This handout only mentions a small subset of the rich possibilities provided by the x86-64 instruction set and architecture. For a more complete (but still readable) introduction, consult The AMD64 Architecture Programmer's Manual When calling printf, we must set the value of register %rax to 0 before issuing the call instruction. x86-64 is very similar to its 32bit counterpart. The main difference is that the registers are wider and there are more of them. You might think this would make it easy to adapt 32bit code to run in 64ibt mode under Linux. Of course, there are a few gotchas. Linux has a completely different system call ABI under 64bit mode. 2.4.1. System Calls vs. Function Calls¶. At the level of assembly language, a system call involves executing a trap instruction. In modern x86 code, the trap instruction is syscall, which acts in a manner analogous to call.Instead of jumping to a function within the same program, though, syscall triggers a mode switch and jumps to a routine in the kernel portion of memory. • x86-64 solutions • Pertinent instructions and conventions. 2. Function Call Problems (1) Calling and returning • How does caller function . jump . to callee function? • How does callee function . jump back . to the right place in caller most-recently-executed call instruction 1. 2 Subscribe Last part in the series introducing basic assembly programming for the x64 instruction set. This part explains procedure calls using the System V AMD ABI calling conventions and push and Hence there is a difference in the implementation of calling conventions. Below is comparison of major calling conventions between these two architectures. x-86 32bit. x-86 64 bit. The registers used for system call are - %ebx, %ecx, %edx, %esi, %edi, %ebp. The registers used for system call are - %rdi, %rsi, %rdx, %r10, %r8 and %r9. This register-based parameter passing is similar to how we call functions in 64-bit x86, but using different register numbers and smaller 32-bit registers, and the Linux kernel allows the use of this convention both in 32 and 64 bit mode. "int 0x80" uses a special x86 instruction to do this called "int", short for interrupt. bit PCs are being replaced with 64-bit ones, and the underlying assembly code has changed. This Gem is an introduction to x64 assembly. No prior knowledge of x86 code is needed, although it makes the transition easier. x64 is a generic name for the 64-bit extensions to Intel‟s and AMD‟s 32-bit x86 instruction set architecture (ISA). Since particular NTDLL.dll binary can execute on all types of X86 CPUs, NTDLL has to support all of the mechanisms to perform user to kernel mode transitions. The decision as to which mechanism to use is made at run time depending on the type of CPU in the system. On x64 systems, however, NTDLL always uses the syscall instruction. On X64 Our textbook provides a simplified instruction set, which they call Y86-64, based on x86-64 for use in building a processor without getting overwhelmed by the complexity of x86-64. This page summarizes some of that information for ease of reference. 1 x86-64 vs Y86-64. x86-64 This reference is intended to be precise opcode and instruction set reference (including x86-64). Its principal aim is exact definition of instruction parameters and attributes. x86asm.net. sign-extended to 64 bits (for example, CALL . 32: e: Added: x87 FPU environment (for example, FSTENV). 14/28: er: Added: Extended-real. Only x87 FPU This reference i