/arch/m68k/kernel/vmlinux-sun3.lds
+++ work/arch/m68k/kernel/vmlinux-sun3.lds
@@ -77,14 +77,6 @@ __init_begin = .;

_end = . ;

- /* Sections to be discarded */
- /DISCARD/ : {
- EXIT_TEXT
- EXIT_DATA
- *(.exitcall.exit)
- *(.discard)
- }
-
.crap : {
/* Stabs debugging sections. */
*(.stab)
@@ -97,4 +89,6 @@ __init_begin = .;
*(.note)
}

+ /* Sections to be discarded */
+ DISCARDS
}
Index: work/arch/um/include/asm/common.lds.S
===================================================================
--- work.orig/arch/um/include/asm/common.lds.S
+++ work/arch/um/include/asm/common.lds.S
@@ -123,8 +123,3 @@
__initramfs_end = .;
}

- /* Sections to be discarded */
- /DISCARD/ : {
- *(.exitcall.exit)
- }
-
Index: work/arch/um/kernel/dyn.lds.S
===================================================================
--- work.orig/arch/um/kernel/dyn.lds.S
+++ work/arch/um/kernel/dyn.lds.S
@@ -157,5 +157,5 @@ SECTIONS

DWARF_DEBUG

- /DISCARD/ : { *(.discard) }
+ DISCARDS
}
Index: work/arch/um/kernel/uml.lds.S
===================================================================
--- work.orig/arch/um/kernel/uml.lds.S
+++ work/arch/um/kernel/uml.lds.S
@@ -101,5 +101,5 @@ SECTIONS

DWARF_DEBUG

- /DISCARD/ : { *(.discard) }
+ DISCARDS
}
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Next message: Paul Mundt: "Re: [PATCH] U300 sched_clock implementation"
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In reply to: Tejun Heo: "[PATCH percpu 1/2] microblaze: include EXIT_TEXT to _stext"
Next in thread: Michal Simek: "Re: [PATCH percpu 1/2] microblaze: include EXIT_TEXT to _stext"
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