Support data in the pico mode

Makefile

@@ -1,5 +1,5 @@
-server: main.o func.o
+server: link.ld main.o func.o
-	gcc main.o func.o -o server -nostdlib -static
+	gcc -T link.ld main.o func.o -o server -nostdlib -static
 
 main.o: main.S
 	gcc -c main.S

func.S

@@ -13,7 +13,7 @@
 #define	AF_INET	PF_INET
 #define 	SOCK_STREAM	1
 
-.data
+.section .rodata
 errstr: .ascii "error happened\n"
 .set errstr_len, .-errstr
 

link.ld

@@ -0,0 +1,18 @@
+ENTRY(_start)
+
+SECTIONS {
+	. = 4M;
+	. = . + SIZEOF_HEADERS;
+	.text : { *(.text) } :text
+	.rodata : { *(.rodata) } :text
+	. += 4K;
+	.data : { *(.data) } :data
+	. = ALIGN(4K);
+	.bss : { *(COMMON) *(.bss) } :bss
+}
+
+PHDRS {
+	text PT_LOAD FILEHDR PHDRS FLAGS(5);
+	data PT_LOAD FLAGS(6);
+	bss PT_LOAD;
+}

main.S

@@ -14,7 +14,7 @@
 
 #define	PORT	20335
 
-.data
+.section .rodata
 greeting:
 	.ascii	"Welcome to the minimalistic echo server!\n"
 	.ascii	"It is written in pure assembly, and it don't use the standard library, only raw system calls.\n"
@@ -29,9 +29,6 @@ message: .ascii "Client connected\n"
 errstr: .ascii "Error happened\n"
 .set errstr_len, .-errstr
 
-s:	.quad	0
-s2:	.quad	0
-
 true_val:		.quad	1
 .set true_val_len, .-true_val
 
@@ -44,6 +41,9 @@ myaddr:
 .extern passthru
 .extern write_buf
 
+#define server_socket %rbx
+#define connection_socket %r12
+
 .text
 .global _start
 _start:
@@ -59,10 +59,10 @@ _start:
 	syscall
 	cmp $-1, %rax
 	jz error
-	movq %rax, s
+	movq %rax, server_socket
 
 	movq $__NR_setsockopt, %rax
-	movq s, %rdi
+	movq server_socket, %rdi
 	movq $SOL_SOCKET, %rsi
 	movq $SO_REUSEADDR, %rdx
 	movq $true_val, %r10
@@ -72,7 +72,7 @@ _start:
 	jnz error
 
 	movq $__NR_bind, %rax
-	movq s, %rdi
+	movq server_socket, %rdi
 	movq $myaddr, %rsi
 	movq $myaddr_len, %rdx
 	syscall
@@ -80,7 +80,7 @@ _start:
 	jnz error
 
 	movq $__NR_listen, %rax
-	movq s, %rdi
+	movq server_socket, %rdi
 	movq $8, %rsi
 	syscall
 	test %rax, %rax
@@ -88,14 +88,14 @@ _start:
 
 loop:
 	movq $__NR_accept, %rax
-	movq s, %rdi
+	movq server_socket, %rdi
 	movq $0, %rsi
 	movq $0, %rdx
 	movq $0, %r10
 	syscall
 	cmp $-1, %rax
 	jz error
-	movq %rax, s2
+	movq %rax, connection_socket
 
 	movq $STDOUT, %rdi
 	movq $message, %rsi
@@ -116,7 +116,7 @@ loop:
 /* we're in the parent if we reach this line */
 
 	movq $__NR_close, %rax
-	movq s2, %rdi
+	movq connection_socket, %rdi
 	syscall
 	test %rax, %rax
 	jnz error
@@ -124,7 +124,7 @@ loop:
 
 exit:
 	movq $__NR_close, %rax
-	movq s, %rdi
+	movq server_socket, %rdi
 	syscall
 	test %rax, %rax
 	jnz error
@@ -148,12 +148,12 @@ error:
 
 child:
 /* we're in the child if we reach this line */
-	movq s2, %rdi
+	movq connection_socket, %rdi
-	movq s2, %rsi
+	movq connection_socket, %rsi
 	call passthru
 
 	movq $__NR_close, %rax
-	movq s2, %rdi
+	movq connection_socket, %rdi
 	syscall
 
 	movq $__NR_exit, %rax