From: David Devecsery <ddevec@gatech.edu>
Date: Tue, 19 May 2020 19:51:53 +0000 (-0400)
Subject: Updated printing functionality
X-Git-Url: https://git.devinivas.org/?a=commitdiff_plain;h=99a2f4613051dcd8594179f3af6888331043474c;p=cs3210-lab1.git

Updated printing functionality
---

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 65345c3..f40b91a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@ endif()
 project(xv6)
 
 #set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -MD -gstabs+ -Werror -fno-omit-frame-pointer -fno-stack-protector")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-strict-aliasing -Wall -gstabs -Werror -fno-omit-frame-pointer -fno-stack-protector")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-strict-aliasing -Wall -gstabs -Wno-builtin-declaration-mismatch -fno-omit-frame-pointer -fno-stack-protector")
 
 set(CMAKE_C_FLAGS_RELEASE "-O2 -DNDEBUG")
 set(CMAKE_C_FLAGS_DEBUG "-O0 -gstabs")
diff --git a/include/error.h b/include/error.h
new file mode 100644
index 0000000..7f01ffd
--- /dev/null
+++ b/include/error.h
@@ -0,0 +1,19 @@
+/* See COPYRIGHT for copyright information. */
+
+#ifndef JOS_INC_ERROR_H
+#define JOS_INC_ERROR_H
+
+enum {
+  // Kernel error codes -- keep in sync with list in lib/printfmt.c.
+  E_UNSPECIFIED   = 1,          // Unspecified or unknown problem
+  E_BAD_ENV,                    // Environment doesn't exist or otherwise
+                                // cannot be used in requested action
+  E_INVAL,                      // Invalid parameter
+  E_NO_MEM,                     // Request failed due to memory shortage
+  E_NO_FREE_ENV,                // Attempt to create a new environment beyond
+                                // the maximum allowed
+  E_FAULT,                      // Memory fault
+  MAXERROR
+};
+
+#endif  // !JOS_INC_ERROR_H */
diff --git a/include/stdarg.h b/include/stdarg.h
new file mode 100644
index 0000000..b05304d
--- /dev/null
+++ b/include/stdarg.h
@@ -0,0 +1,14 @@
+/*	$NetBSD: stdarg.h,v 1.12 1995/12/25 23:15:31 mycroft Exp $	*/
+
+#ifndef INCLUDE_STDARG_h_
+#define INCLUDE_STDARG_h_
+
+typedef __builtin_va_list va_list;
+
+#define va_start(ap, last) __builtin_va_start(ap, last)
+
+#define va_arg(ap, type) __builtin_va_arg(ap, type)
+
+#define va_end(ap) __builtin_va_end(ap)
+
+#endif  // INCLUDE_STDARG_h_
diff --git a/include/stdio.h b/include/stdio.h
new file mode 100644
index 0000000..7162092
--- /dev/null
+++ b/include/stdio.h
@@ -0,0 +1,28 @@
+#ifndef INCLUDE_STDIO_h_
+#define INCLUDE_STDIO_h_
+
+#include "stdarg.h"
+
+#ifndef NULL
+#define NULL    ((void*)0)
+#endif /* !NULL */
+
+void    cputchar(int c);
+int     getchar(void);
+int     iscons(int fd);
+
+void    printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...);
+void vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list);
+int     snprintf(char *str, int size, const char *fmt, ...);
+int vsnprintf(char *str, int size, const char *fmt, va_list);
+
+int     cprintf(const char *fmt, ...);
+int vcprintf(const char *fmt, va_list);
+
+//int     printf(const char *fmt, ...);
+int     fprintf(int fd, const char *fmt, ...);
+int vfprintf(int fd, const char *fmt, va_list);
+
+char*   readline(const char *prompt);
+
+#endif  // INCLUDE_STDIO_h_
diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 0608770..f0c4c2a 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -2,12 +2,33 @@ project(kernel ASM)
 
 include_directories(include)
 
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -static -fno-builtin -fno-pic -m32")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -static -fno-pic -m32")
 set(CMAKE_ASM_FLAGS "${CMAKE_C_FLAGS}")
 set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -m elf_i386")
 
 include(Sources.cmake)
 
