[PATCH 2/2] x86: sgx_vepc: implement SGX_IOC_VEPC_REMOVE ioctl

Paolo Bonzini
2021-09-13T13:14:23Z

Windows expects all pages to be in uninitialized state on startup.
Add a ioctl that does this with EREMOVE, so that userspace can bring
the pages back to this state also when resetting the VM.
Pure userspace implementations, such as closing and reopening the device,
are racy.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/uapi/asm/sgx.h | 2 ++
arch/x86/kernel/cpu/sgx/virt.c | 36 +++++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)

diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
index 9690d6899ad9..f79d84ce8033 100644
--- a/arch/x86/include/uapi/asm/sgx.h
+++ b/arch/x86/include/uapi/asm/sgx.h
@@ -27,6 +27,8 @@ enum sgx_page_flags {
_IOW(SGX_MAGIC, 0x02, struct sgx_enclave_init)
#define SGX_IOC_ENCLAVE_PROVISION \
_IOW(SGX_MAGIC, 0x03, struct sgx_enclave_provision)
+#define SGX_IOC_VEPC_REMOVE \
+ _IO(SGX_MAGIC, 0x04)

/**
* struct sgx_enclave_create - parameter structure for the
diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
index 59b9c13121cd..81dc186fda2e 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -154,6 +154,24 @@ static int sgx_vepc_free_page(struct sgx_epc_page *epc_page)
return 0;
}

+static long sgx_vepc_remove_all(struct sgx_vepc *vepc)
+{
+ struct sgx_epc_page *entry;
+ unsigned long index;
+ long failures = 0;
+
+ xa_for_each(&vepc->page_array, index, entry)
+ if (sgx_vepc_remove_page(entry))
+ failures++;
+
+ /*
+ * Return the number of pages that failed to be removed, so
+ * userspace knows that there are still SECS pages lying
+ * around.
+ */
+ return failures;
+}
+
static int sgx_vepc_release(struct inode *inode, struct file *file)
{
struct sgx_vepc *vepc = file->private_data;
@@ -239,9 +257,27 @@ static int sgx_vepc_open(struct inode *inode, struct file *file)
return 0;
}

+static long sgx_vepc_ioctl(struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ struct sgx_vepc *vepc = file->private_data;
+
+ switch (cmd) {
+ case SGX_IOC_VEPC_REMOVE:
+ if (arg)
+ return -EINVAL;
+ return sgx_vepc_remove_all(vepc);
+
+ default:
+ return -ENOTTY;
+ }
+}
+
static const struct file_operations sgx_vepc_fops = {
.owner = THIS_MODULE,
.open = sgx_vepc_open,
+ .unlocked_ioctl = sgx_vepc_ioctl,
+ .compat_ioctl = sgx_vepc_ioctl,
.release = sgx_vepc_release,
.mmap = sgx_vepc_mmap,
};
--
2.27.0