cpufreq: powernv: fix stack bloat and NR_CPUS limitation
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Message ID 20191018000431.1675281-1-jhubbard@nvidia.com
State Superseded, archived
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Series
  • cpufreq: powernv: fix stack bloat and NR_CPUS limitation
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Commit Message

John Hubbard Oct. 18, 2019, 12:04 a.m. UTC
The following build warning occurred on powerpc 64-bit builds:

drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This is due to putting 1024 bytes on the stack:

    unsigned int chip[256];

...and while looking at this, it also has a bug: it fails with a stack
overrun, if CONFIG_NR_CPUS > 256.

Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.

Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---

Hi,

I have only compile-tested this, so I would appreciate if anyone
could do a basic runtime test on it. But (famous last words) it
seems simple enough that I'm confident it's correct. oh boy. :)

thanks,
John Hubbard
NVIDIA

 drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

Comments

Viresh Kumar Oct. 18, 2019, 4:27 a.m. UTC | #1
On 17-10-19, 17:04, John Hubbard wrote:
> The following build warning occurred on powerpc 64-bit builds:
> 
> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]

How come we are catching this warning after 4 years ?

> 
> This is due to putting 1024 bytes on the stack:
> 
>     unsigned int chip[256];
> 
> ...and while looking at this, it also has a bug: it fails with a stack
> overrun, if CONFIG_NR_CPUS > 256.
> 
> Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
> 
> Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
> Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: linux-pm@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> 
> Hi,
> 
> I have only compile-tested this, so I would appreciate if anyone
> could do a basic runtime test on it. But (famous last words) it
> seems simple enough that I'm confident it's correct. oh boy. :)
> 
> thanks,
> John Hubbard
> NVIDIA
> 
>  drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index 6061850e59c9..78e04402125f 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -1041,9 +1041,14 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
>  
>  static int init_chip_info(void)
>  {
> -	unsigned int chip[256];
> +	unsigned int *chip;
>  	unsigned int cpu, i;
>  	unsigned int prev_chip_id = UINT_MAX;
> +	int ret = 0;
> +
> +	chip = kcalloc(CONFIG_NR_CPUS, sizeof(int), GFP_KERNEL);

                                       sizeof(*chip)

> +	if (!chips)

           (!chip)

> +		return -ENOMEM;
>  
>  	for_each_possible_cpu(cpu) {
>  		unsigned int id = cpu_to_chip_id(cpu);
> @@ -1055,8 +1060,10 @@ static int init_chip_info(void)
>  	}
>  
>  	chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
> -	if (!chips)
> -		return -ENOMEM;
> +	if (!chips) {
> +		ret = -ENOMEM;
> +		goto free_and_return;
> +	}
>  
>  	for (i = 0; i < nr_chips; i++) {
>  		chips[i].id = chip[i];
> @@ -1066,7 +1073,9 @@ static int init_chip_info(void)
>  			per_cpu(chip_info, cpu) =  &chips[i];
>  	}
>  
> -	return 0;
> +free_and_return:
> +	kfree(chip);
> +	return ret;
>  }
>  
>  static inline void clean_chip_info(void)
> -- 
> 2.23.0
John Hubbard Oct. 18, 2019, 4:34 a.m. UTC | #2
On 10/17/19 9:27 PM, Viresh Kumar wrote:
> On 17-10-19, 17:04, John Hubbard wrote:
>> The following build warning occurred on powerpc 64-bit builds:
>>
>> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
>> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> How come we are catching this warning after 4 years ?
> 

Newer compilers. And btw, I don't spend a lot of time in powerpc
code, so I just recently ran this, and I guess everyone has been on less
new compilers so far, it seems.

I used a gcc 8.1 cross compiler in this case:

$ $ /blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc -v
Using built-in specs.
COLLECT_GCC=/blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc
COLLECT_LTO_WRAPPER=/home/jhubbard/blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/../libexec/gcc/powerpc64-linux/8.1.0/lto-wrapper
Target: powerpc64-linux
Configured with: /home/arnd/git/gcc/configure --target=powerpc64-linux --enable-targets=all --prefix=/home/arnd/cross/x86_64/gcc-8.1.0-nolibc/powerpc64-linux --enable-languages=c --without-headers --disable-bootstrap --disable-nls --disable-threads --disable-shared --disable-libmudflap --disable-libssp --disable-libgomp --disable-decimal-float --disable-libquadmath --disable-libatomic --disable-libcc1 --disable-libmpx --enable-checking=release
Thread model: single
gcc version 8.1.0 (GCC) 



