missing .data.shared_align placement in vmlinux

missing .data.shared_align placement in vmlinux

[Mike Frysinger]

am i missing something or does the .data.shared_align section lack
definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?

with the recent change "net: remove time limit in process_backlog()",
the softnet_data variable changed from "DEFINE_PER_CPU()" to
"DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
the .data.shared_align section.  i'm not saying this patch is wrong,
just that is what caused me to notice this larger problem.  no one
else in the kernel is using this aligned macro variant, so i imagine
that's why no one has noticed yet.

since .data.shared_align isnt declared in any vmlinux files that i can
see, the linker just places it last.  this "just works" for most
people, but when building a ROM kernel on Blackfin systems, it causes
section overlap errors:
bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
00000000202e48b7] overlaps section .data.shared_aligned
[00000000202e06b8 -> 00000000202e0723]
i imagine other arches which support the ROM config option and thus do
funky placement would see similar issues ...

on x86, it is stuck in a dedicated section:
  [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
0303a8 00  WA  0   0 4096
  [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
0000c8 00  WA  0   0 64

the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
fix, so i leave it up to someone else ;)
-mike

Re: missing .data.shared_align placement in vmlinux

[Sam Ravnborg]

On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
> am i missing something or does the .data.shared_align section lack
> definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?
> 
> with the recent change "net: remove time limit in process_backlog()",
> the softnet_data variable changed from "DEFINE_PER_CPU()" to
> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
> the .data.shared_align section.  i'm not saying this patch is wrong,
> just that is what caused me to notice this larger problem.  no one
> else in the kernel is using this aligned macro variant, so i imagine
> that's why no one has noticed yet.
> 
> since .data.shared_align isnt declared in any vmlinux files that i can
> see, the linker just places it last.  this "just works" for most
> people, but when building a ROM kernel on Blackfin systems, it causes
> section overlap errors:
> bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
> 00000000202e48b7] overlaps section .data.shared_aligned
> [00000000202e06b8 -> 00000000202e0723]
> i imagine other arches which support the ROM config option and thus do
> funky placement would see similar issues ...
> 
> on x86, it is stuck in a dedicated section:
>   [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
> 0303a8 00  WA  0   0 4096
>   [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
> 0000c8 00  WA  0   0 64
> 
> the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
> fix, so i leave it up to someone else ;)

as there any resolution on this?
I briefly looked at it some time ago.
And it looks like a plain oversight.

But I was also a bit lost in the forest of ifdef land...

	Sam

Re: missing .data.shared_align placement in vmlinux

[Mike Frysinger]

On Wed, Aug 4, 2010 at 07:56, Sam Ravnborg wrote:
> On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
>> am i missing something or does the .data.shared_align section lack
>> definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?
>>
>> with the recent change "net: remove time limit in process_backlog()",
>> the softnet_data variable changed from "DEFINE_PER_CPU()" to
>> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
>> the .data.shared_align section.  i'm not saying this patch is wrong,
>> just that is what caused me to notice this larger problem.  no one
>> else in the kernel is using this aligned macro variant, so i imagine
>> that's why no one has noticed yet.
>>
>> since .data.shared_align isnt declared in any vmlinux files that i can
>> see, the linker just places it last.  this "just works" for most
>> people, but when building a ROM kernel on Blackfin systems, it causes
>> section overlap errors:
>> bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
>> 00000000202e48b7] overlaps section .data.shared_aligned
>> [00000000202e06b8 -> 00000000202e0723]
>> i imagine other arches which support the ROM config option and thus do
>> funky placement would see similar issues ...
>>
>> on x86, it is stuck in a dedicated section:
>>   [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
>> 0303a8 00  WA  0   0 4096
>>   [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
>> 0000c8 00  WA  0   0 64
>>
>> the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
>> fix, so i leave it up to someone else ;)
>
> as there any resolution on this?
> I briefly looked at it some time ago.
> And it looks like a plain oversight.

no, it's still broken in 2.6.35 :(
$ make ARCH=blackfin BF537-STAMP_defconfig
$ make ARCH=blackfin -s -j4
$ readelf -WS vmlinux | grep '\<data\>'
  [10] .data             PROGBITS        0018369c 17269c 012964 00  WA  0   0  4
  [11] .data..shared_aligned PROGBITS        00196000 185000 00006c 00
 WA  0   0  4
-mike

Re: missing .data.shared_align placement in vmlinux

[Sam Ravnborg]

