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* [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper
@ 2020-05-19 22:55 Gustavo A. R. Silva
  2020-05-20  7:42 ` Christian König
  0 siblings, 1 reply; 5+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-19 22:55 UTC (permalink / raw)
  To: Evan Quan, Alex Deucher, Christian König, David Airlie,
	Daniel Vetter
  Cc: Gustavo A. R. Silva, dri-devel, amd-gfx, linux-kernel

The current codebase makes use of one-element arrays in the following
form:

struct something {
    int length;
    u8 data[1];
};

struct something *instance;

instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
instance->length = size;
memcpy(instance->data, source, size);

but the preferred mechanism to declare variable-length types such as
these ones is a flexible array member[1][2], introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on. So, replace
the one-element array with a flexible-array member.

Also, make use of the new struct_size() helper to properly calculate the
size of struct smu10_voltage_dependency_table.

This issue was found with the help of Coccinelle and, audited and fixed
_manually_.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c | 6 ++----
 drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h | 2 +-
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
index 246bb9ac557d8..c9cfe90a29471 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
+++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
@@ -410,12 +410,10 @@ static int smu10_get_clock_voltage_dependency_table(struct pp_hwmgr *hwmgr,
 			struct smu10_voltage_dependency_table **pptable,
 			uint32_t num_entry, const DpmClock_t *pclk_dependency_table)
 {
-	uint32_t table_size, i;
+	uint32_t i;
 	struct smu10_voltage_dependency_table *ptable;
 
-	table_size = sizeof(uint32_t) + sizeof(struct smu10_voltage_dependency_table) * num_entry;
-	ptable = kzalloc(table_size, GFP_KERNEL);
-
+	ptable = kzalloc(struct_size(ptable, entries, num_entry), GFP_KERNEL);
 	if (NULL == ptable)
 		return -ENOMEM;
 
diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
index 1fb296a996f3a..0f969de10fabc 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
+++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
@@ -192,7 +192,7 @@ struct smu10_clock_voltage_dependency_record {
 
 struct smu10_voltage_dependency_table {
 	uint32_t count;
-	struct smu10_clock_voltage_dependency_record entries[1];
+	struct smu10_clock_voltage_dependency_record entries[];
 };
 
 struct smu10_clock_voltage_information {
-- 
2.26.2

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^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper
  2020-05-19 22:55 [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper Gustavo A. R. Silva
@ 2020-05-20  7:42 ` Christian König
  2020-05-20 18:17   ` Alex Deucher
  2020-05-22 17:51   ` Gustavo A. R. Silva
  0 siblings, 2 replies; 5+ messages in thread
From: Christian König @ 2020-05-20  7:42 UTC (permalink / raw)
  To: Gustavo A. R. Silva, Evan Quan, Alex Deucher, David Airlie,
	Daniel Vetter
  Cc: Gustavo A. R. Silva, dri-devel, amd-gfx, linux-kernel

Am 20.05.20 um 00:55 schrieb Gustavo A. R. Silva:
> The current codebase makes use of one-element arrays in the following
> form:
>
> struct something {
>      int length;
>      u8 data[1];
> };
>
> struct something *instance;
>
> instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> instance->length = size;
> memcpy(instance->data, source, size);
>
> but the preferred mechanism to declare variable-length types such as
> these ones is a flexible array member[1][2], introduced in C99:
>
> struct foo {
>          int stuff;
>          struct boo array[];
> };
>
> By making use of the mechanism above, we will get a compiler warning
> in case the flexible array does not occur last in the structure, which
> will help us prevent some kind of undefined behavior bugs from being
> inadvertently introduced[3] to the codebase from now on. So, replace
> the one-element array with a flexible-array member.
>
> Also, make use of the new struct_size() helper to properly calculate the
> size of struct smu10_voltage_dependency_table.
>
> This issue was found with the help of Coccinelle and, audited and fixed
> _manually_.
>
> [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fonlinedocs%2Fgcc%2FZero-Length.html&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C8a400bdb88924a1d951508d7fc471966%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637255254622039268&amp;sdata=ILOPPn17c%2B3oyLLdh%2BgH2b%2B8RdhWuTFGxruRD7GUHOo%3D&amp;reserved=0
> [2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FKSPP%2Flinux%2Fissues%2F21&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C8a400bdb88924a1d951508d7fc471966%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637255254622039268&amp;sdata=lCr5Otij55Snq27BDp4RmtW4hNhOS%2Bm4vSUOOAz07XA%3D&amp;reserved=0
> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Acked-by: Christian König <christian.koenig@amd.com>

May I suggest that we add a section how to correctly do this to 
Documentation/process/coding-style.rst or similar document?