thanks,

John Hubbard
NVIDIA
Viresh Kumar Oct. 18, 2019, 4:38 a.m. UTC | #3
On 17-10-19, 21:34, John Hubbard wrote:
> On 10/17/19 9:27 PM, Viresh Kumar wrote:
> > On 17-10-19, 17:04, John Hubbard wrote:
> >> The following build warning occurred on powerpc 64-bit builds:
> >>
> >> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> >> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> > 
> > How come we are catching this warning after 4 years ?
> > 
> 
> Newer compilers. And btw, I don't spend a lot of time in powerpc
> code, so I just recently ran this, and I guess everyone has been on less
> new compilers so far, it seems.
> 
> I used a gcc 8.1 cross compiler in this case:

Hmm, okay.

I hope you haven't missed my actual review comments on your patch,
just wanted to make sure we don't end up waiting for each other
indefinitely here :)
John Hubbard Oct. 18, 2019, 4:41 a.m. UTC | #4
On 10/17/19 9:38 PM, Viresh Kumar wrote:
> On 17-10-19, 21:34, John Hubbard wrote:
>> On 10/17/19 9:27 PM, Viresh Kumar wrote:
>>> On 17-10-19, 17:04, John Hubbard wrote:
>>>> The following build warning occurred on powerpc 64-bit builds:
>>>>
>>>> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
>>>> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>>>
>>> How come we are catching this warning after 4 years ?
>>>
>>
>> Newer compilers. And btw, I don't spend a lot of time in powerpc
>> code, so I just recently ran this, and I guess everyone has been on less
>> new compilers so far, it seems.
>>
>> I used a gcc 8.1 cross compiler in this case:
> 
> Hmm, okay.
> 
> I hope you haven't missed my actual review comments on your patch,
> just wanted to make sure we don't end up waiting for each other
> indefinitely here :)
> 

Ha, I did overlook those. It's late around here, I guess. :)

I'll send a v2 with those changes. 

thanks,

John Hubbard
NVIDIA
Viresh Kumar Oct. 18, 2019, 4:50 a.m. UTC | #5
On 17-10-19, 21:41, John Hubbard wrote:
> On 10/17/19 9:38 PM, Viresh Kumar wrote:
> > On 17-10-19, 21:34, John Hubbard wrote:
> >> On 10/17/19 9:27 PM, Viresh Kumar wrote:
> >>> On 17-10-19, 17:04, John Hubbard wrote:
> >>>> The following build warning occurred on powerpc 64-bit builds:
> >>>>
> >>>> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> >>>> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >>>
> >>> How come we are catching this warning after 4 years ?
> >>>
> >>
> >> Newer compilers. And btw, I don't spend a lot of time in powerpc
> >> code, so I just recently ran this, and I guess everyone has been on less
> >> new compilers so far, it seems.
> >>
> >> I used a gcc 8.1 cross compiler in this case:
> > 
> > Hmm, okay.
> > 
> > I hope you haven't missed my actual review comments on your patch,
> > just wanted to make sure we don't end up waiting for each other
> > indefinitely here :)
> > 
> 
> Ha, I did overlook those. It's late around here, I guess. :)

Good that I reminded you then :)

Patch
diff mbox series

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 6061850e59c9..78e04402125f 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1041,9 +1041,14 @@  static struct cpufreq_driver powernv_cpufreq_driver = {
 
 static int init_chip_info(void)
 {
-	unsigned int chip[256];
+	unsigned int *chip;
 	unsigned int cpu, i;
 	unsigned int prev_chip_id = UINT_MAX;
+	int ret = 0;
+
+	chip = kcalloc(CONFIG_NR_CPUS, sizeof(int), GFP_KERNEL);
+	if (!chips)
+		return -ENOMEM;
 
 	for_each_possible_cpu(cpu) {
 		unsigned int id = cpu_to_chip_id(cpu);
@@ -1055,8 +1060,10 @@  static int init_chip_info(void)
 	}
 
 	chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
-	if (!chips)
-		return -ENOMEM;
+	if (!chips) {
+		ret = -ENOMEM;
+		goto free_and_return;
+	}
 
 	for (i = 0; i < nr_chips; i++) {
 		chips[i].id = chip[i];
@@ -1066,7 +1073,9 @@  static int init_chip_info(void)
 			per_cpu(chip_info, cpu) =  &chips[i];
 	}
 
-	return 0;
+free_and_return:
+	kfree(chip);
+	return ret;
 }
 
 static inline void clean_chip_info(void)