linker script: unify usage of discard definition
Subsystems (15)
RFC PATCH 1/1 linker script: unify usage of discard definition
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.
On x86-64 which explicitly includes EXIT_TEXT, this produces identical output as before and all but one archs included directives (include or discard) for all default discarded sections, so this patch shouldn't cause any behavior difference.
The only problem case is microblaze, which didn't explicitly included EXIT_TEXT and DATA but didn't discard them either leaving ld to create identically names output sections for them. This patch will make the end result different by throwing away exit text and data. It looks like the ommission was accidental and throwing away is the right thing to do, but I won't push it till someone who knows microblaze confirms it.
This patch is on top of the current percpu#for-next.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-next
Thanks.
NOT_SIGNED_OFF_YET
Cc: [email protected]
Cc: Michal Simek <[email protected]>
Cc: [email protected]
Cc: Sam Ravnborg <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Tony Luck <[email protected]>
--- 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 | 22 +++++++++------------- 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 | 14 ++++++++------ 25 files changed, 77 insertions(+), 159 deletions(-)
arch/alpha/kernel/vmlinux.lds.S +2 -8
@@ -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 }
arch/avr32/kernel/vmlinux.lds.S +3 -7
@@ -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 }
arch/blackfin/kernel/vmlinux.lds.S +1 -5
@@ -277,9 +277,5 @@ SECTIONS DWARF_DEBUG - /DISCARD/ : - { - *(.exitcall.exit) - *(.discard) - } + DISCARDS }
arch/cris/kernel/vmlinux.lds.S +2 -8
@@ -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 }
arch/frv/kernel/vmlinux.lds.S +1 -1
@@ -178,7 +178,7 @@ SECTIONS .comment 0 : { *(.comment) } - /DISCARD/ : { *(.discard) } + DISCARDS } __kernel_image_size_no_bss = __bss_start - __kernel_image_start;
arch/h8300/kernel/vmlinux.lds.S +2 -4
@@ -152,10 +152,6 @@ SECTIONS __end = . ; __ramstart = .; } - /DISCARD/ : { - *(.exitcall.exit) - *(.discard) - } .romfs : { *(.romfs*)
@@ -166,4 +162,6 @@ SECTIONS COMMAND_START = . - 0x200 ; __ramend = . ; } + + DISCARDS }
arch/ia64/kernel/vmlinux.lds.S +9 -13
@@ -24,16 +24,6 @@ PHDRS { } SECTIONS { - /* Sections to be discarded */ - /DISCARD/ : { - EXIT_TEXT - EXIT_DATA - *(.exitcall.exit) - *(.discard) - *(.IA_64.unwind.exit.text) - *(.IA_64.unwind_info.exit.text) - } - v = PAGE_OFFSET; /* this symbol is here to make debugging easier... */ phys_start = _start - LOAD_OFFSET;
@@ -317,7 +307,13 @@ 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) } + + /* Sections to be discarded */ + DISCARDS + /DISCARD/ : { + *(.IA_64.unwind.exit.text) + *(.IA_64.unwind_info.exit.text) + *(.comment) + *(.note) + } }
arch/m32r/kernel/vmlinux.lds.S +3 -8
@@ -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 }
arch/m68knommu/kernel/vmlinux.lds.S +1 -7
@@ -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 }
arch/microblaze/kernel/vmlinux.lds.S +1 -1
@@ -163,5 +163,5 @@ SECTIONS { . = ALIGN(4096); _end = .; - /DISCARD/ : { *(.discard) } + DISCARDS }
arch/mips/kernel/vmlinux.lds.S +10 -12
@@ -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) + } }
arch/mn10300/kernel/vmlinux.lds.S +3 -6
@@ -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 }
arch/parisc/kernel/vmlinux.lds.S +4 -5
@@ -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) } }
arch/powerpc/kernel/vmlinux.lds.S +3 -7
@@ -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 }
arch/s390/kernel/vmlinux.lds.S +3 -7
@@ -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 }
arch/sh/kernel/vmlinux.lds.S +4 -7
@@ -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 }