I've seen a bunch of different approaches and some even doesn't work 
with some gcc versions and result in a broken binary.

Thanks,
Christian.

> ---
>   drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c | 6 ++----
>   drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h | 2 +-
>   2 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> index 246bb9ac557d8..c9cfe90a29471 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> @@ -410,12 +410,10 @@ static int smu10_get_clock_voltage_dependency_table(struct pp_hwmgr *hwmgr,
>   			struct smu10_voltage_dependency_table **pptable,
>   			uint32_t num_entry, const DpmClock_t *pclk_dependency_table)
>   {
> -	uint32_t table_size, i;
> +	uint32_t i;
>   	struct smu10_voltage_dependency_table *ptable;
>   
> -	table_size = sizeof(uint32_t) + sizeof(struct smu10_voltage_dependency_table) * num_entry;
> -	ptable = kzalloc(table_size, GFP_KERNEL);
> -
> +	ptable = kzalloc(struct_size(ptable, entries, num_entry), GFP_KERNEL);
>   	if (NULL == ptable)
>   		return -ENOMEM;
>   
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> index 1fb296a996f3a..0f969de10fabc 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> @@ -192,7 +192,7 @@ struct smu10_clock_voltage_dependency_record {
>   
>   struct smu10_voltage_dependency_table {
>   	uint32_t count;
> -	struct smu10_clock_voltage_dependency_record entries[1];
> +	struct smu10_clock_voltage_dependency_record entries[];
>   };
>   
>   struct smu10_clock_voltage_information {

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https://lists.freedesktop.org/mailman/listinfo/dri-devel

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper
  2020-05-20  7:42 ` Christian König
@ 2020-05-20 18:17   ` Alex Deucher
  2020-05-22 17:51   ` Gustavo A. R. Silva
  1 sibling, 0 replies; 5+ messages in thread
From: Alex Deucher @ 2020-05-20 18:17 UTC (permalink / raw)
  To: Christian König
  Cc: Gustavo A. R. Silva, David Airlie, Gustavo A. R. Silva,
	Maling list - DRI developers, LKML, amd-gfx list, Alex Deucher,
	Evan Quan

Applied.  thanks!

