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-rw-r--r--arch/x86/kernel/cpu/sgx/encl.c57
1 files changed, 48 insertions, 9 deletions
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 48afe96ae0f0..7c63a1911fae 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -13,6 +13,30 @@
#include "sgx.h"
/*
+ * Calculate byte offset of a PCMD struct associated with an enclave page. PCMD's
+ * follow right after the EPC data in the backing storage. In addition to the
+ * visible enclave pages, there's one extra page slot for SECS, before PCMD
+ * structs.
+ */
+static inline pgoff_t sgx_encl_get_backing_page_pcmd_offset(struct sgx_encl *encl,
+ unsigned long page_index)
+{
+ pgoff_t epc_end_off = encl->size + sizeof(struct sgx_secs);
+
+ return epc_end_off + page_index * sizeof(struct sgx_pcmd);
+}
+
+/*
+ * Free a page from the backing storage in the given page index.
+ */
+static inline void sgx_encl_truncate_backing_page(struct sgx_encl *encl, unsigned long page_index)
+{
+ struct inode *inode = file_inode(encl->backing);
+
+ shmem_truncate_range(inode, PFN_PHYS(page_index), PFN_PHYS(page_index) + PAGE_SIZE - 1);
+}
+
+/*
* ELDU: Load an EPC page as unblocked. For more info, see "OS Management of EPC
* Pages" in the SDM.
*/
@@ -22,9 +46,11 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
{
unsigned long va_offset = encl_page->desc & SGX_ENCL_PAGE_VA_OFFSET_MASK;
struct sgx_encl *encl = encl_page->encl;
+ pgoff_t page_index, page_pcmd_off;
struct sgx_pageinfo pginfo;
struct sgx_backing b;
- pgoff_t page_index;
+ bool pcmd_page_empty;
+ u8 *pcmd_page;
int ret;
if (secs_page)
@@ -32,14 +58,16 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
else
page_index = PFN_DOWN(encl->size);
+ page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);
+
ret = sgx_encl_get_backing(encl, page_index, &b);
if (ret)
return ret;
pginfo.addr = encl_page->desc & PAGE_MASK;
pginfo.contents = (unsigned long)kmap_atomic(b.contents);
- pginfo.metadata = (unsigned long)kmap_atomic(b.pcmd) +
- b.pcmd_offset;
+ pcmd_page = kmap_atomic(b.pcmd);
+ pginfo.metadata = (unsigned long)pcmd_page + b.pcmd_offset;
if (secs_page)
pginfo.secs = (u64)sgx_get_epc_virt_addr(secs_page);
@@ -55,11 +83,24 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
ret = -EFAULT;
}
- kunmap_atomic((void *)(unsigned long)(pginfo.metadata - b.pcmd_offset));
+ memset(pcmd_page + b.pcmd_offset, 0, sizeof(struct sgx_pcmd));
+
+ /*
+ * The area for the PCMD in the page was zeroed above. Check if the
+ * whole page is now empty meaning that all PCMD's have been zeroed:
+ */
+ pcmd_page_empty = !memchr_inv(pcmd_page, 0, PAGE_SIZE);
+
+ kunmap_atomic(pcmd_page);
kunmap_atomic((void *)(unsigned long)pginfo.contents);
sgx_encl_put_backing(&b, false);
+ sgx_encl_truncate_backing_page(encl, page_index);
+
+ if (pcmd_page_empty)
+ sgx_encl_truncate_backing_page(encl, PFN_DOWN(page_pcmd_off));
+
return ret;
}
@@ -579,7 +620,7 @@ static struct page *sgx_encl_get_backing_page(struct sgx_encl *encl,
int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
struct sgx_backing *backing)
{
- pgoff_t pcmd_index = PFN_DOWN(encl->size) + 1 + (page_index >> 5);
+ pgoff_t page_pcmd_off = sgx_encl_get_backing_page_pcmd_offset(encl, page_index);
struct page *contents;
struct page *pcmd;
@@ -587,7 +628,7 @@ int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
if (IS_ERR(contents))
return PTR_ERR(contents);
- pcmd = sgx_encl_get_backing_page(encl, pcmd_index);
+ pcmd = sgx_encl_get_backing_page(encl, PFN_DOWN(page_pcmd_off));
if (IS_ERR(pcmd)) {
put_page(contents);
return PTR_ERR(pcmd);
@@ -596,9 +637,7 @@ int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
backing->page_index = page_index;
backing->contents = contents;
backing->pcmd = pcmd;
- backing->pcmd_offset =
- (page_index & (PAGE_SIZE / sizeof(struct sgx_pcmd) - 1)) *
- sizeof(struct sgx_pcmd);
+ backing->pcmd_offset = page_pcmd_off & (PAGE_SIZE - 1);
return 0;
}