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SubjectRe: [PATCH v2 4/4] powerpc/pseries: use of_property_alloc/free() and of_node_alloc()
Le Fri, 3 Jun 2022 15:14:07 -0500,
Rob Herring <robh@kernel.org> a écrit :

> > static struct device_node *dlpar_parse_cc_node(struct cc_workarea *ccwa)
> > {
> > - struct device_node *dn;
> > const char *name;
> >
> > - dn = kzalloc(sizeof(*dn), GFP_KERNEL);
> > - if (!dn)
> > - return NULL;
> > -
> > name = (const char *)ccwa + be32_to_cpu(ccwa->name_offset);
> > - dn->full_name = kstrdup(name, GFP_KERNEL);
> > - if (!dn->full_name) {
> > - kfree(dn);
> > - return NULL;
> > - }
> >
> > - of_node_set_flag(dn, OF_DYNAMIC);
> > - of_node_init(dn);
> > -
> > - return dn;
> > + return of_node_alloc(name, GFP_KERNEL);
>
> Do you have any need for different flags? I can't really see a need for
> atomic or dma allocs or ???, so drop it I think.

Hum no, i copied this behavior from an existing function. I'll remove
that.

>
> > }
> >
> > static void dlpar_free_one_cc_node(struct device_node *dn)
> > @@ -102,11 +66,10 @@ static void dlpar_free_one_cc_node(struct device_node *dn)
> > while (dn->properties) {
> > prop = dn->properties;
> > dn->properties = prop->next;
> > - dlpar_free_cc_property(prop);
> > + of_property_free(prop);
>
> We should be able to just put the node and all the properties already
> attached will be freed.

Indeed !

>
> Looking at the history of this code, it originally did the kref_init
> much later in dlpar_attach_node(). So there was a window of allocating
> the node and adding properties where you'd need to manually free
> everything. Now that the node is referenced from the start, a put should
> free everything.
>
> > @@ -91,9 +82,7 @@ static void release_prop_list(const struct property *prop)
> > struct property *next;
> > for (; prop; prop = next) {
> > next = prop->next;
> > - kfree(prop->name);
> > - kfree(prop->value);
> > - kfree(prop);
> > + of_property_free(prop);
>
> Looks like you need this because code does: alloc properties, alloc
> node, add properties, attach node. It would need to be refactored to
> alloc the node first, but that's a bit more complex needing someone to
> test on pSeries.

Acked.

>
> > }
> >
> > }
> > @@ -167,27 +156,17 @@ static char * parse_next_property(char *buf, char *end, char **name, int *length
> > static struct property *new_property(const char *name, const int length,
> > const unsigned char *value, struct property *last)
> > {
> > - struct property *new = kzalloc(sizeof(*new), GFP_KERNEL);
> > + struct property *prop;
> >
> > - if (!new)
> > + prop = of_property_alloc(name, NULL, length + 1, GFP_KERNEL);
> > + if (!prop)
> > return NULL;
> >
> > - if (!(new->name = kstrdup(name, GFP_KERNEL)))
> > - goto cleanup;
> > - if (!(new->value = kmalloc(length + 1, GFP_KERNEL)))
> > - goto cleanup;
> > -
> > - memcpy(new->value, value, length);
> > - *(((char *)new->value) + length) = 0;
> > - new->length = length;
> > - new->next = last;
> > - return new;
> > -
> > -cleanup:
> > - kfree(new->name);
> > - kfree(new->value);
> > - kfree(new);
> > - return NULL;
> > + memcpy(prop->value, value, length);
> > + *(((char *)prop->value) + length) = 0;
>
> Looks to me like this could be avoided with this change:
>
> diff --git a/arch/powerpc/platforms/pseries/reconfig.c b/arch/powerpc/platforms/pseries/reconfig.c
> index cad7a0c93117..614753fc5f27 100644
> --- a/arch/powerpc/platforms/pseries/reconfig.c
> +++ b/arch/powerpc/platforms/pseries/reconfig.c
> @@ -148,7 +148,7 @@ static char * parse_next_property(char *buf, char *end, char **name, int *length
> /* now we're on the value */
> *value = tmp;
> tmp += *length;
> - if (tmp > end) {
> + if (tmp >= end) {
> printk(KERN_ERR "property parse failed in %s at line %d\n",
> __func__, __LINE__);
> return NULL;
> @@ -158,6 +158,7 @@ static char * parse_next_property(char *buf, char *end, char **name, int *length
> __func__, __LINE__);
> return NULL;
> }
> + *tmp = '\0';
> tmp++;
>
> /* and now we should be on the next name, or the end */
>
>
> Based on the comments, 'buf' should be nul terminated, so I would think
> that tmp == end would be an error. But I really don't know.
>
> Really need some pSeries people to comment on all this.
>
> Another option is if value is NULL, then of_property_alloc() should
> ensure the buffer is zeroed. Then you just need the memcpy.

Probably looks like a safe behavior anyway to zero the value buffer.
I'll add that.

Thanks,

Clément

>
> Rob



--
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com

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