On Wed, Aug 04, 2010 at 02:12:03PM -0400, Mike Frysinger wrote:
> On Wed, Aug 4, 2010 at 07:56, Sam Ravnborg wrote:
> > On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
> >> am i missing something or does the .data.shared_align section lack
> >> definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?
> >>
> >> with the recent change "net: remove time limit in process_backlog()",
> >> the softnet_data variable changed from "DEFINE_PER_CPU()" to
> >> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
> >> the .data.shared_align section.  i'm not saying this patch is wrong,
> >> just that is what caused me to notice this larger problem.  no one
> >> else in the kernel is using this aligned macro variant, so i imagine
> >> that's why no one has noticed yet.
> >>
> >> since .data.shared_align isnt declared in any vmlinux files that i can
> >> see, the linker just places it last.  this "just works" for most
> >> people, but when building a ROM kernel on Blackfin systems, it causes
> >> section overlap errors:
> >> bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
> >> 00000000202e48b7] overlaps section .data.shared_aligned
> >> [00000000202e06b8 -> 00000000202e0723]
> >> i imagine other arches which support the ROM config option and thus do
> >> funky placement would see similar issues ...
> >>
> >> on x86, it is stuck in a dedicated section:
> >>   [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
> >> 0303a8 00  WA  0   0 4096
> >>   [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
> >> 0000c8 00  WA  0   0 64
> >>
> >> the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
> >> fix, so i leave it up to someone else ;)
> >
> > as there any resolution on this?
> > I briefly looked at it some time ago.
> > And it looks like a plain oversight.
> 
> no, it's still broken in 2.6.35 :(
> $ make ARCH=blackfin BF537-STAMP_defconfig
> $ make ARCH=blackfin -s -j4
> $ readelf -WS vmlinux | grep '\<data\>'
>   [10] .data             PROGBITS        0018369c 17269c 012964 00  WA  0   0  4
>   [11] .data..shared_aligned PROGBITS        00196000 185000 00006c 00
>  WA  0   0  4

Following simple patch should deal with it.
Jeremy - you introduced this in ("x86/i386: Put aligned
stack-canary in percpu shared_aligned section")
53f824520b6d84ca5b4a8fd71addc91dbf64357e

Does the following simple fix look correct to you?

	Sam

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 030a954..e87260f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -150,6 +150,7 @@
 #define DATA_DATA							\
 	*(.data)							\
 	*(.ref.data)							\
+	*(.data..shared_aligned) /* percpu related */			\
 	DEV_KEEP(init.data)						\
 	DEV_KEEP(exit.data)						\
 	CPU_KEEP(init.data)						\

Re: missing .data.shared_align placement in vmlinux

[Sam Ravnborg]

[Resend - this time with Jeremy included in To: ]

Jeremy - you introduced this in ("x86/i386: Put aligned
stack-canary in percpu shared_aligned section")
53f824520b6d84ca5b4a8fd71addc91dbf64357e

Does the following simple fix look correct to you?
[See below]

	Sam

> 
On Wed, Aug 04, 2010 at 10:28:06PM +0200, Sam Ravnborg wrote:
> On Wed, Aug 04, 2010 at 02:12:03PM -0400, Mike Frysinger wrote:
> > On Wed, Aug 4, 2010 at 07:56, Sam Ravnborg wrote:
> > > On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
> > >> am i missing something or does the .data.shared_align section lack
> > >> definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?
> > >>
> > >> with the recent change "net: remove time limit in process_backlog()",
> > >> the softnet_data variable changed from "DEFINE_PER_CPU()" to
> > >> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
> > >> the .data.shared_align section.  i'm not saying this patch is wrong,
> > >> just that is what caused me to notice this larger problem.  no one
> > >> else in the kernel is using this aligned macro variant, so i imagine
> > >> that's why no one has noticed yet.
> > >>
> > >> since .data.shared_align isnt declared in any vmlinux files that i can
> > >> see, the linker just places it last.  this "just works" for most
> > >> people, but when building a ROM kernel on Blackfin systems, it causes
> > >> section overlap errors:
> > >> bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
> > >> 00000000202e48b7] overlaps section .data.shared_aligned
> > >> [00000000202e06b8 -> 00000000202e0723]
> > >> i imagine other arches which support the ROM config option and thus do
> > >> funky placement would see similar issues ...
> > >>
> > >> on x86, it is stuck in a dedicated section:
> > >>   [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
> > >> 0303a8 00  WA  0   0 4096
> > >>   [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
> > >> 0000c8 00  WA  0   0 64
> > >>
> > >> the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
> > >> fix, so i leave it up to someone else ;)
> > >
> > > as there any resolution on this?
> > > I briefly looked at it some time ago.
> > > And it looks like a plain oversight.
> > 
> > no, it's still broken in 2.6.35 :(
> > $ make ARCH=blackfin BF537-STAMP_defconfig
> > $ make ARCH=blackfin -s -j4
> > $ readelf -WS vmlinux | grep '\<data\>'
> >   [10] .data             PROGBITS        0018369c 17269c 012964 00  WA  0   0  4
> >   [11] .data..shared_aligned PROGBITS        00196000 185000 00006c 00
> >  WA  0   0  4
> 

