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    SubjectRe: [PATCH v4 02/13] selftests/sgx: Produce static-pie executable for test enclave
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    On Fri, 2023-08-25 at 15:32 +0200, Jo Van Bulck wrote:
    > 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.
    >
    > Link: https://lore.kernel.org/all/f9c24d89-ed72-7d9e-c650-050d722c6b04@cs.kuleuven.be/
    > Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
    > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
    > ---
    > 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 50aab6b57da3..1d6315a2e5f5 100644
    > --- a/tools/testing/selftests/sgx/Makefile
    > +++ b/tools/testing/selftests/sgx/Makefile
    > @@ -13,7 +13,7 @@ endif
    >
    > INCLUDES := -I$(top_srcdir)/tools/include
    > HOST_CFLAGS := -Wall -Werror -g $(INCLUDES) -fPIC -z noexecstack
    > -ENCL_CFLAGS := -Wall -Werror -static -nostdlib -nostartfiles -fPIC \
    > +ENCL_CFLAGS := -Wall -Werror -static-pie -nostdlib -nostartfiles -fPIE \
    > -fno-stack-protector -mrdrnd $(INCLUDES)
    >
    > TEST_CUSTOM_PROGS := $(OUTPUT)/test_sgx
    > 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 03ae0f57e29d..4e55d91566c4 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

    Could you please add the linker error (as you mentioned in the v3) to the
    changelog to justify this code change?

    And sigh.. I still don't quite understand why linker complains

    lea (encl_stack)(%rbx), %rax

    because ....

    > jmp encl_entry_core
    > encl_dyn_entry:
    > # Entry point for dynamically created TCS page expected to follow

    we have a

    lea -1(%rbx), %rax

    right here.

    Can't the compiler/linker just treat it as an immediate just like -1? :-(

    Anyway, I like this code change:

    Acked-by: Kai Huang <kai.huang@intel.com>

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