From e2be315cfc87395a7301d7eefe88caee2609c06d Mon Sep 17 00:00:00 2001
From: Ali Mashtizadeh <mashti@uwaterloo.ca>
Date: Sun, 1 Oct 2023 19:47:26 -0400
Subject: [PATCH] Reentrant strtok for kernel debugger

---
 include/string.h  |  1 +
 lib/libc/string.c | 15 +++++++++++----
 sys/kern/debug.c  | 13 +++++--------
 sys/kern/libc.c   | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/include/string.h b/include/string.h
index ce6025f..e228e61 100644
--- a/include/string.h
+++ b/include/string.h
@@ -19,6 +19,7 @@ char *strcat(char *s, const char *append);
 char *strncat(char *s, const char *append, size_t count);
 
 char *strtok(char *str, const char *delim);
+char *strtok_r(char *str, const char *delim, char **last);
 
 #endif /* __STRING_H__ */
 
diff --git a/lib/libc/string.c b/lib/libc/string.c
index a0e9aaf..8915dd0 100644
--- a/lib/libc/string.c
+++ b/lib/libc/string.c
@@ -119,13 +119,12 @@ strlen(const char *str)
 }
 
 char *
-strtok(char *str, const char *delim)
+strtok_r(char *str, const char *delim, char **last)
 {
     char *rval;
-    static char *last;
 
     if (str == NULL)
-	str = last;
+	str = *last;
 
     // Skip deliminaters in the front
     while ((str[0] != '\0') && strchr(delim, str[0])) {
@@ -148,11 +147,19 @@ strtok(char *str, const char *delim)
 	str[0] = '\0';
 	str++;
     }
-    last = str;
+    *last = str;
 
     return rval;
 }
 
+char *
+strtok(char *str, const char *delim)
+{
+    static char *last;
+
+    return strtok_r(str, delim, &last);
+}
+
 void *
 memset(void *dst, int c, size_t length)
 {
diff --git a/sys/kern/debug.c b/sys/kern/debug.c
index f61d621..95aa9e3 100644
--- a/sys/kern/debug.c
+++ b/sys/kern/debug.c
@@ -249,7 +249,7 @@ Debug_Prompt()
 {
     int argc;
     char *argv[DEBUG_MAX_ARGS];
-    char *nextArg;
+    char *nextArg, *last;
     char buf[DEBUG_MAX_LINE];
 
     kprintf("Entered Debugger!\n");
@@ -266,16 +266,13 @@ Debug_Prompt()
 	Console_Gets((char *)&buf, DEBUG_MAX_LINE);
 
 	// parse input
-	argv[0] = buf;
-	for (argc = 1; argc < DEBUG_MAX_ARGS; argc++) {
-	    nextArg = strchr(argv[argc - 1], ' ');
+	nextArg = strtok_r(buf, " \t\r\n", &last);
+	for (argc = 0; argc < DEBUG_MAX_ARGS; argc++) {
 	    if (nextArg == NULL)
-	    {
 		break;
-	    }
 
-	    *nextArg = '\0';
-	    argv[argc] = nextArg + 1;
+	    argv[argc] = nextArg;
+	    nextArg = strtok_r(NULL, " \t\r\n", &last);
 	}
 
 	if (strcmp(argv[0], "continue") == 0) {
diff --git a/sys/kern/libc.c b/sys/kern/libc.c
index 22bc6a3..51c28ec 100644
--- a/sys/kern/libc.c
+++ b/sys/kern/libc.c
@@ -20,6 +20,40 @@ strchr(const char *s, int c)
     }
 }
 
+char *
+strtok_r(char *str, const char *delim, char **last)
+{
+    char *rval;
+
+    if (str == NULL)
+	str = *last;
+
+    // Skip deliminaters in the front
+    while ((str[0] != '\0') && strchr(delim, str[0])) {
+	str++;
+    }
+
+    // We've reached the end of the string
+    if (str[0] == '\0')
+	return NULL;
+
+    // Return first non-delim until the next
+    rval = str;
+
+    // Skip deliminaters in the front
+    while ((str[0] != '\0') && !strchr(delim, str[0])) {
+	str++;
+    }
+
+    if (str[0] != '\0') {
+	str[0] = '\0';
+	str++;
+    }
+    *last = str;
+
+    return rval;
+}
+
 char *
 strcpy(char *to, const char *from)
 {