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From: Tony Luck <tony.luck@gmail.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Alan Jenkins <alan-jenkins@tuffmail.co.uk>,
	Sam Ravnborg <sam@ravnborg.org>,
	Mike Frysinger <vapier.adi@gmail.com>,
	greg@kroah.com, linux-kbuild@vger.kernel.org,
	carmelo73@gmail.com, linux-kernel@vger.kernel.org,
	achiang@hp.com, kyle@mcmartin.ca, deller@gmx.de,
	jejb@parisc-linux.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	paulus@samba.org
Subject: Re: [PATCH 05/10] kbuild: sort the list of symbols exported by the  kernel (__ksymtab)
Date: Fri, 20 Nov 2009 14:20:01 -0800	[thread overview]
Message-ID: <12c511ca0911201420i5f2d4751m25ae5288b69dbabb@mail.gmail.com> (raw)
In-Reply-To: <200911091347.57286.rusty@rustcorp.com.au>

The sorted ksymtab breaks ia64 (and possibly ppc64 and
parisc too).

Alex Chiang did the bisect to find this change as
the cause of the breakage.  The problem is that ia64
expects that the first item in each ksymtab entry to be
a function pointer.  The code in modpost that creates
.tmp_exports-asm.S doesn't know about types of exported
objects, so it uses __EXPORT_SYMBOL from linux/mod_export.h
for everything. This results in

        PTR SYM(sym);
        PTR SYM(__kstrtab_##sym);

which the preprocessor expands to entries like:

        .long ____pagevec_lru_add
        .long __kstrtab____pagevec_lru_add

which puts the address of the first instruction of the
function into the table, rather than the address of a
function pointer (which on ia64 is a two element data
object containing the code address and the global data
pointer).

The syntax you need for this* is:

        .long @fptr(____pagevec_lru_add)
        .long __kstrtab____pagevec_lru_add

Note that you must only use the @fptr(name) syntax for
function exports. Exported data items just need an address.

-Tony

* On ia64 ... powerpc and parisc might need something else.

WARNING: multiple messages have this Message-ID
From: Tony Luck <tony.luck@gmail.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Alan Jenkins <alan-jenkins@tuffmail.co.uk>,
	Sam Ravnborg <sam@ravnborg.org>,
	Mike Frysinger <vapier.adi@gmail.com>,
	greg@kroah.com, linux-kbuild@vger.kernel.org,
	carmelo73@gmail.com, linux-kernel@vger.kernel.org,
	achiang@hp.com, kyle@mcmartin.ca, deller@gmx.de,
	jejb@parisc-linux.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	paulus@samba.org
Subject: Re: [PATCH 05/10] kbuild: sort the list of symbols exported by the kernel (__ksymtab)
Date: Fri, 20 Nov 2009 14:20:01 -0800	[thread overview]
Message-ID: <12c511ca0911201420i5f2d4751m25ae5288b69dbabb@mail.gmail.com> (raw)
In-Reply-To: <200911091347.57286.rusty@rustcorp.com.au>

The sorted ksymtab breaks ia64 (and possibly ppc64 and
parisc too).

Alex Chiang did the bisect to find this change as
the cause of the breakage.  The problem is that ia64
expects that the first item in each ksymtab entry to be
a function pointer.  The code in modpost that creates
.tmp_exports-asm.S doesn't know about types of exported
objects, so it uses __EXPORT_SYMBOL from linux/mod_export.h
for everything. This results in

        PTR SYM(sym);
        PTR SYM(__kstrtab_##sym);

which the preprocessor expands to entries like:

        .long ____pagevec_lru_add
        .long __kstrtab____pagevec_lru_add

which puts the address of the first instruction of the
function into the table, rather than the address of a
function pointer (which on ia64 is a two element data
object containing the code address and the global data
pointer).

The syntax you need for this* is:

        .long @fptr(____pagevec_lru_add)
        .long __kstrtab____pagevec_lru_add

Note that you must only use the @fptr(name) syntax for
function exports. Exported data items just need an address.

