Do relocation for .rela.dyn section

src/libos/src/elf_helper.rs

@@ -34,15 +34,15 @@ pub fn print_sections(elf_file: &ElfFile) -> Result<(), Error> {
     Ok(())
 }
 
-pub fn print_pltrel_section(elf_file: &ElfFile) -> Result<(), Error> {
+pub fn print_rela_plt_section(elf_file: &ElfFile) -> Result<(), Error> {
-    let rela_entries = get_pltrel_entries(elf_file)
+    let rela_entries = get_rela_entries(elf_file, ".rela.plt")
         .map_err(|e| (Errno::ENOEXEC,
                       "Failed to get .pltrel entries"))?;
     let dynsym_entries = get_dynsym_entries(elf_file)
         .map_err(|e| (Errno::ENOEXEC,
                       "Failed to get .dynsym entries"))?;
 
-    println!(".plt.rela section:");
+    println!(".rela.plt section:");
     for entry in rela_entries {
         println!("\toffset: {}, symbol index: {}, type: {}, addend: {}",
                  entry.get_offset(),
@@ -113,10 +113,10 @@ pub fn get_sym_entries<'b, 'a: 'b>(elf_file: &'b ElfFile<'a>)
         }).ok_or_else(|| (Errno::ENOEXEC, "Failed get the symbol entries").into())
 }
 
-pub fn get_pltrel_entries<'b, 'a: 'b>(elf_file: &'b ElfFile<'a>)
+pub fn get_rela_entries<'b, 'a: 'b>(elf_file: &'b ElfFile<'a>, sec_name: &'b str)
     -> Result<&'a [Rela<P64>], Error>
 {
-    elf_file.find_section_by_name(".rela.plt")
+    elf_file.find_section_by_name(sec_name)
         .and_then(|plt_rela_section| {
             plt_rela_section.get_data(&elf_file).ok()
         }).and_then(|rela_table| {

src/libos/src/process.rs

@@ -232,8 +232,10 @@ impl Process {
     {
         let mut new_process : Process = Default::default();
         new_process.create_process_image(elf_file)?;
+        new_process.reloc_symbols(elf_file)?;
         new_process.link_syscalls(elf_file)?;
         new_process.mprotect()?;
+        //println!("Process image: {:#X?}", new_process);
 
         new_process.task = Task {
             user_stack_addr: new_process.init_stack(argv, envp)? as usize,
@@ -298,12 +300,41 @@ impl Process {
         Ok(base_addr)
     }
 
+    fn reloc_symbols(self: &mut Process, elf_file: &ElfFile)
+        -> Result<(), Error>
+    {
+        let rela_entries = elf_helper::get_rela_entries(&elf_file, ".rela.dyn")?;
+        for rela_entry in rela_entries {
+            /*
+            println!("\toffset: {:#X}, symbol index: {}, type: {}, addend: {:#X}",
+                 rela_entry.get_offset(),
+                 rela_entry.get_symbol_table_index(),
+                 rela_entry.get_type(),
+                 rela_entry.get_addend());
+            */
+
+            /* reloc type == R_X86_64_RELATIVE */
+            match rela_entry.get_type() {
+                8 if rela_entry.get_symbol_table_index() == 0 => {
+                    let rela_addr = self.program_base_addr + rela_entry.get_offset() as usize;
+                    let rela_val = self.program_base_addr + rela_entry.get_addend() as usize;
+                    unsafe {
+                        std::ptr::write_unaligned(rela_addr as *mut usize, rela_val);
+                    }
+                }
+                // TODO: need to handle other relocation types
+                _ => {  }
+            }
+        }
+        Ok(())
+    }
+
     fn link_syscalls(self: &mut Process, elf_file: &ElfFile)
         -> Result<(), Error>
     {
         let syscall_addr = __occlum_syscall as *const () as usize;
 
-        let rela_entries = elf_helper::get_pltrel_entries(&elf_file)?;
+        let rela_entries = elf_helper::get_rela_entries(&elf_file, ".rela.plt")?;
         let dynsym_entries = elf_helper::get_dynsym_entries(&elf_file)?;
         for rela_entry in rela_entries {
             let dynsym_idx = rela_entry.get_symbol_table_index() as usize;

test/Makefile

@@ -1,7 +1,7 @@
 CUR_DIR := $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
 PROJECT_DIR := $(realpath $(CUR_DIR)/../)
 
-TEST_SUITES := empty
+TEST_SUITES := empty hello_world
 BUILD_TEST_SUITES := $(TEST_SUITES:%=%)
 RUN_TEST_SUITES := $(TEST_SUITES:%=run-%)
 CLEAN_TEST_SUITES := $(TEST_SUITES:%=clean-%)

test/hello_world/Makefile

@@ -0,0 +1,4 @@
+include ../test_common.mk
+
+EXTRA_C_FLAGS :=
+EXTRA_LINK_FLAGS :=

test/hello_world/main.c

@@ -0,0 +1,9 @@
+#include <unistd.h>
+#include <string.h>
+
+static const char* msg = "Hello World\n";
+
+int main(void) {
+    write(1, msg, strlen(msg) + 1);
+    return 0;
+}