* redboot fconfig crash with gcc 4.3.2
@ 2009-01-19 22:23 Jose Vasconcellos
2009-01-20 7:55 ` Gary Thomas
0 siblings, 1 reply; 4+ messages in thread
From: Jose Vasconcellos @ 2009-01-19 22:23 UTC (permalink / raw)
To: ecos-patches
Redboot gets an exception when trying to set any IP address with fconfig
when using gcc-4.3.2 on an ixp425 target (armeb). The issue seems to be
an alignment problem as val_ptr contains an odd address; it looks like gcc
is optimizing and trying to do a copy on a word boundary. The removal of
the cast fixes the problem.
--- fconfig.c 2009-01-18 14:34:11.000000000 -0500
+++ fconfig.c.new 2009-01-18 14:35:22.000000000 -0500
@@ -388,7 +388,7 @@
break;
#ifdef CYGPKG_REDBOOT_NETWORKING
case CONFIG_IP:
- memcpy(&hold_ip_val.s_addr, &((in_addr_t *)val_ptr)->s_addr, sizeof(in_addr_t));
+ memcpy(&hold_ip_val.s_addr, val_ptr, sizeof(in_addr_t));
if (!_gethostbyname(line, &new_ip_val)) {
return CONFIG_BAD;
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: redboot fconfig crash with gcc 4.3.2
2009-01-19 22:23 redboot fconfig crash with gcc 4.3.2 Jose Vasconcellos
@ 2009-01-20 7:55 ` Gary Thomas
2009-01-20 9:20 ` Daniel Néri
2009-01-20 13:19 ` Jose Vasconcellos
0 siblings, 2 replies; 4+ messages in thread
From: Gary Thomas @ 2009-01-20 7:55 UTC (permalink / raw)
To: Jose Vasconcellos; +Cc: ecos-patches
Jose Vasconcellos wrote:
> Redboot gets an exception when trying to set any IP address with fconfig
> when using gcc-4.3.2 on an ixp425 target (armeb). The issue seems to be
> an alignment problem as val_ptr contains an odd address; it looks like gcc
> is optimizing and trying to do a copy on a word boundary. The removal of
> the cast fixes the problem.
>
>
> --- fconfig.c 2009-01-18 14:34:11.000000000 -0500
> +++ fconfig.c.new 2009-01-18 14:35:22.000000000 -0500
> @@ -388,7 +388,7 @@
> break;
> #ifdef CYGPKG_REDBOOT_NETWORKING
> case CONFIG_IP:
> - memcpy(&hold_ip_val.s_addr, &((in_addr_t *)val_ptr)->s_addr,
> sizeof(in_addr_t));
> + memcpy(&hold_ip_val.s_addr, val_ptr, sizeof(in_addr_t));
> if (!_gethostbyname(line, &new_ip_val)) {
> return CONFIG_BAD;
> }
>
Sounds like a *BUG* in the compiler. Have you reported it?
This does more than remove the cast :-) What if the s_addr field is not
at the start of the structure? I know it hasn't moved in 25+ years, but
I don't like tossing correctness [even if only pedantic] away.
Maybe there's another way to solve this. Does it happen on arm[el]?
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
------------------------------------------------------------
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: redboot fconfig crash with gcc 4.3.2
2009-01-20 7:55 ` Gary Thomas
@ 2009-01-20 9:20 ` Daniel Néri
2009-01-20 13:19 ` Jose Vasconcellos
1 sibling, 0 replies; 4+ messages in thread
From: Daniel Néri @ 2009-01-20 9:20 UTC (permalink / raw)
To: ecos-patches
Gary Thomas <gary@mlbassoc.com> writes:
> Jose Vasconcellos wrote:
>> Redboot gets an exception when trying to set any IP address with fconfig
>> when using gcc-4.3.2 on an ixp425 target (armeb). The issue seems to be
>> an alignment problem as val_ptr contains an odd address; it looks like gcc
>> is optimizing and trying to do a copy on a word boundary. The removal of
>> the cast fixes the problem.
>>
>>
>> --- fconfig.c 2009-01-18 14:34:11.000000000 -0500
>> +++ fconfig.c.new 2009-01-18 14:35:22.000000000 -0500
>> @@ -388,7 +388,7 @@
>> break;
>> #ifdef CYGPKG_REDBOOT_NETWORKING
>> case CONFIG_IP:
>> - memcpy(&hold_ip_val.s_addr, &((in_addr_t
>> *)val_ptr)->s_addr, sizeof(in_addr_t));
>> + memcpy(&hold_ip_val.s_addr, val_ptr, sizeof(in_addr_t));
>> if (!_gethostbyname(line, &new_ip_val)) {
>> return CONFIG_BAD;
>> }
>>
>
> Sounds like a *BUG* in the compiler.
I don'think so -- standard behaviour is undefined when converting from a
pointer to one type to a pointer to another type that has more stringent
alignment requirements (e.g. from "void *" to "in_addr_t *").
Regards,
--
Daniel Néri <daniel.neri@sigicom.com>
Sigicom AB, Stockholm, Sweden
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: redboot fconfig crash with gcc 4.3.2
2009-01-20 7:55 ` Gary Thomas
2009-01-20 9:20 ` Daniel Néri
@ 2009-01-20 13:19 ` Jose Vasconcellos
1 sibling, 0 replies; 4+ messages in thread
From: Jose Vasconcellos @ 2009-01-20 13:19 UTC (permalink / raw)
To: Gary Thomas; +Cc: ecos-patches
Gary Thomas wrote:
> Jose Vasconcellos wrote:
>> Redboot gets an exception when trying to set any IP address with fconfig
>> when using gcc-4.3.2 on an ixp425 target (armeb). The issue seems to be
>> an alignment problem as val_ptr contains an odd address; it looks
>> like gcc
>> is optimizing and trying to do a copy on a word boundary. The removal of
>> the cast fixes the problem.
>>
>>
>> --- fconfig.c 2009-01-18 14:34:11.000000000 -0500
>> +++ fconfig.c.new 2009-01-18 14:35:22.000000000 -0500
>> @@ -388,7 +388,7 @@
>> break;
>> #ifdef CYGPKG_REDBOOT_NETWORKING
>> case CONFIG_IP:
>> - memcpy(&hold_ip_val.s_addr, &((in_addr_t *)val_ptr)->s_addr,
>> sizeof(in_addr_t));
>> + memcpy(&hold_ip_val.s_addr, val_ptr, sizeof(in_addr_t));
>> if (!_gethostbyname(line, &new_ip_val)) {
>> return CONFIG_BAD;
>> }
>>
>
> Sounds like a *BUG* in the compiler. Have you reported it?
>
> This does more than remove the cast :-) What if the s_addr field is not
> at the start of the structure? I know it hasn't moved in 25+ years, but
> I don't like tossing correctness [even if only pedantic] away.
>
> Maybe there's another way to solve this. Does it happen on arm[el]?
>
This doesn't look like a compiler bug to me. I suspect that this problem
affects other arm variants but I only have access to an ixp425. The code
is incorrect as val_ptr is pointing to a place in a configuration buffer for
the raw data. Imposing (via a cast) the structure is not the right solution.
Note that a few lines down in the source, the copy in the other direction
does not have such a cast.
Jose
^ permalink raw reply [flat|nested] 4+ messages in thread
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2009-01-19 22:23 redboot fconfig crash with gcc 4.3.2 Jose Vasconcellos
2009-01-20 7:55 ` Gary Thomas
2009-01-20 9:20 ` Daniel Néri
2009-01-20 13:19 ` Jose Vasconcellos
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