* Re: Figuring out start and end of sections
@ 2010-04-14 6:21 Felipe Balbi
2010-04-14 6:30 ` Felipe Balbi
0 siblings, 1 reply; 8+ messages in thread
From: Felipe Balbi @ 2010-04-14 6:21 UTC (permalink / raw)
To: gcc-help; +Cc: iant
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Added back the list. Sorry for that, I had forgotten.
--
balbi
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From: Felipe Balbi <me@felipebalbi.com>
To: Ian Lance Taylor <iant@google.com>
Subject: Re: Figuring out start and end of sections
Date: Wed, 14 Apr 2010 09:17:33 +0300
Message-ID: <20100414061733.GA4285@gandalf>
Hi Ian,
I guess my mailer is fishy, didn't get your mail either
Ian Taylor <iant@google.com> writes:
>> is there any way to figure out where a section starts and ends ?
>>
>> I added a specific section to my program using
>> __attribute__((section "<section name>")) and now I want to figure out
>> where that section starts so I can iterate over it and call the
>> function
>> pointers I'm adding to it.
>>
>> Do I need a specific linker script to achieve that or does the default
>> scripts give me possibility to find that out ?
>
> If you are using the GNU linker, or gold, and you make the section
> name a valid C identifier, then the linker will automatically define
> symbols __start_SECNAME and __stop_SECNAME which you can use.
so you're saying that something if I name my section _init then I should
have __start__init and __stop__init identifiers ??
The following isn't compiling:
#include <stdio.h>
typedef int (*initcall_t)(void);
static int my_init(void)
{
printf("hello world from _init\n");
}
static initcall_t __my_initcall_my_init
__attribute__((__used__))
__attribute__((section("_initcall"))) = my_init;
int main(int argc, char *argv[])
{
initcall_t *fn;
for (fn = __start__initcall; fn <
__stop__initcall; fn++)
(void) fn();
return 0;
}
do I need to pass any particular option to gcc/ld to get that working ??
--
balbi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-14 6:21 Figuring out start and end of sections Felipe Balbi
@ 2010-04-14 6:30 ` Felipe Balbi
2010-04-14 6:47 ` Felipe Balbi
2010-04-14 6:50 ` Fabian Cenedese
0 siblings, 2 replies; 8+ messages in thread
From: Felipe Balbi @ 2010-04-14 6:30 UTC (permalink / raw)
To: Felipe Balbi; +Cc: gcc-help, iant
Hi,
On Wed, Apr 14, 2010 at 09:22:35AM +0300, Felipe Balbi wrote:
> #include <stdio.h>
>
> typedef int (*initcall_t)(void);
>
> static int my_init(void)
> {
> printf("hello world from _init\n");
> }
> static initcall_t __my_initcall_my_init
> __attribute__((__used__))
> __attribute__((section("_initcall"))) = my_init;
>
> int main(int argc, char *argv[])
> {
> initcall_t *fn;
>
> for (fn = __start__initcall; fn <
> __stop__initcall; fn++)
> (void) fn();
>
> return 0;
> }
I commented the for loop just to get the thing compiling and nm doesn't
show any __start_ symbols:
$ nm tst | grep init
080494cc d __init_array_end
080494cc d __init_array_start
08048400 T __libc_csu_init
080495d4 d __my_initcall_my_init
08048298 T _init
080483c4 t my_init
--
balbi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-14 6:30 ` Felipe Balbi
@ 2010-04-14 6:47 ` Felipe Balbi
2010-04-14 6:50 ` Fabian Cenedese
1 sibling, 0 replies; 8+ messages in thread
From: Felipe Balbi @ 2010-04-14 6:47 UTC (permalink / raw)
To: Felipe Balbi; +Cc: gcc-help, iant
Hi,
On Wed, Apr 14, 2010 at 09:30:43AM +0300, Felipe Balbi wrote:
> I commented the for loop just to get the thing compiling and nm doesn't
> show any __start_ symbols:
now I got it working:
#include <stdio.h>
typedef int (*initcall_t)(void);
extern initcall_t __start__initcall[];
extern initcall_t __stop__initcall[];
static int my_init(void)
{
printf("hello world from _init\n");
}
static initcall_t __my_initcall_my_init
__attribute__((__used__))
__attribute__((section("_initcall"))) = my_init;
static void call_initcall(initcall_t fn)
{
fn();
}
int main(int argc, char *argv[])
{
initcall_t *fn;
for (fn = __start__initcall; fn
< __stop__initcall; fn++)
call_initcall(*fn);
return
0;
}
thanks a lot Ian and Andrew.
