Auto merge of #67084 - Pagten:feature/print-msg-from-elf-entrypoint, r=Amanieu
SGX: Change ELF entrypoint
This fixes [rust-sgx issue #148](https://github.com/fortanix/rust-sgx/issues/148).
A new entry point is created for the ELF file generated by `rustc`, separate from the enclave entry point. When the ELF file is executed as a Linux binary, the error message below is written to stderr.
> Error: This file is an SGX enclave which cannot be executed as a standard Linux binary.
> See the installation guide at https://edp.fortanix.com/docs/installation/guide/ on how to use 'cargo run' or follow the steps at https://edp.fortanix.com/docs/tasks/deployment/ for manual deployment.
When the ELF file is converted to an SGXS using `elf2sgxs`, the old entry point is still set as the enclave entry point. In a future pull request in the rust-sgx repository, `elf2sgxs` will be modified to remove the code in the ELF entry point, since this code is not needed in the enclave.
diff --git a/src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs b/src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs
index dbcd77b..2c9ba9f 100644
--- a/src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs
+++ b/src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs
@@ -7,7 +7,7 @@
"--as-needed",
"--eh-frame-hdr",
"-z" , "noexecstack",
- "-e","sgx_entry",
+ "-e","elf_entry",
"-Bstatic",
"--gc-sections",
"-z","text",
diff --git a/src/libstd/sys/sgx/abi/entry.S b/src/libstd/sys/sgx/abi/entry.S
index cd26c7c..a3e059e81 100644
--- a/src/libstd/sys/sgx/abi/entry.S
+++ b/src/libstd/sys/sgx/abi/entry.S
@@ -104,6 +104,36 @@
and %gs:tcsls_flags,%\reg
.endm
+/* We place the ELF entry point in a separate section so it can be removed by
+ elf2sgxs */
+.section .text_no_sgx, "ax"
+.Lelf_entry_error_msg:
+ .ascii "Error: This file is an SGX enclave which cannot be executed as a standard Linux binary.\nSee the installation guide at https://edp.fortanix.com/docs/installation/guide/ on how to use 'cargo run' or follow the steps at https://edp.fortanix.com/docs/tasks/deployment/ for manual deployment.\n"
+.Lelf_entry_error_msg_end:
+
+.global elf_entry
+.type elf_entry,function
+elf_entry:
+/* print error message */
+ movq $2,%rdi /* write to stderr (fd 2) */
+ lea .Lelf_entry_error_msg(%rip),%rsi
+ movq $.Lelf_entry_error_msg_end-.Lelf_entry_error_msg,%rdx
+.Lelf_entry_call:
+ movq $1,%rax /* write() syscall */
+ syscall
+ test %rax,%rax
+ jle .Lelf_exit /* exit on error */
+ add %rax,%rsi
+ sub %rax,%rdx /* all chars written? */
+ jnz .Lelf_entry_call
+
+.Lelf_exit:
+ movq $60,%rax /* exit() syscall */
+ movq $1,%rdi /* exit code 1 */
+ syscall
+ ud2 /* should not be reached */
+/* end elf_entry */
+
.text
.global sgx_entry
.type sgx_entry,function
