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[rust] Changes needed for 'x86_64-fortanix-unknown-sgx' nightly target.
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Code is guarded via defines to enable only if 'RUST_SGX' is present.

Main logic is in libunwind/src/AddressSpace.hpp
We use 6 symbols to figure out where eh_frame / eh_frame_hdr is at runtime when loaded in an SGX enclave. (EH symbols + IMAGE base)
These are set by 'fortanix-sgx-tools'.

As notes:
- Target above at the moment uses a pre-compiled libunwind.a from forked repo.
- Goal of these changes is to use official llvm with patch.
- Changes in rust-lang to use this are planned if/when this is accepted.
- Ticket: fortanix/rust-sgx#174
- Original ported changes: llvm/llvm-project@release/5.x...fortanix:release/5.x
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AdrianCX authored and nikic committed Feb 13, 2024
1 parent bcce8fa commit b36c99c
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Showing 9 changed files with 313 additions and 7 deletions.
2 changes: 1 addition & 1 deletion libunwind/CMakeLists.txt
Original file line number Diff line number Diff line change
Expand Up @@ -251,7 +251,7 @@ if (LIBUNWIND_ENABLE_ASSERTIONS)

# On Release builds cmake automatically defines NDEBUG, so we
# explicitly undefine it:
if (NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
if ((NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG") AND (NOT RUST_SGX))
add_compile_flags(-UNDEBUG)
endif()
else()
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22 changes: 22 additions & 0 deletions libunwind/README_RUST_SGX.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
# Libunwind customizations for linking with x86_64-fortanix-unknown-sgx Rust target.

## Description
### Initial Fork
Initial Fork has been made from 5.0 release of llvm (commit: 6a075b6de4)
### Detailed Description
#### Header files that we do not include for this target
1. pthread.h
#### Library that we do not link to for this target.
1. pthread (Locks used by libunwind is provided by rust stdlib for this target)

## Building unwind for rust-sgx target
### Generate Make files:
* `cd where you want to build libunwind`
* `mkdir build`
* `cd build`
* `cmake -DCMAKE_BUILD_TYPE="RELEASE" -DRUST_SGX=1 -G "Unix Makefiles" -DLLVM_ENABLE_WARNINGS=1 -DLIBUNWIND_ENABLE_PEDANTIC=0 -DLLVM_PATH=<path/to/llvm> <path/to/libunwind>`
* `"DEBUG"` could be used instead of `"RELEASE"` to enable debug logs of libunwind.

### Build:
* `make unwind_static`
* `build/lib/` will have the built library.
5 changes: 5 additions & 0 deletions libunwind/docs/BuildingLibunwind.rst
Original file line number Diff line number Diff line change
Expand Up @@ -148,3 +148,8 @@ libunwind specific options

Path where built libunwind libraries should be installed. If a relative path,
relative to ``CMAKE_INSTALL_PREFIX``.

.. option:: LIBUNWIND_ENABLE_RUST_SGX:BOOL

**Default**: ``OFF``

27 changes: 27 additions & 0 deletions libunwind/src/AddressSpace.hpp
Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,7 @@ namespace libunwind {
// __eh_frame_hdr_start = SIZEOF(.eh_frame_hdr) > 0 ? ADDR(.eh_frame_hdr) : 0;
// __eh_frame_hdr_end = SIZEOF(.eh_frame_hdr) > 0 ? . : 0;

#if !defined(RUST_SGX)
extern char __eh_frame_start;
extern char __eh_frame_end;

Expand All @@ -102,6 +103,15 @@ extern char __eh_frame_hdr_start;
extern char __eh_frame_hdr_end;
#endif

#elif defined(RUST_SGX)
extern "C" char IMAGE_BASE;
extern "C" uint64_t EH_FRM_HDR_OFFSET;
extern "C" uint64_t EH_FRM_HDR_LEN;
extern "C" uint64_t EH_FRM_OFFSET;
extern "C" uint64_t EH_FRM_LEN;
#endif


#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)

// When statically linked on bare-metal, the symbols for the EH table are looked
Expand Down Expand Up @@ -487,6 +497,10 @@ static int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo,
#endif // defined(_LIBUNWIND_USE_DL_ITERATE_PHDR)


#if defined(RUST_SGX)
extern "C" char IMAGE_BASE;
#endif

inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
UnwindInfoSections &info) {
#ifdef __APPLE__
Expand Down Expand Up @@ -520,6 +534,8 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND) && defined(_LIBUNWIND_IS_BAREMETAL)
info.dso_base = 0;
// Bare metal is statically linked, so no need to ask the dynamic loader