arch/sparc/kernel/vmlinux.lds.S +2 -7
@@ -171,13 +171,8 @@ SECTIONS } _end = . ; - /DISCARD/ : { - EXIT_TEXT - EXIT_DATA - *(.exitcall.exit) - *(.discard) - } - STABS_DEBUG DWARF_DEBUG + + DISCARDS }
arch/x86/kernel/vmlinux.lds.S +4 -7
@@ -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) } }
arch/xtensa/kernel/vmlinux.lds.S +4 -10
@@ -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) } }
include/asm-generic/vmlinux.lds.h +8 -6
@@ -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 +626,16 @@#define INIT_RAM_FS #endif +/* +* DISCARDS must be the last and archs which want some of the default +* discarded sections in the kernel image can do so by putting them in +* earlier section definition. +*/ #define DISCARDS \ /DISCARD/ : { \ EXIT_TEXT \ EXIT_DATA \ - *(.exitcall.exit) \ + EXIT_CALL \ *(.discard) \ }
arch/m68k/kernel/vmlinux-std.lds +3 -8
@@ -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 }
arch/m68k/kernel/vmlinux-sun3.lds +2 -8
@@ -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 }
arch/um/include/asm/common.lds.S +0 -5
@@ -123,8 +123,3 @@ __initramfs_end = .; } - /* Sections to be discarded */ - /DISCARD/ : { - *(.exitcall.exit) - } -
arch/um/kernel/dyn.lds.S +1 -1
@@ -157,5 +157,5 @@ SECTIONS DWARF_DEBUG - /DISCARD/ : { *(.discard) } + DISCARDS }
arch/um/kernel/uml.lds.S +1 -1
@@ -101,5 +101,5 @@ SECTIONS DWARF_DEBUG - /DISCARD/ : { *(.discard) } + DISCARDS }
linux-next submission requirements (Was: [RFC PATCH] linker script: unify usage of discard definition)
Hi Tejun,
[This is not aimed just at you ... this patch just gave me an opportunity to point this out again.]
Quoted 8 lines · On Sat, 04 Jul 2009 08:37:28 +0900 Tejun Heo <[email protected]> wrote:
This patch is on top of the current percpu#for-next.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.gitfor-nextThanks.
NOT_SIGNED_OFF_YET
Well, given no SOB and that this is a RFC patch, it should *not* be in a branch that is pulled into linux-next.
This is what I send to any maintainer that submits a tree for linux-next inclusion (and before anyone else points it out: this was not true early on):
"all patches/commits in the tree/series must have been:
posted to a relevant mailing list
reviewed
unit tested
destined for the next merge window (or the current release)
*before* they are included. The linux-next tree is for integration testing and to lower the impact of conflicts between subsystems in the next merge window.
Basically, this should be just what you would send to Linus (or ask him to fetch). It is allowed to be rebased if you deem it necessary."
Signature · 3 lines
Cheers, Stephen Rothwell [email protected] http://www.canb.auug.org.au/~sfr/
Re: linux-next submission requirements (Was: [RFC PATCH] linker script: unify usage of discard definition)
Hello,
Quoted 8 lines · Stephen Rothwell
Hi Tejun,
[This is not aimed just at you ... this patch just gave me an opportunity to point this out again.]
Quoted 2 lines · On Sat, 04 Jul 2009 08:37:28 +0900 Tejun Heo <[email protected]> wrote:
This patch is on top of the current percpu#for-next.
Quoted 8 lines
Quoted 5 lines
git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.gitfor-nextThanks.
NOT_SIGNED_OFF_YETWell, given no SOB and that this is a RFC patch, it should *not* be in a branch that is pulled into linux-next.
It's not _in_ the branch. It's on _top_ of the branch.
Thanks.
Signature · 1 line
tejun
Re: linux-next submission requirements (Was: [RFC PATCH] linker script: unify usage of discard definition)
Hi Tejun,
Quoted 7 lines · On Sat, 04 Jul 2009 12:18:02 +0900 Tejun Heo <[email protected]> wrote:
Quoted 3 lines · Stephen Rothwell
[This is not aimed just at you ... this patch just gave me an opportunity to point this out again.]
It's not _in_ the branch. It's on _top_ of the branch.
