* linux-next 20190611: objtool warning
@ 2019-06-12 1:59 Randy Dunlap
2019-06-12 2:52 ` Josh Poimboeuf
0 siblings, 1 reply; 4+ messages in thread
From: Randy Dunlap @ 2019-06-12 1:59 UTC (permalink / raw)
To: linux-next@vger•kernel.org, LKML, Josh Poimboeuf, Peter Zijlstra
Hi,
New warning AFAIK:
drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0x11f: sibling call from callable instruction with modified stack frame
> gcc --version
gcc (SUSE Linux) 7.4.1 20190424 [gcc-7-branch revision 270538]
--
~Randy
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: linux-next 20190611: objtool warning
2019-06-12 1:59 linux-next 20190611: objtool warning Randy Dunlap
@ 2019-06-12 2:52 ` Josh Poimboeuf
2019-06-12 3:17 ` Randy Dunlap
2019-06-12 5:09 ` Guenter Roeck
0 siblings, 2 replies; 4+ messages in thread
From: Josh Poimboeuf @ 2019-06-12 2:52 UTC (permalink / raw)
To: Randy Dunlap
Cc: linux-next@vger•kernel.org, LKML, Peter Zijlstra, Masahiro Yamada,
Guenter Roeck, Jean Delvare
On Tue, Jun 11, 2019 at 06:59:22PM -0700, Randy Dunlap wrote:
> Hi,
>
> New warning AFAIK:
>
> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0x11f: sibling call from callable instruction with modified stack frame
I'm getting a different warning:
drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
But I bet the root cause is the same.
This fixes it for me:
From: Josh Poimboeuf <jpoimboe@redhat•com>
Subject: [PATCH] hwmon/smsc47m1: Fix objtool warning caused by undefined behavior
Objtool is reporting the following warning:
drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
It's apparently caused by
2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
which is somehow convincing GCC to add a jump past the end of the
function:
793: 45 85 ed test %r13d,%r13d
796: 0f 88 9e 01 00 00 js 93a <fan_div_store+0x25a>
...
930: e9 5e fe ff ff jmpq 793 <fan_div_store+0xb3>
935: e8 00 00 00 00 callq 93a <fan_div_store+0x25a>
936: R_X86_64_PLT32 __stack_chk_fail-0x4
<function end>
I suppose this falls under the category of undefined behavior, so we
probably can't call it a GCC bug. But if the value of "nr" were out of
range somehow then it would start executing random code. Use a runtime
BUG() assertion to avoid undefined behavior.
Fixes: 2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
Reported-by: Randy Dunlap <rdunlap@infradead•org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat•com>
---
drivers/hwmon/smsc47m1.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
index 6d366c9cb906..b637836b58a1 100644
--- a/drivers/hwmon/smsc47m1.c
+++ b/drivers/hwmon/smsc47m1.c
@@ -352,7 +352,7 @@ static ssize_t fan_div_store(struct device *dev,
smsc47m1_write_value(data, SMSC47M2_REG_FANDIV3, tmp);
break;
default:
- unreachable();
+ BUG();
}
/* Preserve fan min */
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: linux-next 20190611: objtool warning
2019-06-12 2:52 ` Josh Poimboeuf
@ 2019-06-12 3:17 ` Randy Dunlap
2019-06-12 5:09 ` Guenter Roeck
1 sibling, 0 replies; 4+ messages in thread
From: Randy Dunlap @ 2019-06-12 3:17 UTC (permalink / raw)
To: Josh Poimboeuf
Cc: linux-next@vger•kernel.org, LKML, Peter Zijlstra, Masahiro Yamada,
Guenter Roeck, Jean Delvare
On 6/11/19 7:52 PM, Josh Poimboeuf wrote:
> On Tue, Jun 11, 2019 at 06:59:22PM -0700, Randy Dunlap wrote:
>> Hi,
>>
>> New warning AFAIK:
>>
>> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0x11f: sibling call from callable instruction with modified stack frame
>
> I'm getting a different warning:
>
> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
>
> But I bet the root cause is the same.
>
> This fixes it for me:
>
> From: Josh Poimboeuf <jpoimboe@redhat•com>
> Subject: [PATCH] hwmon/smsc47m1: Fix objtool warning caused by undefined behavior
>
> Objtool is reporting the following warning:
>
> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
>
> It's apparently caused by
>
> 2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
>
> which is somehow convincing GCC to add a jump past the end of the
> function:
>
> 793: 45 85 ed test %r13d,%r13d
> 796: 0f 88 9e 01 00 00 js 93a <fan_div_store+0x25a>
> ...
