Feature/usys transition

.gitignore

@@ -11,7 +11,8 @@ entryother
 initcode
 initcode.out
 kernelmemfs
-mkfs
+tools/mkfs
+tools/usys
 kernel/kernel
 user/usys.S
 .gdbinit

ADDING_SYSCALLS.md

@@ -0,0 +1,34 @@
+# Adding Syscalls to XV6
+
+The tools/usys.c programm uses the syscall.h to create the user/usys.S (See Makefile).
+The following steps are necessary to add a syscall to xv6. 
+
+## Checklist
+
+- update kernel/syscall.h to contain the new syscall name. Example:
+  - #define SYS_freepg 22
+- update kernel/syscall.c. Example:
+  - extern uint64 sys_freepg(void);
+  - [SYS_freepg]  sys_freepg,
+- update kernel/defs.h. Example:
+  - Below //kalloc.c  -> See assumes the the function freepg() is defined in kalloc.c
+  - int             freepg(void);
+- update kernel/sysproc.c. Example:
+  - uint64
+  - sys_freepg(void) { return freepg()};
+- update user/user.h. Example:
+  - Below // system calls
+  - int freepg(void);
+
+Remark: Before the change to usys.c you had to addionaly update user/usys.pl to reflect the changes. 
+
+## Ideas
+
+- It would be good if I could reduce the places which are required to add a new system call. Ideally only 1-2 Files (kernel and user) should be updated. Best would be only one file.
+
+
+
+
+
+
+

Makefile

@@ -1,5 +1,7 @@
 K=kernel
 U=user
+T=tools
+
 
 OBJS = \
   $K/entry.o \
@@ -101,8 +103,13 @@ _%: %.o $(ULIB)
 	$(OBJDUMP) -S $@ > $*.asm
 	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
 
-$U/usys.S : $U/usys.pl
-	perl $U/usys.pl > $U/usys.S
+# Compile usys generator, this replaces the usys.pl script
+$T/usys: $T/usys.c
+	gcc -Werror -Wall -I. -o $T/usys $T/usys.c
+
+# Generate usys.S
+$U/usys.S: $T/usys
+	$T/usys $U/usys.S
 
 $U/usys.o : $U/usys.S
 	$(CC) $(CFLAGS) -c -o $U/usys.o $U/usys.S
@@ -113,8 +120,8 @@ $U/_forktest: $U/forktest.o $(ULIB)
 	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $U/_forktest $U/forktest.o $U/ulib.o $U/usys.o
 	$(OBJDUMP) -S $U/_forktest > $U/forktest.asm
 
-mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
-	gcc -Werror -Wall -I. -o mkfs/mkfs mkfs/mkfs.c
+$T/mkfs: $T/mkfs.c $K/fs.h $K/param.h
+	gcc -Werror -Wall -I. -o $T/mkfs $T/mkfs.c
 
 # Prevent deletion of intermediate files, e.g. cat.o, after first build, so
 # that disk image changes after first build are persistent until clean.  More
@@ -140,17 +147,17 @@ UPROGS=\
 	$U/_wc\
 	$U/_zombie\
 
-fs.img: mkfs/mkfs README $(UPROGS)
-	mkfs/mkfs fs.img README $(UPROGS)
+fs.img: $T/mkfs README $(UPROGS)
+	$T/mkfs fs.img README $(UPROGS)
 
 -include kernel/*.d user/*.d
 
 clean: 
 	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
 	*/*.o */*.d */*.asm */*.sym \
 	$U/initcode $U/initcode.out $K/kernel fs.img \
-	mkfs/mkfs .gdbinit \
-        $U/usys.S \
+	$T/mkfs .gdbinit \
+    $T/usys $U/usys.S \
 	$(UPROGS)
 
 # try to generate a unique GDB port

tools/usys.c

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define MAX_LINE_LENGTH 256
+
+int main(int argc, char *argv[]) {
+    if (argc < 2) {
+        fprintf(stderr, "Usage: %s <output_file>\n", argv[0]);
+        return 1;
+    }
+
+    // Open syscall.h for reading
+    FILE *syscall_h = fopen("kernel/syscall.h", "r");
+    if (!syscall_h) {
+        fprintf(stderr, "Error opening syscall.h file\n");
+        return 1;
+    }
+
+    // Open the user-provided output file
+    FILE *output = fopen(argv[1], "w");
+    if (!output) {
+        fprintf(stderr, "Error creating %s file\n", argv[1]);
+        fclose(syscall_h);
+        return 1;
+    }
+
+    // Header in the output file
+    fprintf(output, "# generated by usys.c - do not edit\n#include \"kernel/syscall.h\"\n");
+
+    char line[MAX_LINE_LENGTH];
+    while (fgets(line, sizeof(line), syscall_h)) {
+        // Look for lines starting with "#define SYS_"
+        if (strncmp(line, "#define SYS_", 12) == 0) {
+            char syscall_name[50];
+
+            // Extract the system call name and number
+            if (sscanf(line, "#define SYS_%s", syscall_name) == 1) {
+                // Write the assembly stub for this system call, using the syscall name
+                fprintf(output, ".global %s\n", syscall_name);
+                fprintf(output, "%s:\n", syscall_name);
+                fprintf(output, " li a7, SYS_%s\n", syscall_name);  
+                fprintf(output, " ecall\n");                    // Make the syscall
+                fprintf(output, " ret\n");                    // Return
+            }
+        }
+    }
+
+    fclose(syscall_h);
+    fclose(output);
+
+    printf("Assembly stubs successfully generated in %s.\n", argv[1]);
+
+    return 0;
+}