added chapter 03 hello dynld

1 files changed, 31 insertions, 0 deletions

diff --git a/03_hello_dynld/dynld.S b/03_hello_dynld/dynld.S
new file mode 100644
index 0000000..811fe2c
--- /dev/null
+++ b/03_hello_dynld/dynld.S
@@ -0,0 +1,31 @@
+// Copyright (c) 2021 Johannes Stoelp
+
+#if !defined(__linux__) || !defined(__x86_64__)
+#    error "Only supported in linux(x86_64)!"
+#endif
+
+#include <asm/unistd.h>
+
+.intel_syntax noprefix
+
+.section .text, "ax", @progbits
+.global dl_start
+dl_start:
+    // $rsp is guaranteed to be 16-byte aligned.
+
+    // Clear $rbp as specified by the SysV AMD64 ABI.
+    xor rbp, rbp
+
+    // Load pointer to process context prepared by execve(2) syscall as
+    // specified in the SysV AMD64 ABI.
+    // Save pointer in $rdi which is the arg0 (int/ptr) register.
+    lea rdi, [rsp]
+
+    // Stack frames must be 16-byte aligned before control is transfered to the
+    // callees entry point.
+    call dl_entry
+
+    // Call exit(1) syscall to indicate error, dl_entry should not return.
+    mov rdi, 1
+    mov rax, __NR_exit
+    syscall