> 930: e9 5e fe ff ff jmpq 793 <fan_div_store+0xb3>
> 935: e8 00 00 00 00 callq 93a <fan_div_store+0x25a>
> 936: R_X86_64_PLT32 __stack_chk_fail-0x4
> <function end>
>
> I suppose this falls under the category of undefined behavior, so we
> probably can't call it a GCC bug. But if the value of "nr" were out of
> range somehow then it would start executing random code. Use a runtime
> BUG() assertion to avoid undefined behavior.
>
> Fixes: 2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
> Reported-by: Randy Dunlap <rdunlap@infradead•org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat•com>
Yes, that works for me. Thanks.
Acked-by: Randy Dunlap <rdunlap@infradead•org>
> ---
> drivers/hwmon/smsc47m1.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
> index 6d366c9cb906..b637836b58a1 100644
> --- a/drivers/hwmon/smsc47m1.c
> +++ b/drivers/hwmon/smsc47m1.c
> @@ -352,7 +352,7 @@ static ssize_t fan_div_store(struct device *dev,
> smsc47m1_write_value(data, SMSC47M2_REG_FANDIV3, tmp);
> break;
> default:
> - unreachable();
> + BUG();
> }
>
> /* Preserve fan min */
>
--
~Randy
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: linux-next 20190611: objtool warning
2019-06-12 2:52 ` Josh Poimboeuf
2019-06-12 3:17 ` Randy Dunlap
@ 2019-06-12 5:09 ` Guenter Roeck
1 sibling, 0 replies; 4+ messages in thread
From: Guenter Roeck @ 2019-06-12 5:09 UTC (permalink / raw)
To: Josh Poimboeuf, Randy Dunlap
Cc: linux-next@vger•kernel.org, LKML, Peter Zijlstra, Masahiro Yamada,
Jean Delvare
On 6/11/19 7:52 PM, Josh Poimboeuf wrote:
> On Tue, Jun 11, 2019 at 06:59:22PM -0700, Randy Dunlap wrote:
>> Hi,
>>
>> New warning AFAIK:
>>
>> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0x11f: sibling call from callable instruction with modified stack frame
>
> I'm getting a different warning:
>
> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
>
> But I bet the root cause is the same.
>
> This fixes it for me:
>
> From: Josh Poimboeuf <jpoimboe@redhat•com>
> Subject: [PATCH] hwmon/smsc47m1: Fix objtool warning caused by undefined behavior
>
> Objtool is reporting the following warning:
>
> drivers/hwmon/smsc47m1.o: warning: objtool: fan_div_store()+0xb6: can't find jump dest instruction at .text+0x93a
>
> It's apparently caused by
>
> 2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
>
> which is somehow convincing GCC to add a jump past the end of the
> function:
>
> 793: 45 85 ed test %r13d,%r13d
> 796: 0f 88 9e 01 00 00 js 93a <fan_div_store+0x25a>
> ...
> 930: e9 5e fe ff ff jmpq 793 <fan_div_store+0xb3>
> 935: e8 00 00 00 00 callq 93a <fan_div_store+0x25a>
> 936: R_X86_64_PLT32 __stack_chk_fail-0x4
> <function end>
>
> I suppose this falls under the category of undefined behavior, so we
> probably can't call it a GCC bug. But if the value of "nr" were out of
> range somehow then it would start executing random code. Use a runtime
> BUG() assertion to avoid undefined behavior.
>
> Fixes: 2cf6745e69d1 ("hwmon: (smsc47m1) fix (suspicious) outside array bounds warnings")
> Reported-by: Randy Dunlap <rdunlap@infradead•org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat•com>
> ---
> drivers/hwmon/smsc47m1.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
> index 6d366c9cb906..b637836b58a1 100644
> --- a/drivers/hwmon/smsc47m1.c
> +++ b/drivers/hwmon/smsc47m1.c
> @@ -352,7 +352,7 @@ static ssize_t fan_div_store(struct device *dev,
> smsc47m1_write_value(data, SMSC47M2_REG_FANDIV3, tmp);
> break;
> default:
> - unreachable();
> + BUG();
Sigh. And I wanted to avoid BUG() because this is all just to make
the compiler happy to start with. Oh well. I updated the offending
patch to use BUG().
Guenter
> }
>
> /* Preserve fan min */
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-06-12 1:59 linux-next 20190611: objtool warning Randy Dunlap
2019-06-12 2:52 ` Josh Poimboeuf
2019-06-12 3:17 ` Randy Dunlap
2019-06-12 5:09 ` Guenter Roeck
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