[RFC 04/12] x86/mm: Add helper functions to manage memory encryption keys

[Huang, Kai]

> -----Original Message-----
> From: owner-linux-security-module at vger.kernel.org [mailto:owner-linux-
> security-module at vger.kernel.org] On Behalf Of Alison Schofield
> Sent: Saturday, September 8, 2018 10:36 AM
> To: dhowells at redhat.com; tglx at linutronix.de
> Cc: Huang, Kai <kai.huang at intel.com>; Nakajima, Jun
> <jun.nakajima at intel.com>; Shutemov, Kirill <kirill.shutemov at intel.com>;
> Hansen, Dave <dave.hansen at intel.com>; Sakkinen, Jarkko
> <jarkko.sakkinen at intel.com>; jmorris at namei.org; keyrings at vger.kernel.org;
> linux-security-module at vger.kernel.org; mingo at redhat.com; hpa at zytor.com;
> x86 at kernel.org; linux-mm at kvack.org
> Subject: [RFC 04/12] x86/mm: Add helper functions to manage memory
> encryption keys
> 
> Define a global mapping structure to track the mapping of userspace keys to
> hardware keyids in MKTME (Multi-Key Total Memory Encryption).
> This data will be used for the memory encryption system call and the kernel key
> service API.
> 
> Implement helper functions to access this mapping structure and make them
> visible to the MKTME Kernel Key Service: security/keys/mktme_keys
> 
> Signed-off-by: Alison Schofield <alison.schofield at intel.com>
> ---
>  arch/x86/include/asm/mktme.h | 11 ++++++
>  arch/x86/mm/mktme.c          | 85
> ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 96 insertions(+)

Maybe it's better to put those changes to include/keys/mktme-type.h, and security/keys/mktme_key.c? It seems you don't have to involve linux-mm and x86 guys by doing so?

Thanks,
-Kai
> 
> diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
> index dbfbd955da98..f6acd551457f 100644
> --- a/arch/x86/include/asm/mktme.h
> +++ b/arch/x86/include/asm/mktme.h
> @@ -13,6 +13,17 @@ extern phys_addr_t mktme_keyid_mask;  extern int
> mktme_nr_keyids;  extern int mktme_keyid_shift;
> 
> +/* Manage mappings between hardware keyids and userspace keys */ extern
> +int mktme_map_alloc(void); extern void mktme_map_free(void); extern
> +void mktme_map_lock(void); extern void mktme_map_unlock(void); extern
> +int mktme_map_get_free_keyid(void); extern void
> +mktme_map_clear_keyid(int keyid); extern void mktme_map_set_keyid(int
> +keyid, unsigned int serial); extern int
> +mktme_map_keyid_from_serial(unsigned int serial); extern unsigned int
> +mktme_map_serial_from_keyid(int keyid);
> +
>  extern struct page_ext_operations page_mktme_ops;
> 
>  #define page_keyid page_keyid
> diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c index
> 660caf6a5ce1..5246d8323359 100644
> --- a/arch/x86/mm/mktme.c
> +++ b/arch/x86/mm/mktme.c
> @@ -63,6 +63,91 @@ int vma_keyid(struct vm_area_struct *vma)
>  	return (prot & mktme_keyid_mask) >> mktme_keyid_shift;  }
> 
> +/*
> + * struct mktme_mapping and the mktme_map_* functions manage the
> +mapping
> + * of userspace keys to hardware keyids in MKTME. They are used by the
> + * the encrypt_mprotect system call and the MKTME Key Service API.
> + */
> +struct mktme_mapping {
> +	struct mutex	lock;		/* protect this map & HW state */
> +	unsigned int	mapped_keyids;
> +	unsigned int	serial[];
> +};
> +
> +struct mktme_mapping *mktme_map;
> +
> +static inline long mktme_map_size(void) {
> +	long size = 0;
> +
> +	size += sizeof(mktme_map);
> +	size += sizeof(mktme_map->serial[0]) * mktme_nr_keyids;
> +	return size;
> +}
> +
> +int mktme_map_alloc(void)
> +{
> +	mktme_map = kzalloc(mktme_map_size(), GFP_KERNEL);
> +	if (!mktme_map)
> +		return 0;
> +	mutex_init(&mktme_map->lock);
> +	return 1;
> +}
> +
> +void mktme_map_free(void)
> +{
> +	kfree(mktme_map);
> +}
> +
> +void mktme_map_lock(void)
> +{
> +	mutex_lock(&mktme_map->lock);
> +}
> +
> +void mktme_map_unlock(void)
> +{
> +	mutex_unlock(&mktme_map->lock);
> +}
> +
> +void mktme_map_set_keyid(int keyid, unsigned int serial) {
> +	mktme_map->serial[keyid] = serial;
> +	mktme_map->mapped_keyids++;
> +}
> +
> +void mktme_map_clear_keyid(int keyid)
> +{
> +	mktme_map->serial[keyid] = 0;
> +	mktme_map->mapped_keyids--;
> +}
> +
> +unsigned int mktme_map_serial_from_keyid(int keyid) {
> +	return mktme_map->serial[keyid];
> +}
> +
> +int mktme_map_keyid_from_serial(unsigned int serial) {
> +	int i;
> +
> +	for (i = 1; i < mktme_nr_keyids; i++)
> +		if (mktme_map->serial[i] == serial)
> +			return i;
> +	return 0;
> +}
> +
> +int mktme_map_get_free_keyid(void)
> +{
> +	int i;
> +
> +	if (mktme_map->mapped_keyids < mktme_nr_keyids) {
> +		for (i = 1; i < mktme_nr_keyids; i++)
> +			if (mktme_map->serial[i] == 0)
> +				return i;
> +	}
> +	return 0;
> +}
> +
>  void prep_encrypted_page(struct page *page, int order, int keyid, bool zero)  {
>  	int i;
> --
> 2.14.1