Cleanup and noting of code to prepare it for work

5 files changed, 178 insertions, 153 deletions

diff --git a/.sh.s.swp b/.sh.s.swp
new file mode 100644
index 0000000..9c0da39
--- /dev/null
+++ b/.sh.s.swp
diff --git a/makefile b/makefile
index 04a37e8..3725a30 100644
--- a/makefile
+++ b/makefile
@@ -1,5 +1,5 @@
 all:
-	nasm sh.s -f elf64 -o sh.o
+	nasm sh.asm -f elf64 -o sh.o
 	ld sh.o -o sh
 clean:
 	rm -f sh.o sh
diff --git a/sh b/sh
new file mode 100755
index 0000000..b8aae89
--- /dev/null
+++ b/sh
diff --git a/sh.s b/sh.asm
index edc6710..123d772 100644
--- a/sh.s
+++ b/sh.asm
@@ -1,3 +1,25 @@
+section .data
+	sigs: dd 0x2
+	cpid: dd 0x0
+	eol: db `\n`
+	msg: db "Welcome to deadbeef shell", 0x21, `\n`
+	prompt: db "[0xdeadbeef]", 0x20
+	nfe: db "Error: program not found", 0x2e, `\n`
+	env: db "/etc/environment", 0x0
+	boem: db "Error: input overflows buffer", 0x2e, `\n`
+
+  ;Syscall constants
+  sys_read equ 0x00
+  sys_write equ 0x01
+  sys_open equ 0x02
+  sys_close equ 0x03
+  stub_fork equ 0x39
+  stub_execve equ 0x3b
+  sys_exit equ 0x3c
+  sys_wait4 equ 0x3d
+  sys_kill equ 0x3e
+
+
 section .text
 	global _start
 
@@ -13,376 +35,379 @@ _start:
 	sub rsp, 0x110
 	mov rbx, rsp
 
-	mov rax, 0x1
+	mov rax, sys_write
 	mov rdi, 0x1
 	mov rsi, msg
 	mov rdx, 0x1b
 	syscall
 
-	jmp parse_path
+	jmp _parse_path
 
-rloop:
-	mov rax, 0x1
+_rloop:
+	mov rax, sys_write
 	mov rdi, 0x1
 	mov rsi, prompt
 	mov rdx, 0xd
 	syscall
 
 	mov r8, -0x1
-	mov r12, rloopr
-	jmp bzero
+	mov r12, _rloopr
+	jmp _bzero
 
-rloopr:
-	mov rax, 0x0
+_rloopr:
+	mov rax, sys_read
 	mov rdi, 0x0
 	mov rsi, r15
 	mov rdx, 0xff
 	syscall
 
-	; check for quit
+	; check for _quit
+	mov r12, _quit
 	cmp byte [r15], 0x0
-	mov r12, quit
-	je weol
+	je _weol
 
-	; call parse
-	jmp parse
+	; call _parse
+	jmp _parse
 
-exec:
+_exec:
 	; fork so we don't hurt ourselves
-	mov rax, 0x39
+	mov rax, stub_fork
 	syscall
 	mov dword [cpid], eax
 	cmp dword [cpid], 0x0
-	jne wait4_it
+	jne _wait4_it
 
 	; now that we know what to execute, do so
-	mov rax, 0x3b
+	mov rax, stub_execve
 	mov rdi, r13
 	mov rsi, r14
 	mov rdx, 0x0
 	syscall
 
 	; and now kill the child process
-	jmp quit
+	jmp _quit
 
-wait4_it:
+_wait4_it:
+	;This function is obsolete, replace with 247 (sys_waitid)
 	mov rdi, rax
-	mov rax, 0x3d
+	mov rax, sys_wait4
 	xor rsi, rsi ; null status pointer
 	xor rdx, rdx
 	xor rcx, rcx ; null rusage pointer
 	syscall
 
 	mov dword [cpid], -0x1
-	jmp rloop
+	jmp _rloop
 
 ; input: none
 ; output: r9 (path elements), r10 (length)
 ; clobbered: r8, r12
 ; other: r15 (buffer)
-parse_path:
-	mov rax, 0x2
+_parse_path:
+	mov rax, sys_open
 	mov rdi, env
 	mov rsi, 0x0
 	syscall
 	cmp rax, 0x0
-	jl quit
+	jl _quit
 
 	mov r8, -0x1
-	mov r12, parse_path2
-	jmp bzero
+	mov r12, _parse_path2
+	jmp _bzero
 
-parse_path2:
+_parse_path2:
 	mov rdi, rax
-	mov rax, 0x0
+	mov rax, sys_read
 	mov rsi, r9
 	mov rdx, 0xff
 	syscall
 	cmp rax, 0x0
-	jl quit
+	jl _quit
 	mov r8, r9
 	dec r8
 
