On Tue, Feb 02, 2021 at 11:47:19AM -0800, ira.weiny@xxxxxxxxx wrote: > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > kmap is inefficient and we are trying to reduce the usage in the kernel. > There is no readily apparent reason why initp_page needs to be allocated > and kmap'ed() but sigstruct needs to be page aligned and token > 512 byte aligned. > > kmalloc() can give us this alignment but we need to allocate PAGE_SIZE > bytes to do so. Rather than change this kmap() to kmap_local_page() use > kmalloc() instead. > > Remove the alloc_page()/kmap() and replace with kmalloc() to get a > kernel address to use. > > In addition add a comment to document the alignment requirements so that > others like myself don't attempt to 'fix' this again. Finally, add 2 > BUILD_BUG_ON's to ensure future changes to sigstruct and token do not go > unnoticed and cause a bug. > > Cc: Dave Hansen <dave.hansen@xxxxxxxxx> > Cc: Sean Christopherson <seanjc@xxxxxxxxxx> > Cc: Jethro Beekman <jethro@xxxxxxxxxxxx> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > --- > Changes from v2[1]: > When allocating a power of 2 size kmalloc() now guarantees the > alignment of the respective size. So go back to using kmalloc() but > with a PAGE_SIZE allocation to get the alignment. This also follows > the pattern in sgx_ioc_enclave_create() > > Changes from v1[1]: > Use page_address() instead of kcmalloc() to ensure sigstruct is > page aligned > Use BUILD_BUG_ON to ensure token and sigstruct don't collide. > > [1] https://lore.kernel.org/lkml/20210129001459.1538805-1-ira.weiny@xxxxxxxxx/ > [2] https://lore.kernel.org/lkml/20210202013725.3514671-1-ira.weiny@xxxxxxxxx/ > --- > arch/x86/kernel/cpu/sgx/ioctl.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > index 90a5caf76939..e0c3301ccd67 100644 > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > @@ -604,7 +604,6 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg) > { > struct sgx_sigstruct *sigstruct; > struct sgx_enclave_init init_arg; > - struct page *initp_page; > void *token; > int ret; > > @@ -615,11 +614,16 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg) > if (copy_from_user(&init_arg, arg, sizeof(init_arg))) > return -EFAULT; > > - initp_page = alloc_page(GFP_KERNEL); > - if (!initp_page) > + /* > + * sigstruct must be on a page boundry and token on a 512 byte boundry > + * kmalloc() gives us this alignment when allocating PAGE_SIZE bytes > + */ > + sigstruct = kmalloc(PAGE_SIZE, GFP_KERNEL); > + if (!sigstruct) > return -ENOMEM; > > - sigstruct = kmap(initp_page); > + BUILD_BUG_ON(sizeof(*sigstruct) > (PAGE_SIZE/2)); > + BUILD_BUG_ON(SGX_LAUNCH_TOKEN_SIZE > (PAGE_SIZE/2)); Please remove these. > token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2); > memset(token, 0, SGX_LAUNCH_TOKEN_SIZE); > > @@ -645,8 +649,7 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg) > ret = sgx_encl_init(encl, sigstruct, token); > > out: > - kunmap(initp_page); > - __free_page(initp_page); > + kfree(sigstruct); > return ret; > } > > -- > 2.28.0.rc0.12.gb6a658bd00c9 > > /Jarkko
