Re: [PATCH] drm/amd/powerplay/smu10_hwmgr: use struct_size() in kzalloc()

[Alex Deucher]

On Tue, Feb 19, 2019 at 1:55 PM Gustavo A. R. Silva
<gustavo@xxxxxxxxxxxxxx> wrote:
>
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
>     int stuff;
>     struct boo entry[];
> };
>
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = kzalloc(size, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> Notice that, in this case, variable table_size is not necessary, hence
> it is removed.
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>

Applied this and the smu8 patch.  Thanks!

Alex

> ---
>  drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c | 8 +++-----
>  1 file 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 5273de3c5b98..0ad8fe4a6277 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
> @@ -139,12 +139,10 @@ static int smu10_construct_max_power_limits_table(struct pp_hwmgr *hwmgr,
>  static int smu10_init_dynamic_state_adjustment_rule_settings(
>                                                         struct pp_hwmgr *hwmgr)
>  {
> -       uint32_t table_size =
> -               sizeof(struct phm_clock_voltage_dependency_table) +
> -               (7 * sizeof(struct phm_clock_voltage_dependency_record));
> +       struct phm_clock_voltage_dependency_table *table_clk_vlt;
>
> -       struct phm_clock_voltage_dependency_table *table_clk_vlt =
> -                                       kzalloc(table_size, GFP_KERNEL);
> +       table_clk_vlt = kzalloc(struct_size(table_clk_vlt, entries, 7),
> +                               GFP_KERNEL);
>
>         if (NULL == table_clk_vlt) {
>                 pr_err("Can not allocate memory!\n");
> --
> 2.20.1
>
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