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 030a954..e87260f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -150,6 +150,7 @@
 #define DATA_DATA							\
 	*(.data)							\
 	*(.ref.data)							\
+	*(.data..shared_aligned) /* percpu related */			\
 	DEV_KEEP(init.data)						\
 	DEV_KEEP(exit.data)						\
 	CPU_KEEP(init.data)						\

Re: missing .data.shared_align placement in vmlinux

[Jeremy Fitzhardinge]

  On 08/04/2010 01:40 PM, Sam Ravnborg wrote:
> [Resend - this time with Jeremy included in To: ]
>
> Jeremy - you introduced this in ("x86/i386: Put aligned
> stack-canary in percpu shared_aligned section")
> 53f824520b6d84ca5b4a8fd71addc91dbf64357e
>
> Does the following simple fix look correct to you?
> [See below]
>
> 	Sam
>
> On Wed, Aug 04, 2010 at 10:28:06PM +0200, Sam Ravnborg wrote:
>> On Wed, Aug 04, 2010 at 02:12:03PM -0400, Mike Frysinger wrote:
>>> On Wed, Aug 4, 2010 at 07:56, Sam Ravnborg wrote:
>>>> On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
>>>>> am i missing something or does the .data.shared_align section lack
>>>>> definition in vmlinux.lds.h and all arch vmlinux.lds.S files ?
>>>>>
>>>>> with the recent change "net: remove time limit in process_backlog()",
>>>>> the softnet_data variable changed from "DEFINE_PER_CPU()" to
>>>>> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
>>>>> the .data.shared_align section.  i'm not saying this patch is wrong,
>>>>> just that is what caused me to notice this larger problem.  no one
>>>>> else in the kernel is using this aligned macro variant, so i imagine
>>>>> that's why no one has noticed yet.

That's a bit odd and embarrassing...  I guess the stack_canary stuff is 
only visible when using CONFIG_CC_STACKPROTECTOR.

>>>>> since .data.shared_align isnt declared in any vmlinux files that i can
>>>>> see, the linker just places it last.  this "just works" for most
>>>>> people, but when building a ROM kernel on Blackfin systems, it causes
>>>>> section overlap errors:
>>>>> bfin-uclinux-ld.real: section .init.data [00000000202e06b8 ->
>>>>> 00000000202e48b7] overlaps section .data.shared_aligned
>>>>> [00000000202e06b8 ->  00000000202e0723]
>>>>> i imagine other arches which support the ROM config option and thus do
>>>>> funky placement would see similar issues ...
>>>>>
>>>>> on x86, it is stuck in a dedicated section:
>>>>>    [ 8] .data             PROGBITS        ffffffff810ec000 2ec000
>>>>> 0303a8 00  WA  0   0 4096
>>>>>    [ 9] .data.shared_alig PROGBITS        ffffffff8111c3c0 31c3c0
>>>>> 0000c8 00  WA  0   0 64
>>>>>
>>>>> the ifdef forest in asm-generic/percpu.h is beyond a quick glance&
>>>>> fix, so i leave it up to someone else ;)
>>>> as there any resolution on this?
>>>> I briefly looked at it some time ago.
>>>> And it looks like a plain oversight.
>>> no, it's still broken in 2.6.35 :(
>>> $ make ARCH=blackfin BF537-STAMP_defconfig
>>> $ make ARCH=blackfin -s -j4
>>> $ readelf -WS vmlinux | grep '\<data\>'
>>>    [10] .data             PROGBITS        0018369c 17269c 012964 00  WA  0   0  4
>>>    [11] .data..shared_aligned PROGBITS        00196000 185000 00006c 00
>>>   WA  0   0  4
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 030a954..e87260f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -150,6 +150,7 @@
>   #define DATA_DATA							\
>   	*(.data)							\
>   	*(.ref.data)							\
> +	*(.data..shared_aligned) /* percpu related */			\

Typo?  Shouldn't that be ".data.shared_aligned"?  Or where does the '..' 
come from?