Alex

On Wed, May 20, 2020 at 3:42 AM Christian König
<christian.koenig@amd.com> wrote:
>
> Am 20.05.20 um 00:55 schrieb Gustavo A. R. Silva:
> > The current codebase makes use of one-element arrays in the following
> > form:
> >
> > struct something {
> >      int length;
> >      u8 data[1];
> > };
> >
> > struct something *instance;
> >
> > instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> > instance->length = size;
> > memcpy(instance->data, source, size);
> >
> > but the preferred mechanism to declare variable-length types such as
> > these ones is a flexible array member[1][2], introduced in C99:
> >
> > struct foo {
> >          int stuff;
> >          struct boo array[];
> > };
> >
> > By making use of the mechanism above, we will get a compiler warning
> > in case the flexible array does not occur last in the structure, which
> > will help us prevent some kind of undefined behavior bugs from being
> > inadvertently introduced[3] to the codebase from now on. So, replace
> > the one-element array with a flexible-array member.
> >
> > Also, make use of the new struct_size() helper to properly calculate the
> > size of struct smu10_voltage_dependency_table.
> >
> > This issue was found with the help of Coccinelle and, audited and fixed
> > _manually_.
> >
> > [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fonlinedocs%2Fgcc%2FZero-Length.html&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C8a400bdb88924a1d951508d7fc471966%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637255254622039268&amp;sdata=ILOPPn17c%2B3oyLLdh%2BgH2b%2B8RdhWuTFGxruRD7GUHOo%3D&amp;reserved=0
> > [2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FKSPP%2Flinux%2Fissues%2F21&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C8a400bdb88924a1d951508d7fc471966%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637255254622039268&amp;sdata=lCr5Otij55Snq27BDp4RmtW4hNhOS%2Bm4vSUOOAz07XA%3D&amp;reserved=0
> > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
> >
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>
> Acked-by: Christian König <christian.koenig@amd.com>
>
> May I suggest that we add a section how to correctly do this to
> Documentation/process/coding-style.rst or similar document?
>
> I've seen a bunch of different approaches and some even doesn't work
> with some gcc versions and result in a broken binary.
>
> Thanks,
> Christian.
>
> > ---
> >   drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c | 6 ++----
> >   drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h | 2 +-
> >   2 files changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> > index 246bb9ac557d8..c9cfe90a29471 100644
> > --- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> > +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> > @@ -410,12 +410,10 @@ static int smu10_get_clock_voltage_dependency_table(struct pp_hwmgr *hwmgr,
> >                       struct smu10_voltage_dependency_table **pptable,
> >                       uint32_t num_entry, const DpmClock_t *pclk_dependency_table)
> >   {
> > -     uint32_t table_size, i;
> > +     uint32_t i;
> >       struct smu10_voltage_dependency_table *ptable;
> >
> > -     table_size = sizeof(uint32_t) + sizeof(struct smu10_voltage_dependency_table) * num_entry;
> > -     ptable = kzalloc(table_size, GFP_KERNEL);
> > -
> > +     ptable = kzalloc(struct_size(ptable, entries, num_entry), GFP_KERNEL);
> >       if (NULL == ptable)
> >               return -ENOMEM;
> >
> > diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> > index 1fb296a996f3a..0f969de10fabc 100644
> > --- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> > +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
> > @@ -192,7 +192,7 @@ struct smu10_clock_voltage_dependency_record {
> >
> >   struct smu10_voltage_dependency_table {
> >       uint32_t count;
> > -     struct smu10_clock_voltage_dependency_record entries[1];
> > +     struct smu10_clock_voltage_dependency_record entries[];
> >   };
> >
> >   struct smu10_clock_voltage_information {
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
_______________________________________________
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^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper
  2020-05-20  7:42 ` Christian König
  2020-05-20 18:17   ` Alex Deucher
@ 2020-05-22 17:51   ` Gustavo A. R. Silva
  2020-05-22 17:54     ` Alex Deucher
  1 sibling, 1 reply; 5+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-22 17:51 UTC (permalink / raw)
  To: Christian König
  Cc: Gustavo A. R. Silva, David Airlie, linux-kernel, dri-devel,
	amd-gfx, Alex Deucher, Evan Quan

On Wed, May 20, 2020 at 09:42:27AM +0200, Christian König wrote:
> > 
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> Acked-by: Christian König <christian.koenig@amd.com>
> 
> May I suggest that we add a section how to correctly do this to
> Documentation/process/coding-style.rst or similar document?
> 

That's already on my list. :)

> I've seen a bunch of different approaches and some even doesn't work with
> some gcc versions and result in a broken binary.
> 

Do you have an example of that one that doesn't work with some GCC
versions? It'd be interesting to take a look...

Thanks
--
Gustavo
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper
  2020-05-22 17:51   ` Gustavo A. R. Silva
@ 2020-05-22 17:54     ` Alex Deucher
  0 siblings, 0 replies; 5+ messages in thread
From: Alex Deucher @ 2020-05-22 17:54 UTC (permalink / raw)
  To: Gustavo A. R. Silva
  Cc: Gustavo A. R. Silva, David Airlie, LKML, amd-gfx list,
	Maling list - DRI developers, Alex Deucher, Evan Quan,
	Christian König

On Fri, May 22, 2020 at 1:46 PM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
>
> On Wed, May 20, 2020 at 09:42:27AM +0200, Christian König wrote:
> > >
> > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> >
> > Acked-by: Christian König <christian.koenig@amd.com>
> >
> > May I suggest that we add a section how to correctly do this to
> > Documentation/process/coding-style.rst or similar document?
> >
>
> That's already on my list. :)
>
> > I've seen a bunch of different approaches and some even doesn't work with
> > some gcc versions and result in a broken binary.
> >
>
> Do you have an example of that one that doesn't work with some GCC
> versions? It'd be interesting to take a look...

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/radeon/radeon_atombios.c?id=a7ee824a6255e347ea76e2f00827e81bbe01004e

Alex

>
> Thanks
> --
> Gustavo
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
_______________________________________________
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https://lists.freedesktop.org/mailman/listinfo/dri-devel

^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-19 22:55 [PATCH] drm/amdgpu/smu10: Replace one-element array and use struct_size() helper Gustavo A. R. Silva
2020-05-20  7:42 ` Christian König
2020-05-20 18:17   ` Alex Deucher
2020-05-22 17:51   ` Gustavo A. R. Silva
2020-05-22 17:54     ` Alex Deucher

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