-pathfinder:
+_pathfinder:
 	inc r8
 	xor rax, rax
 	mov byte al, [r8]
-	cmp al, 0x50
-	jne pathfinder
+	cmp al, `P`
+	jne _pathfinder
 	mov byte al, [r8+1]
-	cmp al, 0x41
-	jne pathfinder
+	cmp al, `A`
+	jne _pathfinder
 	mov byte al, [r8+2]
-	cmp al, 0x54
-	jne pathfinder
+	cmp al, `T`
+	jne _pathfinder
 	mov byte al, [r8+3]
-	cmp al, 0x48
-	jne pathfinder
+	cmp al, `H`
+	jne _pathfinder
 	mov byte al, [r8+4]
-	cmp al, 0x3d
-	jne pathfinder
+	cmp al, `=`
+	jne _pathfinder
 	mov byte al, [r8+5]
-	cmp al, 0x22
-	jne pathfinder
+	cmp al, `"`
+	jne _pathfinder
 	cmp al, 0x0
-	je quit
+	je _quit
 	add r8, 0x6
 	mov r10, 0x1
 	push 0x0
 	push r8
 	dec r8
 
-pathender:
+_pathender:
 	inc r8
 	mov al, [r8]
-	cmp al, 0x3a
-	je pathender1
-	cmp al, 0x22
-	jne pathender
+	cmp al, `:`
+	je _pathender1
+	cmp al, `"`
+	jne _pathender
 	mov byte [r8], 0x0
 	mov r9, rsp
-	jmp rloop
+	jmp _rloop
 
-pathender1:
+_pathender1:
 	inc r10
 	mov byte [r8], 0x0
 	lea rcx, [r8+0x1]
 	push rcx
-	jmp pathender
+	jmp _pathender
 
+;Writes 0s in buffer r15 until r8 is 255
 ;input: r8 (iterator), r15 (buffer), r12 (return address)
 ;output: none
-bzero:
+_bzero:
 	inc r8
 	mov byte [r8+r15], 0x0
 	cmp r8, 0xff
-	jle bzero
+	jle _bzero
 	jmp r12
 
 ;input: r15 (buffer)
 ;output: r13 (path), r14 (arguments)
 ;clobbered: r8, rax, rbx, rcx
-parse: ; needs special commands: cd exit export echo eval pwd
+_parse: ; needs special commands: cd exit export eval
+	;syscall 80 is chdir, so do that first, it's easiest
+	;It takes a path string.
 	;also needs pipes (|, >, <)
 	push 0x0
 	xor r13, r13
-	jmp strlen
+	jmp _strlen
 
+;r8 holds strlen so we start at the end and parse backwards
 ; go through and sub/push
-parse1:
-	cmp byte [r8+r15], 0x20
-	je subzp
-	cmp byte [r8+r15], 0x0a
-	je subz
-	cmp byte [r8+r15], 0x2f
-	je sabsf
-	cmp byte [r8+r15], 0x2e
-	je sabsf
-
-parse1r:
+_parse1:
+	cmp byte [r15+r8], ` `
+	je _subzp
+	cmp byte [r15+r8], `\n`
+	je _subz
+	cmp byte [r15+r8], `/`
+	je _sabsf
+	cmp byte [r15+r8], `.`
+	je _sabsf
+
+;Controls the parsing of the directory, keeps parsing each bit of the dir until
+;the end of the string or directory name
+_parse1r:
 	dec r8
 	cmp r8, 0x0
-	jl parse2
-	jmp parse1
+	jl _parse2
+	jmp _parse1
 
-sabsf:
+_sabsf:
 	cmp r8, 0x1
-	jg parse1r
+	jg _parse1r
 	mov r13, 0x1
-	jmp parse1r
+	jmp _parse1r
 
-subz:
+_subz:
 	mov byte [r8+r15], 0x0
-	jmp parse1
+	jmp _parse1
 
-subzp:
+;Splits at the current position and puts the address of the argument on the stack
+_subzp:
 	mov byte [r8+r15], 0x0
 	lea rax, [r8+r15+0x1]
 	push rax
-	jmp parse1
+	jmp _parse1
 
-parse2:
+_parse2:
 	push rbx
 	mov r14, rsp
 	cmp r13, 0x0
-	jg parse7
+	jg _parse7
 	mov r8, -0x1
 
-parse3:
+_parse3:
 	inc r8
 	cmp r8, r10
-	je parse4
+	je _parse4
 	mov r13, r15
 	mov rcx, [r9+r8*8]
 	push r8
-	jmp concat
+	jmp _concat
 
-parse4: ; not found
-	mov rax, 0x1
+_parse4: ; not found
+	mov rax, sys_write
 	mov rdi, 0x1
 	mov rsi, nfe
 	mov rdx, 0x1a
 	syscall
-	jmp rloop
+	jmp _rloop
 
-parse5: ; test rbx
+; Checks that the program rbx exists before doing anything, this is hacky, slow
+; and should therefore be replaced by a version using sys_access with flag X_OK
+_parse5:
 	pop r8
 
-	mov rax, 0x2
+	mov rax, sys_open
 	mov rdi, rbx
 	xor rsi, rsi
 	xor rdx, rdx
 	syscall
 
+  ;Check if it was opened successfully to check if it exists
 	cmp rax, 0x0
-	jl parse3
-	
+	jl _parse3
+
 	mov rdi, rax
-	mov rax, 0x3
+	mov rax, sys_close
 	syscall
 