     J

Re: missing .data.shared_align placement in vmlinux

[Mike Frysinger]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=UTF-8, Size: 1126 bytes --]

On Thu, Aug 5, 2010 at 01:14, Jeremy Fitzhardinge wrote:
>  On 08/04/2010 01:40 PM, Sam Ravnborg wrote:
>> --- a/include/asm-generic/vmlinux.lds.h
>> +++ b/include/asm-generic/vmlinux.lds.h
>> @@ -150,6 +150,7 @@
>>  #define DATA_DATA                                                     \
>>        *(.data)                                                        \
>>        *(.ref.data)                                                    \
>> +       *(.data..shared_aligned) /* percpu related */                   \
>
> Typo?  Shouldn't that be ".data.shared_aligned"?  Or where does the '..'
> come from?

include/asm-generic/percpu.h:#define PER_CPU_SHARED_ALIGNED_SECTION
"..shared_aligned"
include/asm-generic/percpu.h:#define PER_CPU_ALIGNED_SECTION "..shared_aligned"
include/asm-generic/percpu.h:#define PER_CPU_ALIGNED_SECTION "..shared_aligned"
-mike
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Re: missing .data.shared_align placement in vmlinux

[Mike Frysinger]

On Wed, Aug 4, 2010 at 16:40, Sam Ravnborg wrote:
> [Resend - this time with Jeremy included in To: ]
>
> Jeremy - you introduced this in ("x86/i386: Put aligned
> stack-canary in percpu shared_aligned section")
> 53f824520b6d84ca5b4a8fd71addc91dbf64357e

can we get this merged for 2.6.36 ?
-mike

[PATCH] vmlinux.lds.h: gather .data..shared_aligned sections in DATA_DATA

[Mike Frysinger]

With the recent change "net: remove time limit in process_backlog()",
the softnet_data variable changed from "DEFINE_PER_CPU()" to
"DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
the .data.shared_align section.  I'm not saying this patch is wrong,
just that is what caused me to notice this larger problem.  No one
else in the kernel is using this aligned macro variant, so I imagine
that's why no one has noticed yet.

Since .data.shared_align isnt declared in any vmlinux files that I can
see, the linker just places it last.  This "just works" for most
people, but when building a ROM kernel on Blackfin systems, it causes
section overlap errors:
bfin-uclinux-ld.real:
	section .init.data [00000000202e06b8 -> 00000000202e48b7] overlaps
	section .data.shared_aligned [00000000202e06b8 -> 00000000202e0723]
I imagine other arches which support the ROM config option and thus do
funky placement would see similar issues ...

On x86, it is stuck in a dedicated section at the end:
 [8] .data             PROGBITS ffffffff810ec000 2ec0000303a8 00 WA 0 0 4096
 [9] .data.shared_alig PROGBITS ffffffff8111c3c0 31c3c00000c8 00 WA 0 0 64

So mark sure we include this section in the DATA_DATA macro so that
it is placed in the right location.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
note: this was reported back in May, patch posted in Aug, and no feedback since

 include/asm-generic/vmlinux.lds.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 7657a3b..75b6b58 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -150,6 +150,7 @@
 #define DATA_DATA							\
 	*(.data)							\
 	*(.ref.data)							\
+	*(.data..shared_aligned) /* percpu related */			\
 	DEV_KEEP(init.data)						\
 	DEV_KEEP(exit.data)						\
 	CPU_KEEP(init.data)						\
-- 
1.7.3.1

Re: [PATCH] vmlinux.lds.h: gather .data..shared_aligned sections in DATA_DATA

[Mike Frysinger]

Sam: i'm not trying to steal credit here ... if you want me to resend
with you as author + sob, lemme know.  i'd just like this issue fixed
already since 2.6.35 shipped with this broken setup.
-mike

Re: [PATCH] vmlinux.lds.h: gather .data..shared_aligned sections in DATA_DATA

[Sam Ravnborg]

On Mon, Oct 18, 2010 at 02:30:37AM -0400, Mike Frysinger wrote:
> Sam: i'm not trying to steal credit here ... if you want me to resend
> with you as author + sob, lemme know.  i'd just like this issue fixed
> already since 2.6.35 shipped with this broken setup.

IIRC you suggested the fix in the first place anyway.
Let's get it fixed.

	Sam