selftests/sgx: Produce static-pie executable for test enclave

The current combination of -static and -fPIC creates a static executable
with position-dependent addresses for global variables. Use -static-pie
and -fPIE to create a proper static position independent executable that
can be loaded at any address without a dynamic linker.

When building the original "lea (encl_stack)(%rbx), %rax" assembly code
with -static-pie -fPIE, the linker complains about a relocation it cannot
resolve:

/usr/local/bin/ld: /tmp/cchIWyfG.o: relocation R_X86_64_32S against
`.data' can not be used when making a PIE object; recompile with -fPIE
collect2: error: ld returned 1 exit status

Thus, since only RIP-relative addressing is legit for local symbols, use
"encl_stack(%rip)" and declare an explicit "__encl_base" symbol at the
start of the linker script to be able to calculate the stack address
relative to the current TCS in the enclave assembly entry code.

Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/f9c24d89-ed72-7d9e-c650-050d722c6b04@cs.kuleuven.be/
Link: https://lore.kernel.org/all/20231005153854.25566-8-jo.vanbulck%40cs.kuleuven.be

diff --git a/tools/testing/selftests/sgx/Makefile b/tools/testing/selftests/sgx/Makefile
index 7eb890bdd3f0c0c033706da603bb1d0ef1c53b50..8d2ba6adc92bd5f45f33f4c74ecdda00efbbf04a 100644 (file)
--- a/tools/testing/selftests/sgx/Makefile
+++ b/tools/testing/selftests/sgx/Makefile
@@ -14,7 +14,7 @@ endif
 INCLUDES := -I$(top_srcdir)/tools/include
 HOST_CFLAGS := -Wall -Werror -g $(INCLUDES) -fPIC
 HOST_LDFLAGS := -z noexecstack -lcrypto
-ENCL_CFLAGS += -Wall -Werror -static -nostdlib -ffreestanding -fPIC \
+ENCL_CFLAGS += -Wall -Werror -static-pie -nostdlib -ffreestanding -fPIE \
               -fno-stack-protector -mrdrnd $(INCLUDES)
 ENCL_LDFLAGS := -Wl,-T,test_encl.lds,--build-id=none
 

diff --git a/tools/testing/selftests/sgx/test_encl.lds b/tools/testing/selftests/sgx/test_encl.lds
index a1ec64f7d91fc52bc8a8971fd64f261790a73cf1..62d37160f59b2b2b4660a89914009efbce006056 100644 (file)
--- a/tools/testing/selftests/sgx/test_encl.lds
+++ b/tools/testing/selftests/sgx/test_encl.lds
@@ -10,6 +10,7 @@ PHDRS
 SECTIONS
 {
        . = 0;
+        __encl_base = .;
        .tcs : {
                *(.tcs*)
        } : tcs

diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
index e0ce993d3f2cb5004b308e76844bbee36b361e6f..28fe5d2ac0afd95fe66c1e51e407783e86e32e75 100644 (file)
--- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
+++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
@@ -42,9 +42,12 @@
 encl_entry:
        # RBX contains the base address for TCS, which is the first address
        # inside the enclave for TCS #1 and one page into the enclave for
-       # TCS #2. By adding the value of encl_stack to it, we get
-       # the absolute address for the stack.
-       lea     (encl_stack)(%rbx), %rax
+       # TCS #2. First make it relative by substracting __encl_base and
+       # then add the address of encl_stack to get the address for the stack.
+       lea __encl_base(%rip), %rax
+       sub %rax, %rbx
+       lea encl_stack(%rip), %rax
+       add %rbx, %rax
        jmp encl_entry_core
 encl_dyn_entry:
        # Entry point for dynamically created TCS page expected to follow