-parse6: ; found it
+; We'll fall through to here if the file is accessible, therefore we should execute it
+_parse6:
 	mov r13, rbx
-	jmp exec
+	jmp _exec
 
-parse7: ; absolute path
-	mov rax, 0x2
+_parse7: ; absolute path
+	mov rax, sys_open
 	mov rdi, r15
 	xor rsi, rsi
 	xor rdx, rdx
 	syscall
 
 	cmp rax, 0x0
-	jl parse4
+	jl _parse4
 
 	mov rdi, rax
-	mov rax, 0x3
+	mov rax, sys_close
 	syscall
 
 	mov r13, r15
-	jmp exec
-	
+	jmp _exec
+
 
 ;input: r12 (return address), r15 (buffer)
 ;output: r8 (length)
-strlen:
+_strlen:
 	xor r8, r8
 
-strlen1:
+_strlen1:
 	cmp byte [r8+r15], 0x0
-	je parse1
+	je _parse1
 	cmp byte [r8+r15], 0xa
-	je parse1
+	je _parse1
 	inc r8
-	jmp strlen1
+	jmp _strlen1
 
 ; input: rcx (a), r13 (b)
 ; output: rbx (string)
 ; clobbered: r8, r11
-concat:
+_concat:
 	mov r8, -0x1
-	jmp jlen1
+	jmp _jlen1
 
-jlen1:
+_jlen1:
 	inc r8
 	cmp byte [r8+rcx], 0x0
-	je jlen02
+	je _jlen02
 	cmp byte [r8+rcx], 0xa
-	je jlen02
-	jmp jlen1
+	je _jlen02
+	jmp _jlen1
 
-jlen02:
+_jlen02:
 	dec r8
 	mov r11, -0x1
 
-jlen2:
+_jlen2:
 	inc r8
 	inc r11
 	cmp byte [r11+r13], 0x0
-	je treg
+	je _treg
 	cmp byte [r11+r13], 0xa
-	je treg
-	jmp jlen2
+	je _treg
+	jmp _jlen2
 
-treg:
+_treg:
 	cmp r8, 0xff
-	jg boe
+	jg _boe
 	xchg r15, rbx
 	mov r8, -0x1
-	mov r12, rsinc
-	jmp bzero
+	mov r12, _jrsinc
+	jmp _bzero
 
-rsinc:
+_jrsinc:
 	xchg r15, rbx
 	mov r8, -0x1
 	mov r11, -0x1
 
-join1:
+_join1:
 	inc r8
 	cmp byte [r8+rcx], 0x0
-	je join02
+	je _join02
 	cmp byte [r8+rcx], 0xa
-	je join02
+	je _join02
 	mov al, [r8+rcx]
 	mov [r8+rbx], al
-	jmp join1
+	jmp _join1
 
-join02:
-	mov byte [r8+rbx], 0x2f
-join2:
+_join02:
+	mov byte [r8+rbx], `/`
+_join2:
 	inc r8
 	inc r11
 	cmp byte [r11+r13], 0x0
-	je parse5
-	cmp byte [r11+r13], 0xa
-	je parse5
+	je _parse5
+	cmp byte [r11+r13], `\n`
+	je _parse5
 	mov al, [r11+r13]
 	mov [r8+rbx], al
-	jmp join2
+	jmp _join2
 
-boe:
-	mov rax, 0x1
+_boe:
+	mov rax, sys_write
 	mov rdi, 0x1
 	mov rsi, boem
 	mov rdx, 0x1f
-	jmp quit
+	jmp _quit
 
 ; interrupt signal handler
-sigint:
+_sigint:
 	cmp dword [cpid], 0x0
-	jl sigint_nc
+	jl _sigint_nc
 
-sigint_c: ; kill the child
-	mov rax, 0x3e
+__sigint_c: ; kill the child
+	mov rax, sys_kill
 	mov rdi, [cpid]
 	mov rsi, 0x2
 	syscall
 
-sigint_nc:
-	mov r12, rloop
-	jmp weol
+_sigint_nc:
+	mov r12, _rloop
+	jmp _weol
 
 ; input: r12 (return address)
 ; output: none
-weol:
-	mov rax, 0x1
+; Writes end of line to the terminal
+_weol:
+	mov rax, sys_write
 	mov rdi, 0x1
 	mov rsi, eol
 	mov rdx, 0x1
 	syscall
 	jmp r12
 
-quit:
-	mov rax, 0x3c
+_quit:
+	mov rax, sys_exit
 	mov rdi, 0x0
 	syscall
-
-section .data
-	sigs: dd 0x2
-	cpid: dd 0x0
-	eol: db 0xa
-	msg: db "Welcome to deadbeef shell", 0x21, 0x0a
-	prompt: db "[0xdeadbeef]", 0x20
-	nfe: db "Error: program not found", 0x2e, 0x0a
-	env: db "/etc/environment", 0x0
-	boem: db "Error: input overflows buffer", 0x2e, 0x0a
diff --git a/sh.o b/sh.o
new file mode 100644
index 0000000..164fa55
--- /dev/null
+++ b/sh.o