Ah, sorry, I read that as "at the top of". In that case, this is not aimed at you at all :-)
Signature · 3 lines
Cheers, Stephen Rothwell [email protected] http://www.canb.auug.org.au/~sfr/
Re: linux-next submission requirements (Was: [RFC PATCH] linker script: unify usage of discard definition)
Quoted 10 lines · Stephen Rothwell
Hi Tejun,
Quoted 4 lines · On Sat, 04 Jul 2009 12:18:02 +0900 Tejun Heo <[email protected]> wrote:
Quoted 2 lines · Stephen Rothwell
[This is not aimed just at you ... this patch just gave me an opportunity to point this out again.]
It's not _in_ the branch. It's on _top_ of the branch.
Ah, sorry, I read that as "at the top of". In that case, this is not aimed at you at all :-)
:-)
Signature · 1 line
tejun
Quoted 5 lines · Tejun Heo
+/*
+ * DISCARDS must be the last and archs which want some of the default
+ * discarded sections in the kernel image can do so by putting them in
+ * earlier section definition.
+ */
Quoted 8 lines
#define DISCARDS \
/DISCARD/ : { \
EXIT_TEXT \
EXIT_DATA \
- *(.exitcall.exit) \
+EXIT_CALL\
*(.discard) \
}
i would add to the comment that some people 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...
otherwise, looks good to me. thanks !
-mike
Paul Mundt
Acked-byQuoted 7 lines · Mike Frysinger
Quoted 5 lines · Tejun Heo
+/*
+ * DISCARDS must be the last and archs which want some of the default
+ * discarded sections in the kernel image can do so by putting them in
+ * earlier section definition.
+ */
Quoted 7 lines
i would add to the comment that some people 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...otherwise, looks good to me. thanks !
Acked-by Mike Frysinger <[email protected]>
Agreed, as this was a source of confusion initially it is certainly worth documenting the next time someone is scratching their head thinking about the variations ;-)
Michal Simek
maintainerQuoted 15 lines · Tejun Heo
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.
On x86-64 which explicitly includes
EXIT_TEXT, this produces identical output as before and all but one archs included directives (include or discard) for all default discarded sections, so this patch shouldn't cause any behavior difference.
Quoted 7 lines
The only problem case is microblaze, which didn't explicitly included
EXIT_TEXTand DATA but didn't discard them either leaving ld to create identically names output sections for them. This patch will make the end result different by throwing away exit text and data. It looks like the ommission was accidental and throwing away is the right thing to do, but I won't push it till someone who knows microblaze confirms it.
As you expected noMMU Microblaze kernel has some problems with that patch. (MMU version is fine) I'll take a look at it closer yesterday.
Thanks,
Michal
Quoted 7 lines
___________________________
microblaze-uclinux mailing list
[email protected]
Project Home Page : http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux
Mailing List Archive : http://www.itee.uq.edu.au/~listarch/microblaze-uclinux/
Signature · 2 lines
Michal Simek, Ing. (M.Eng) w: www.monstr.eu p: +42-0-721842854
Quoted 15 lines · Tejun Heo
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.
On x86-64 which explicitly includes
EXIT_TEXT, this produces identical output as before and all but one archs included directives (include or discard) for all default discarded sections, so this patch shouldn't cause any behavior difference.
Quoted 7 lines
The only problem case is microblaze, which didn't explicitly included
EXIT_TEXTand DATA but didn't discard them either leaving ld to create identically names output sections for them. This patch will make the end result different by throwing away exit text and data. It looks like the ommission was accidental and throwing away is the right thing to do, but I won't push it till someone who knows microblaze confirms it.
Please include EXIT_TEXT to .text section. EXIT_DATA can be discard. Patch is below.
Thanks,
Michal
arch/microblaze/kernel/vmlinux.lds.S +2 -2
@@ -23,8 +23,8 @@ SECTIONS { _stext = . ; *(.text .text.*) *(.fixup) - - *(.exitcall.exit) + EXIT_TEXT + EXIT_CALL SCHED_TEXT LOCK_TEXT KPROBES_TEXT
Signature · 2 lines
Michal Simek, Ing. (M.Eng) w: www.monstr.eu p: +42-0-721842854