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Re: history of extratext sections?

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[view original message]
From: Robin Getz <rgetz@...>
To: <paulus@...>
Cc: <linux-kernel@...>, Andrew Morton <akpm@...>
Subject: history of extratext sections?
Date: Wednesday, October 24, 2007 - 8:36 am

Paul:


I noticed that when passing a zero address to kallsyms_lookup(), the kernel

thought it was a valid kernel address, even if it was not for the specific

architecture I was running things on.


This was because is_kernel_extratext() was checking against labels that don't

exist on many archs. Since PPC is the only kernel which defines _extra_text,

(which doesn't seem to be used anymore?) there are three options:

 - make the check dependant on PPC

 - make the check dependant on extratext being populated

 - remove _extra_text support from:

    linux-2.6.x/arch/ppc/kernel/vmlinux.lds.S

    linux-2.6.x/include/asm-generic/sections.h

    linux-2.6.x/kernel/kallsyms.c

    linux-2.6.x/scripts/kallsyms.c


Since I don't know the history on that label I thought I would ask (since you

seem to be the only arch using it) before I sent a patch.


-Robin


Because #1 & #2 are trivial, here is what I was thinking:


 - make the check dependant on PPC

===================================================================

--- linux-2.6.x/kernel/kallsyms.c       (revision 3760)

+++ linux-2.6.x/kernel/kallsyms.c       (working copy)

@@ -51,7 +51,8 @@

 static inline int is_kernel_extratext(unsigned long addr)

 {

+ #ifdef CONFIG_PPC

        if (addr >= (unsigned long)_sextratext

            && addr <= (unsigned long)_eextratext)

                return 1;

+ #endif

        return 0;

 }


OR 


 - make the check dependant on extratext being populated

===================================================================

--- linux-2.6.x/kernel/kallsyms.c       (revision 3760)

+++ linux-2.6.x/kernel/kallsyms.c       (working copy)

@@ -51,7 +51,8 @@

 static inline int is_kernel_extratext(unsigned long addr)

 {

        if (addr >= (unsigned long)_sextratext

-           && addr <= (unsigned long)_eextratext)

+           && addr <= (unsigned long)_eextratext

+           && _sextratext && _eextratext)

                return 1;

        ret...
[ message continues ]
[view original message]
From: Robin Getz <rgetz@...>
To: David Woodhouse <dwmw2@...>, Jon Loeliger <jdl@...>
Cc: <paulus@...>, <linux-kernel@...>
Subject: Re: history of extratext sections?
Date: Friday, October 26, 2007 - 5:57 am

OK, it looks like:


David Woodhouse added this functionality 5 May 2005:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commi...


and then Jon Loeliger removed everything in this section 17 Sep 2005

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commi...


David/Jon:


Is this section still used on PPC, or can the entire support for extratext be removed?


Thanks

-
[view original message]
From: David Woodhouse <dwmw2@...>
To: Robin Getz <rgetz@...>
Cc: Jon Loeliger <jdl@...>, <paulus@...>, <linux-kernel@...>
Subject: Re: history of extratext sections?
Date: Friday, October 26, 2007 - 10:31 am

I think it can die.


--

dwmw2


-
[view original message]
From: Jon Loeliger <jdl@...>
To: David Woodhouse <dwmw2@...>
Cc: Robin Getz <rgetz@...>, <paulus@...>, <linux-kernel@...>
Subject: Re: history of extratext sections?
Date: Friday, October 26, 2007 - 10:40 am

Agreed.   For history, see this:


http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html


and


http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html


and


http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html


HTH,

jdl


-
[view original message]
From: Robin Getz <rgetz@...>
To: Andrew Morton <akpm@...>
Cc: Jon Loeliger <jdl@...>, David Woodhouse <dwmw2@...>, <paulus@...>, <linux-kernel@...>
Subject: [patch] remove support for un-needed _extratext section
Date: Friday, October 26, 2007 - 3:43 pm

From: Robin Getz <rgetz@blackfin.uclinux.org>


when passing a zero address to kallsyms_lookup(), the kernel thought it was a

valid kernel address, even if it is not. This is because is_ksym_addr() called

is_kernel_extratext() and checked against labels that don't exist on many

archs (which default as zero). Since PPC was the only kernel which defines

_extra_text, (in 2005), and no longer needs it, this patch removes _extra_text

support.


 arch/ppc/kernel/vmlinux.lds.S  |    5 -----

 include/asm-generic/sections.h |    2 --

 kernel/kallsyms.c              |   11 +----------

 scripts/kallsyms.c             |   12 +++---------

 4 files changed, 4 insertions(+), 26 deletions(-)


Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>

cc: David Woodhouse <dwmw2@infradead.org>

cc: Jon Loeliger <jdl@freescale.com>

cc: Paul Mackerras <paulus@samba.org>


----


For some history (provided by Jon):

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html


Index: kernel/kallsyms.c

===================================================================

--- kernel/kallsyms.c	(revision 3780)

+++ kernel/kallsyms.c	(working copy)

@@ -48,14 +48,6 @@

 	return 0;

 }


-static inline int is_kernel_extratext(unsigned long addr)

-{

-	if (addr >= (unsigned long)_sextratext

-	    && addr <= (unsigned long)_eextratext)

-		return 1;

-	return 0;

-}

-

 static inline int is_kernel_text(unsigned long addr)

 {

 	if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)

@@ -79,8 +71,7 @@

 	if (all_var)

 		return is_kernel(addr);


-	return is_kernel_text(addr) || is_kernel_inittext(addr) ||

-		is_kernel_extratext(addr);

+	return is_kernel_text(addr) || is_kernel_inittext(addr);

 }


 /* expand a compressed symbol data into the resulting uncompressed string,

Index: include/asm-ge...
[ message continues ]
[view original message]
From: Andrew Morton <akpm@...>
To: Robin Getz <rgetz@...>
Cc: <jdl@...>, <dwmw2@...>, <paulus@...>, <linux-kernel@...>
Subject: Re: [patch] remove support for un-needed _extratext section
Date: Monday, October 29, 2007 - 6:22 pm

On Fri, 26 Oct 2007 15:43:56 -0400


I hit numerous rejects here.  I am not sure which kernel you patched but I


Please prepare patches in `patch -p1' form.  This should have been


--- foo/kernel/kallsyms.c	(revision 3780)


I don't understand why this hunk is changing _einittext handling, and I

suspect this was a mistake, so I left that bit out.


I ended up with this:


From: Robin Getz <rgetz@blackfin.uclinux.org>


When passing a zero address to kallsyms_lookup(), the kernel thought it was

a valid kernel address, even if it is not.  This is because is_ksym_addr()

called is_kernel_extratext() and checked against labels that don't exist on

many archs (which default as zero).  Since PPC was the only kernel which

defines _extra_text, (in 2005), and no longer needs it, this patch removes

_extra_text support.


For some history (provided by Jon):

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html

 http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html


Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>

Cc: David Woodhouse <dwmw2@infradead.org>

Cc: Jon Loeliger <jdl@freescale.com>

Cc: Paul Mackerras <paulus@samba.org>

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Cc: Sam Ravnborg <sam@ravnborg.org>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

---


 arch/ppc/kernel/vmlinux.lds.S  |    5 -----

 include/asm-generic/sections.h |    2 --

 kernel/kallsyms.c              |   11 +----------

 scripts/kallsyms.c             |   24 ++++++++++--------------

 4 files changed, 11 insertions(+), 31 deletions(-)


diff -puN arch/ppc/kernel/vmlinux.lds.S~remove-support-for-un-needed-_extratext-section arch/ppc/kernel/vmlinux.lds.S

--- a/arch/ppc/kernel/vmlinux.lds.S~remove-support-for-un-needed-_extratext-section

+++ a/arch/ppc/kernel/vmlinux.lds.S

@@ -143,11 +143,6 @@ SECTIONS


   . = ALIGN(4096);

   __init_end = .;

...
[ message continues ]
[view original message]
From: Robin Getz <rgetz@...>
To: Andrew Morton <akpm@...>
Cc: <jdl@...>, <dwmw2@...>, <paulus@...>, <linux-kernel@...>
Subject: Re: [patch] remove support for un-needed _extratext section
Date: Monday, October 29, 2007 - 8:11 pm

I didn't think I did change the _einittext handling - just removed

_eextratext, and removed the trailing ||, and closed the parentheses for

the if statement.


-  (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||

+  (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")))


?

-
[view original message]
From: Mike Frysinger <vapier.adi@...>
To: Robin Getz <rgetz@...>
Cc: <paulus@...>, <linux-kernel@...>, Andrew Morton <akpm@...>
Subject: Re: history of extratext sections?
Date: Wednesday, October 24, 2007 - 12:19 pm

i think you'd want:

if (_sextratext && _eextratext &&

  ... everything else ...

-mike

-
Previous thread: 2.6.24-rc1 freezes on powerbook at first boot stage by Elimar Riesebieter on Wednesday, October 24, 2007 - 8:07 am. (6 messages)

Next thread: [PATCH] hash: Add explicit u32 and u64 versions of hash by Matthew Wilcox on Wednesday, October 24, 2007 - 8:46 am. (1 message)