-Tony

* On ia64 ... powerpc and parisc might need something else.

  reply	other threads:[~2009-11-20 22:19 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-11-02 16:52 Fast LKM symbol resolution Alan Jenkins
2009-11-03  3:55 ` Greg KH
2009-11-03 10:06 ` [PATCH 0/10] module: Speed up symbol resolution during module loading (using binary search) Alan Jenkins
2009-11-03 15:58   ` Greg KH
2009-11-05 12:17     ` Rusty Russell
2009-11-03 10:06 ` [PATCH 01/10] ARM: use unified discard definition in linker script Alan Jenkins
2009-11-03 10:06 ` [PATCH 02/10] ARM: unexport symbols used to implement floating point emulation Alan Jenkins
2009-11-03 10:06 ` [PATCH 03/10] module: extract __EXPORT_SYMBOL from module.h into mod_export.h Alan Jenkins
2009-11-03 10:06 ` [PATCH 04/10] module: make MODULE_SYMBOL_PREFIX into a CONFIG option Alan Jenkins
2009-11-03 10:19   ` Mike Frysinger
2009-11-03 10:19     ` Mike Frysinger
2009-11-03 12:16     ` Alan Jenkins
2009-11-03 12:30       ` Mike Frysinger
2009-11-03 12:30         ` Mike Frysinger
2009-11-03 13:29         ` Paul Mundt
2009-11-03 13:39           ` Mike Frysinger
2009-11-03 13:39             ` Mike Frysinger
2009-11-03 13:46             ` Paul Mundt
2009-11-03 13:58               ` Mike Frysinger
2009-11-03 13:58                 ` Mike Frysinger
2009-11-03 14:07                 ` Paul Mundt
2009-11-03 10:06 ` [PATCH 05/10] kbuild: sort the list of symbols exported by the kernel (__ksymtab) Alan Jenkins
2009-11-04  8:19   ` Rusty Russell
2009-11-04 10:00     ` Alan Jenkins
2009-11-04 11:12       ` Mike Frysinger
2009-11-04 11:12         ` Mike Frysinger
2009-11-04 17:19       ` Sam Ravnborg
2009-11-05 14:24         ` Alan Jenkins
2009-11-05 16:17           ` Mike Frysinger
2009-11-05 16:17             ` Mike Frysinger
2009-11-09  3:17           ` Rusty Russell
2009-11-20 22:20             ` Tony Luck [this message]
2009-11-20 22:20               ` Tony Luck
2009-11-21  0:02               ` Alan Jenkins
2009-11-23 19:53                 ` Alex Chiang
2009-11-23 22:44                   ` Alan Jenkins
2009-11-24  0:57                   ` Rusty Russell
2009-11-24  5:39                     ` James Bottomley
2009-11-24  9:28                       ` Alan Jenkins
2009-11-24 22:43                         ` James Bottomley
2009-11-25  9:15                           ` Alan Jenkins
2009-11-25 15:08                             ` James Bottomley
2009-11-25 17:01                               ` Alan Jenkins
2009-11-27 11:03                               ` Rusty Russell
2009-11-26  0:40   ` Andrew Morton
2009-11-26 17:14     ` Alan Jenkins
2009-11-03 10:06 ` [PATCH 06/10] module: refactor symbol tables and try to reduce code size of each_symbol() Alan Jenkins
2009-11-04  8:28   ` Rusty Russell
2009-11-04  9:45     ` Alan Jenkins
2009-11-03 10:06 ` [PATCH 07/10] lib: Add generic binary search function to the kernel Alan Jenkins
2009-11-03 10:06 ` [PATCH 08/10] lib: bsearch - remove redundant special case for arrays of size 0 Alan Jenkins
2009-11-03 10:06 ` [PATCH 09/10] module: speed up find_symbol() using binary search on the builtin symbol tables Alan Jenkins
2009-11-04  8:31   ` Rusty Russell
2009-11-03 10:06 ` [PATCH 10/10] module: fix is_exported() to return true for all types of exports Alan Jenkins
2009-11-04  8:32   ` Rusty Russell
2009-11-06  5:37 ` Fast LKM symbol resolution Carmelo Amoroso
2009-11-07 20:59 [PATCH 0/10] module: Speed up symbol resolution during module loading (using binary search) Alan Jenkins
2009-11-07 21:03 ` [PATCH 05/10] kbuild: sort the list of symbols exported by the kernel (__ksymtab) Alan Jenkins

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