From 098accf2da940189f4d62d3514d17f8bb05dc6e1 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Thu, 13 Feb 2020 14:00:21 +0000 Subject: [PATCH] iommu: Use C99 flexible array in fwspec Although the 1-element array was a typical pre-C99 way to implement variable-length structures, and indeed is a fundamental construct in the APIs of certain other popular platforms, there's no good reason for it here (and in particular the sizeof() trick is far too "clever" for its own good). We can just as easily implement iommu_fwspec's preallocation behaviour using a standard flexible array member, so let's make it look the way most readers would expect. Signed-off-by: Robin Murphy Signed-off-by: Joerg Roedel --- drivers/iommu/iommu.c | 15 ++++++++------- include/linux/iommu.h | 2 +- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 3e3528436e0b2..660eea8d1d2fb 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2405,7 +2405,8 @@ int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode, if (fwspec) return ops == fwspec->ops ? 0 : -EINVAL; - fwspec = kzalloc(sizeof(*fwspec), GFP_KERNEL); + /* Preallocate for the overwhelmingly common case of 1 ID */ + fwspec = kzalloc(struct_size(fwspec, ids, 1), GFP_KERNEL); if (!fwspec) return -ENOMEM; @@ -2432,15 +2433,15 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_free); int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids) { struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev); - size_t size; - int i; + int i, new_num; if (!fwspec) return -EINVAL; - size = offsetof(struct iommu_fwspec, ids[fwspec->num_ids + num_ids]); - if (size > sizeof(*fwspec)) { - fwspec = krealloc(fwspec, size, GFP_KERNEL); + new_num = fwspec->num_ids + num_ids; + if (new_num > 1) { + fwspec = krealloc(fwspec, struct_size(fwspec, ids, new_num), + GFP_KERNEL); if (!fwspec) return -ENOMEM; @@ -2450,7 +2451,7 @@ int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids) for (i = 0; i < num_ids; i++) fwspec->ids[fwspec->num_ids + i] = ids[i]; - fwspec->num_ids += num_ids; + fwspec->num_ids = new_num; return 0; } EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids); diff --git a/include/linux/iommu.h b/include/linux/iommu.h index d1b5f4d98569d..4d1ba76c9a642 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -592,7 +592,7 @@ struct iommu_fwspec { u32 flags; u32 num_pasid_bits; unsigned int num_ids; - u32 ids[1]; + u32 ids[]; }; /* ATS is supported */ -- 2.30.2