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. Link: https://lore.kernel.org/all/f9c24d89-ed72-7d9e-c650-050d722c6...@cs.kuleuven.be/ Signed-off-by: Jo Van Bulck <jo.vanbu...@cs.kuleuven.be> Reviewed-by: Jarkko Sakkinen <jar...@kernel.org> Acked-by: Kai Huang <kai.hu...@intel.com> --- tools/testing/selftests/sgx/Makefile | 2 +- tools/testing/selftests/sgx/test_encl.lds | 1 + tools/testing/selftests/sgx/test_encl_bootstrap.S | 9 ++++++--- 3 files changed, 8 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/sgx/Makefile b/tools/testing/selftests/sgx/Makefile index 7eb890bdd3f0..8d2ba6adc92b 100644 --- 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 a1ec64f7d91f..62d37160f59b 100644 --- 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 e0ce993d3f2c..28fe5d2ac0af 100644 --- 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 -- 2.25.1