#if !defined(RUST_SGX)
info.dwarf_section_length = (size_t)(&__eh_frame_end - &__eh_frame_start);
info.dwarf_section = (uintptr_t)(&__eh_frame_start);
_LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %p length %p",
Expand All @@ -530,6 +546,17 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
_LIBUNWIND_TRACE_UNWINDING("findUnwindSections: index section %p length %p",
(void *)info.dwarf_index_section, (void *)info.dwarf_index_section_length);
#endif

#elif defined(RUST_SGX)
info.dwarf_section = (uintptr_t)EH_FRM_OFFSET + (uintptr_t)(&IMAGE_BASE);
info.dwarf_section_length = (uintptr_t)EH_FRM_LEN;
#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
info.dwarf_index_section = (uintptr_t)EH_FRM_HDR_OFFSET + (uintptr_t)(&IMAGE_BASE);
info.dwarf_index_section_length = (uintptr_t)EH_FRM_HDR_LEN;
#endif

#endif

if (info.dwarf_section_length)
return true;
#elif defined(_LIBUNWIND_ARM_EHABI) && defined(_LIBUNWIND_IS_BAREMETAL)
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49 changes: 44 additions & 5 deletions libunwind/src/CMakeLists.txt
Original file line number Diff line number Diff line change
@@ -1,5 +1,9 @@
# Get sources

enable_language(C CXX ASM)

set(CMAKE_POSITION_INDEPENDENT_CODE ON)

set(LIBUNWIND_CXX_SOURCES
libunwind.cpp
Unwind-EHABI.cpp
Expand All @@ -18,9 +22,6 @@ set(LIBUNWIND_C_SOURCES
Unwind-sjlj.c
Unwind-wasm.c
)
set_source_files_properties(${LIBUNWIND_C_SOURCES}
PROPERTIES
COMPILE_FLAGS "-std=c99")

set(LIBUNWIND_ASM_SOURCES
UnwindRegistersRestore.S
Expand Down Expand Up @@ -60,6 +61,44 @@ if (MSVC_IDE)
source_group("Header Files" FILES ${LIBUNWIND_HEADERS})
endif()

if (RUST_SGX)
# Compile Flags
add_definitions(-DRUST_SGX)
add_definitions(-D__NO_STRING_INLINES)
add_definitions(-D__NO_MATH_INLINES)
add_definitions(-D_LIBUNWIND_IS_BAREMETAL)
# Can't use add_definitions because CMake will reorder these arguments
list(APPEND LIBUNWIND_COMPILE_FLAGS -U_FORTIFY_SOURCE)
list(APPEND LIBUNWIND_COMPILE_FLAGS -D_FORTIFY_SOURCE=0)

list(APPEND LIBUNWIND_COMPILE_FLAGS -fno-stack-protector)
list(APPEND LIBUNWIND_COMPILE_FLAGS -ffreestanding)
list(APPEND LIBUNWIND_COMPILE_FLAGS -fexceptions)
# Avoid too new relocation types being emitted, which might prevent linking
# on older platforms.
#
# See https://github.com/rust-lang/rust/issues/34978
if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
list(APPEND LIBUNWIND_COMPILE_FLAGS -Wa,-mrelax-relocations=no)
else()
list(APPEND LIBUNWIND_COMPILE_FLAGS)
endif()

# Sources
list(APPEND LIBUNWIND_HEADERS UnwindRustSgx.h)
list(APPEND LIBUNWIND_C_SOURCES UnwindRustSgx.c)
endif()


set_source_files_properties(${LIBUNWIND_C_SOURCES}
PROPERTIES
COMPILE_FLAGS "-std=c99")

# See add_asm_sources() in compiler-rt for explanation of this workaround.
if((APPLE AND CMAKE_VERSION VERSION_LESS 3.19) OR (MINGW AND CMAKE_VERSION VERSION_LESS 3.17))
set_source_files_properties(${LIBUNWIND_ASM_SOURCES} PROPERTIES LANGUAGE C)
endif()

set(LIBUNWIND_SOURCES
${LIBUNWIND_CXX_SOURCES}
${LIBUNWIND_C_SOURCES}
Expand All @@ -82,11 +121,11 @@ if (NOT APPLE)
add_library_flags_if(LIBUNWIND_HAS_DL_LIB dl)
endif()

if (LIBUNWIND_ENABLE_THREADS AND NOT APPLE)
if (LIBUNWIND_ENABLE_THREADS AND NOT APPLE AND (NOT RUST_SGX))
add_library_flags_if(LIBUNWIND_HAS_PTHREAD_LIB pthread)
endif()

if (LIBUNWIND_ENABLE_THREADS)
if (LIBUNWIND_ENABLE_THREADS AND (NOT RUST_SGX))
add_compile_flags_if(LIBUNWIND_WEAK_PTHREAD_LIB -DLIBUNWIND_USE_WEAK_PTHREAD=1)
endif()