--
balbi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-14 6:30 ` Felipe Balbi
2010-04-14 6:47 ` Felipe Balbi
@ 2010-04-14 6:50 ` Fabian Cenedese
1 sibling, 0 replies; 8+ messages in thread
From: Fabian Cenedese @ 2010-04-14 6:50 UTC (permalink / raw)
To: gcc-help
>I commented the for loop just to get the thing compiling and nm doesn't
>show any __start_ symbols:
>
>$ nm tst | grep init
>080494cc d __init_array_end
>080494cc d __init_array_start
>08048400 T __libc_csu_init
>080495d4 d __my_initcall_my_init
>08048298 T _init
>080483c4 t my_init
Here's what we do for structures:
In the linker script:
PROVIDE (__HWDEVICE_DESC_BEGIN = .);
.struct_hw_dev_desc : {*(.struct_hw_dev_desc)} > ram
PROVIDE (__HWDEVICE_DESC_END = .);
In the code:
#define STRUCT_HW_DEV_DESC __attribute__ ((section (".struct_hw_dev_desc")))
STRUCT_HW_DEV_DESC SINOSHwDeviceDesc { definition }
extern char* __HWDEVICE_DESC_BEGIN[];
extern char* __HWDEVICE_DESC_END[];
SINOSHwDeviceDesc* desc = (SINOSHwDeviceDesc*) __HWDEVICE_DESC_BEGIN;
desc++;
And then you can use these values for whatever you want
until you reach __HWDEVICE_DESC_END.
bye Fabi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Figuring out start and end of sections
@ 2010-04-13 17:40 Felipe Balbi
2010-04-13 17:44 ` Andrew Haley
2010-04-14 0:24 ` Ian Lance Taylor
0 siblings, 2 replies; 8+ messages in thread
From: Felipe Balbi @ 2010-04-13 17:40 UTC (permalink / raw)
To: gcc-help
Hi all,
is there any way to figure out where a section starts and ends ?
I added a specific section to my program using
__attribute__((section "<section name>")) and now I want to figure out
where that section starts so I can iterate over it and call the function
pointers I'm adding to it.
Do I need a specific linker script to achieve that or does the default
scripts give me possibility to find that out ?
--
balbi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-13 17:40 Felipe Balbi
@ 2010-04-13 17:44 ` Andrew Haley
2010-04-14 0:24 ` Ian Lance Taylor
1 sibling, 0 replies; 8+ messages in thread
From: Andrew Haley @ 2010-04-13 17:44 UTC (permalink / raw)
To: gcc-help
On 04/13/2010 06:40 PM, Felipe Balbi wrote:
> is there any way to figure out where a section starts and ends ?
>
> I added a specific section to my program using
> __attribute__((section "<section name>")) and now I want to figure out
> where that section starts so I can iterate over it and call the function
> pointers I'm adding to it.
Terminate the list with a null pointer; AFAIK that's what everyone else
does. To get the start address, you just need to define a global variable
in that section. Of course this means you have to link everything in the
correct order.
Andrew.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-13 17:40 Felipe Balbi
2010-04-13 17:44 ` Andrew Haley
@ 2010-04-14 0:24 ` Ian Lance Taylor
2010-04-14 8:49 ` Andrew Haley
1 sibling, 1 reply; 8+ messages in thread
From: Ian Lance Taylor @ 2010-04-14 0:24 UTC (permalink / raw)
To: me; +Cc: gcc-help
Felipe Balbi <me@felipebalbi.com> writes:
> is there any way to figure out where a section starts and ends ?
>
> I added a specific section to my program using
> __attribute__((section "<section name>")) and now I want to figure out
> where that section starts so I can iterate over it and call the function
> pointers I'm adding to it.
>
> Do I need a specific linker script to achieve that or does the default
> scripts give me possibility to find that out ?
If you are using the GNU linker, or gold, and you make the section
name a valid C identifier, then the linker will automatically define
symbols __start_SECNAME and __stop_SECNAME which you can use.
Ian
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Figuring out start and end of sections
2010-04-14 0:24 ` Ian Lance Taylor
@ 2010-04-14 8:49 ` Andrew Haley
0 siblings, 0 replies; 8+ messages in thread
From: Andrew Haley @ 2010-04-14 8:49 UTC (permalink / raw)
To: gcc-help; +Cc: me
On 04/14/2010 01:24 AM, Ian Lance Taylor wrote:
> Felipe Balbi <me@felipebalbi.com> writes:
>
>> is there any way to figure out where a section starts and ends ?
>>
>> I added a specific section to my program using
>> __attribute__((section "<section name>")) and now I want to figure out
>> where that section starts so I can iterate over it and call the function
>> pointers I'm adding to it.
>>
>> Do I need a specific linker script to achieve that or does the default
>> scripts give me possibility to find that out ?
>
> If you are using the GNU linker, or gold, and you make the section
> name a valid C identifier, then the linker will automatically define
> symbols __start_SECNAME and __stop_SECNAME which you can use.
Ah, that's a much better idea. Forget my suggestion.
Andrew.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2010-04-14 6:21 Figuring out start and end of sections Felipe Balbi
2010-04-14 6:30 ` Felipe Balbi
2010-04-14 6:47 ` Felipe Balbi
2010-04-14 6:50 ` Fabian Cenedese
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2010-04-14 8:49 ` Andrew Haley
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