added nasm

nasm/README.md

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+# Netwide Assembler
+
+This is the (Nasm) Netwide assembler and it is meant to be used in the binary compatibility mode of Unikraft.
+
+## Content
+
+- `sample_code.s`: a sample assembly code file that can be assembled using Nasm
+- `usr/bin/nasm`: the Nasm binary
+- `lib/` & `lib64/`: the required libraries for Nasm
+
+## Extract Dynamic Libraries
+
+```console
+../extract.sh usr/bin/nasm
+```
+
+output:
+
+```
+Copying /lib/x86_64-linux-gnu/libc.so.6 ...
+Copying /lib64/ld-linux-x86-64.so.2 ...
+```
+
+## Run on Linux
+
+```console
+nasm sample_code.s
+```
+
+## Run on Unikraft
+
+```console
+./run.sh -r ../dynamic-apps/nasm/ usr/bin/nasm sample_code.s
+```
+
+This should generate the output file `sample_code` which is the assembled machine code generated by Nasm.
+
+We can use this command to check that everything worked properly:
+
+```console
+objdump -D -b binary -m i386 -M intel,x86-64 sample_code
+```
+

nasm/sample_code.s

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+BITS 64
+
+xor rax, rax
+test rdi, rdi
+jz end
+
+loop:
+cmp byte [rdi], 0
+jz end
+
+xor rbx, rbx
+mov bl, byte [rdi]
+cmp bl, 0x5a
+ja loop_end
+
+push rax
+push rdi
+mov rdi, rbx
+mov rax, 0x403000
+call rax
+pop rdi
+mov byte [rdi], al
+pop rax
+inc rax
+
+loop_end:
+inc rdi
+jmp loop
+
+end:
+ret