Add getpid syscall and test it

Author: hialvaro

sys_call_table.S

@@ -2,17 +2,27 @@
 #include <segment.h>
 
 ENTRY (sys_call_table)
-	.long sys_ni_syscall//0
-	.long sys_ni_syscall//1
-	.long sys_ni_syscall//2
-	.long sys_ni_syscall//3
-	.long sys_write//4
-	.long sys_ni_syscall//5
-	.long sys_ni_syscall//6
-	.long sys_ni_syscall//7
-	.long sys_ni_syscall//8
-	.long sys_ni_syscall//9
-	.long sys_gettime//10
+	.long sys_ni_syscall //0
+	.long sys_ni_syscall //1
+	.long sys_ni_syscall //2
+	.long sys_ni_syscall //3
+	.long sys_write //4
+	.long sys_ni_syscall //5
+	.long sys_ni_syscall //6
+	.long sys_ni_syscall //7
+	.long sys_ni_syscall //8
+	.long sys_ni_syscall //9
+	.long sys_gettime //10
+	.long sys_ni_syscall //11
+	.long sys_ni_syscall //12
+	.long sys_ni_syscall //13
+	.long sys_ni_syscall //14
+	.long sys_ni_syscall //15
+	.long sys_ni_syscall //16
+	.long sys_ni_syscall //17
+	.long sys_ni_syscall //18
+	.long sys_ni_syscall //19
+	.long sys_getpid //20
 
 .globl MAX_SYSCALL
 MAX_SYSCALL = (. - sys_call_table)/4

user.c

@@ -20,19 +20,28 @@ int __attribute__ ((__section__(".text.main")))
 
   /********WRITE********/
   if(write(1, "------- \n", 9) == -1) perror();
-  if(write(1, "\nWrite from user.c\n", 19) == -1) perror();
+  char * mesg;
+  mesg = "\n [write] Write from user.c\n";
+  if(write(1, mesg, strlen(mesg)) == -1) perror();
   if(write(1, "------- \n", 9) == -1) perror();
 
 
   /*****GETTIME********/
-  char * time_text;
-  time_text = "\nTesting gettime() from user.c: ";
-  if(write(1, time_text, strlen(time_text)) == -1) perror();
-  itoa(gettime(), time_text); 
-  if(write(1, time_text, strlen(time_text)) == -1) perror();
-  if(write(1, " (gettime result)\n", 18) == -1) perror();
+  mesg = "\n [gettime] Testing gettime() from user.c: ";
+  if(write(1, mesg, strlen(mesg)) == -1) perror();
+  itoa(gettime(), mesg); 
+  if(write(1, mesg, strlen(mesg)) == -1) perror();
+  mesg = " (gettime result)\n";
+  if(write(1, mesg, strlen(mesg)) == -1) perror();
   if(write(1, "------- \n", 9) == -1) perror();
 
+/**********GETPID********/
+mesg = "\n [getpid] My PID: ";
+if(write(1, mesg, strlen(mesg)) == -1) perror();
+int pid = getpid();
+itoa(pid, mesg);
+if(write(1, mesg, strlen(mesg)) == -1) perror();
+if(write(1, "\n ------- \n", 9) == -1) perror();
 
   while(1) { 
   	//int val1 = add(0x42, 0x666);

wrappers.S

@@ -81,5 +81,46 @@ gt_return:
 	mov %eax, errno
 	mov -1, %eax
 gt_no_error:
+	pop %ebp
+	ret
+
+
+ENTRY(getpid)
+	push %ebp
+	mov %esp,%ebp
+	
+	# Save to user stack
+	push %edx
+	push %ecx
+	
+
+	# Now we need to put the identified of the system call in the EAX register
+	movl $20, %eax
+	
+	# EDX and ECX will be modified by sysexit. We must save them so we can restore them.
+	#push %ecx
+	#push %edx
+
+	# Fake dynamic link?
+	push $gp_return
+	push %ebp
+	mov %esp,%ebp
+
+	# Entramos
+	sysenter
+
+gp_return:
+	# Comprobamos si hay error en la ejecución de la syscall
+	pop %ebp
+	add $4, %esp
+	pop %edx
+	pop %ecx
+	cmp $0, %eax
+	jge gp_no_error
+	# Si hay error, preparamos el contexto para retornar correctamente el código.
+	neg %eax # Negamos EAX para obtener el valor absoluto
+	mov %eax, errno
+	mov -1, %eax
+gp_no_error:
 	pop %ebp
 	ret