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2 changes: 1 addition & 1 deletion libunwind/src/RWMutex.hpp
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@

#if defined(_WIN32)
#include <windows.h>
#elif !defined(_LIBUNWIND_HAS_NO_THREADS)
#elif !defined(_LIBUNWIND_HAS_NO_THREADS) && !defined(RUST_SGX)
#include <pthread.h>
#if defined(__ELF__) && defined(_LIBUNWIND_LINK_PTHREAD_LIB)
#pragma comment(lib, "pthread")
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125 changes: 125 additions & 0 deletions libunwind/src/UnwindRustSgx.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,125 @@
//===--------------------- UnwindRustSgx.c ----------------------------------===//
//
//// The LLVM Compiler Infrastructure
////
//// This file is dual licensed under the MIT and the University of Illinois Open
//// Source Licenses. See LICENSE.TXT for details.
////
////
////===----------------------------------------------------------------------===//

#define _GNU_SOURCE
#include <link.h>

#include <elf.h>
#include <stdarg.h>
#include <stdio.h>
#include <stddef.h>
#include "UnwindRustSgx.h"

#define max_log 256

__attribute__((weak)) struct _IO_FILE *stderr = (struct _IO_FILE *)-1;

static int vwrite_err(const char *format, va_list ap)
{
int len = 0;
#ifndef NDEBUG
char s[max_log];
s[0]='\0';
len = vsnprintf(s, max_log, format, ap);
__rust_print_err((uint8_t *)s, len);
#endif
return len;
}

static int write_err(const char *format, ...)
{
int ret;
va_list args;
va_start(args, format);
ret = vwrite_err(format, args);
va_end(args);


return ret;
}

__attribute__((weak)) int fprintf (FILE *__restrict __stream,
const char *__restrict __format, ...)
{

int ret;
if (__stream != stderr) {
write_err("Rust SGX Unwind supports only writing to stderr\n");
return -1;
} else {
va_list args;
ret = 0;
va_start(args, __format);
ret += vwrite_err(__format, args);
va_end(args);
}

return ret;
}

__attribute__((weak)) int fflush (FILE *__stream)
{
// We do not need to do anything here.
return 0;
}

__attribute__((weak)) void __assert_fail(const char * assertion,
const char * file,
unsigned int line,
const char * function)
{
write_err("%s:%d %s %s\n", file, line, function, assertion);
abort();
}

// We do not report stack over flow detected.
// Calling write_err uses more stack due to the way we have implemented it.
// With possible enabling of stack probes, we should not
// get into __stack_chk_fail() at all.
__attribute__((weak)) void __stack_chk_fail() {
abort();
}

/*
* Below are defined for all executibles compiled for
* x86_64-fortanix-unknown-sgx rust target.
* Ref: rust/src/libstd/sys/sgx/abi/entry.S
*/

struct libwu_rs_alloc_meta {
size_t alloc_size;
// Should we put a signatre guard before ptr for oob access?
unsigned char ptr[0];
};

#define META_FROM_PTR(__PTR) (struct libwu_rs_alloc_meta *) \
((unsigned char *)__PTR - offsetof(struct libwu_rs_alloc_meta, ptr))

void *libuw_malloc(size_t size)
{
struct libwu_rs_alloc_meta *meta;
size_t alloc_size = size + sizeof(struct libwu_rs_alloc_meta);
meta = (void *)__rust_c_alloc(alloc_size, sizeof(size_t));
if (!meta) {
return NULL;
}
meta->alloc_size = alloc_size;
return (void *)meta->ptr;
}

void libuw_free(void *p)
{
struct libwu_rs_alloc_meta *meta;
if (!p) {
return;
}
meta = META_FROM_PTR(p);
__rust_c_dealloc((unsigned char *)meta, meta->alloc_size, sizeof(size_t));
}
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