[PATCH for_v22] selftests/x86/sgx: Ensure SECS base (ELRANGE) is naturally aligned

[Sean Christopherson <sean.j.christopherson@xxxxxxxxx>]

Manually align ELRANGE now that the kernel doesn't automatically do so
for SGX mappings.  To guarantee mmap() returns a region that can be
naturally aligned, temporarily map 2x the enclave size and do fancy
arithmetic to naturally align the base.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 tools/testing/selftests/x86/sgx/main.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/x86/sgx/main.c b/tools/testing/selftests/x86/sgx/main.c
index effcdb3380ad..5bbc60cf7f89 100644
--- a/tools/testing/selftests/x86/sgx/main.c
+++ b/tools/testing/selftests/x86/sgx/main.c
@@ -130,7 +130,8 @@ static bool encl_create(int dev_fd, unsigned long bin_size,
 			struct sgx_secs *secs)
 {
 	struct sgx_enclave_create ioc;
-	void *base;
+	uint64_t base;
+	void *basep;
 	int rc;
 
 	memset(secs, 0, sizeof(*secs));
@@ -141,19 +142,27 @@ static bool encl_create(int dev_fd, unsigned long bin_size,
 	for (secs->size = 4096; secs->size < bin_size; )
 		secs->size <<= 1;
 
-	base = mmap(NULL, secs->size, PROT_NONE, MAP_SHARED, dev_fd, 0);
-	if (base == MAP_FAILED) {
+	basep = mmap(NULL, secs->size * 2, PROT_NONE, MAP_SHARED, dev_fd, 0);
+	if (basep == MAP_FAILED) {
 		perror("mmap");
 		return false;
 	}
+	base = (uint64_t)basep;
 
-	secs->base = (uint64_t)base;
+	secs->base = base + secs->size - (base % secs->size);
+
+	if (secs->base != base)
+		munmap(basep, secs->base - base);
+
+	if (secs->base - secs->size != base)
+		munmap((void *)(secs->base + secs->size),
+		       base + secs->size - secs->base);
 
 	ioc.src = (unsigned long)secs;
 	rc = ioctl(dev_fd, SGX_IOC_ENCLAVE_CREATE, &ioc);
 	if (rc) {
 		fprintf(stderr, "ECREATE failed rc=%d, err=%d.\n", rc, errno);
-		munmap(base, secs->size);
+		munmap((void *)secs->base, secs->size);
 		return false;
 	}
 
-- 
2.22.0