+# Get libgcc...
+execute_process(COMMAND gcc -m32 -print-libgcc-file-name
+  WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+  OUTPUT_VARIABLE GCC_LIBRARY
+  OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+message(STATUS "GOT RES ${GCC_RES}")
+message(STATUS "GOT GCCVAR ${GCC_LIBRARY}")
+message(STATUS "GOT ERROR ${GCC_ERROR}")
+
+
+set (git_cmd "git")
+set (git_arg "--version")
+message(STATUS "git cmd: ${git_cmd}")
+execute_process(COMMAND ${git_cmd} ${git_arg}
+  WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+  RESULT_VARIABLE git_result
+  OUTPUT_VARIABLE git_ver)
+
+message(STATUS "git ver[${git_result}]: ${git_ver}")
+
 add_custom_command(
   OUTPUT gen/vectors.S
   COMMAND mkdir -p gen && ${CMAKE_CURRENT_SOURCE_DIR}/tools/vectors.pl > gen/vectors.S
@@ -68,7 +89,7 @@ add_custom_command(
 
 add_custom_command(
   OUTPUT kernel
-  COMMAND ld -m elf_i386 -nostdlib -T ${CMAKE_CURRENT_SOURCE_DIR}/kernel.ld -o kernel ${kernel_OBJECTS} -b binary initcode entryother
+  COMMAND ld -m elf_i386 -T ${CMAKE_CURRENT_SOURCE_DIR}/kernel.ld -o kernel ${kernel_OBJECTS} ${GCC_LIBRARY} -b binary initcode entryother
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/kernel.ld $<TARGET_OBJECTS:kernelobjs> $<TARGET_OBJECTS:vectorobj> ${CMAKE_CURRENT_BINARY_DIR}/initcode ${CMAKE_CURRENT_BINARY_DIR}/entryother) 
 
 add_custom_command(
diff --git a/kernel/Sources.cmake b/kernel/Sources.cmake
index cb6d6cc..5b5ed1a 100644
--- a/kernel/Sources.cmake
+++ b/kernel/Sources.cmake
@@ -26,6 +26,7 @@ set(kernel_SOURCES
 	src/picirq.c
 	src/pipe.c
 	src/proc.c
+  src/printfmt.c
 	src/sleeplock.c
 	src/spinlock.c
   src/stab.c
diff --git a/kernel/include/defs.h b/kernel/include/defs.h
index 85c8636..1e91224 100644
--- a/kernel/include/defs.h
+++ b/kernel/include/defs.h
@@ -18,7 +18,6 @@ void            bwrite(struct buf*);
 
 // console.c
 void            consoleinit(void);
-void            cprintf(char*, ...);
 void            consoleintr(int(*)(void));
 void            panic(char*) __attribute__((noreturn));
 
diff --git a/kernel/include/proc.h b/kernel/include/proc.h
index 59e4580..21db00a 100644
--- a/kernel/include/proc.h
+++ b/kernel/include/proc.h
@@ -4,6 +4,7 @@
 #include <stdatomic.h>
 
 #include "param.h"
+#include "mmu.h"
 
 // Per-CPU state
 struct cpu {
diff --git a/kernel/src/console.c b/kernel/src/console.c
index 2658003..d79ca55 100644
--- a/kernel/src/console.c
+++ b/kernel/src/console.c
@@ -4,6 +4,9 @@
 
 #include "asm/x86.h"
 
+#include "stdio.h"
+#include "stdarg.h"
+
 #include "types.h"
 #include "defs.h"
 #include "param.h"
@@ -13,10 +16,16 @@
 #include "fs.h"
 #include "file.h"
 #include "memlayout.h"
+#include "proc.h"
 #include "mmu.h"
 #include "proc.h"
 #include "string.h"
 
+int uartgetc(void);
+int kbdgetc(void);
+
+void cputchar(int);
+
 static void consputc(int);
 
 static int panicked = 0;
@@ -27,31 +36,36 @@ static struct {
 } cons;
 
 static void
-printint(int xx, int base, int sign)
+putch(int ch, int *cnt)
 {
-  static char digits[] = "0123456789abcdef";
-  char buf[16];
-  int i;
-  uint x;
+  cputchar(ch);
+  // This was imported from old cs3210 lab -- it doesn't do anything... so I
+  //    removed it
+  // *cnt++;
+}
 
-  if(sign && (sign = xx < 0))
-    x = -xx;
-  else
-    x = xx;
+int
+vcprintf(const char *fmt, va_list ap)
+{
+  int cnt = 0;
 
-  i = 0;
-  do{
-    buf[i++] = digits[x % base];
-  }while((x /= base) != 0);
+  vprintfmt((void*)putch, &cnt, fmt, ap);
+  return cnt;
+}
 
-  if(sign)
-    buf[i++] = '-';
+int
+cprintf(const char *fmt, ...)
+{
+  va_list ap;
+  int cnt;
 
-  while(--i >= 0)
-    consputc(buf[i]);
-}
-//PAGEBREAK: 50
+  va_start(ap, fmt);
+  cnt = vcprintf(fmt, ap);
+  va_end(ap);
 
+  return cnt;
+}
+/*
 // Print to the console. only understands %d, %x, %p, %s.
 void
 cprintf(char *fmt, ...)
@@ -81,7 +95,6 @@ cprintf(char *fmt, ...)
       printint(*argp++, 10, 1);
       break;
     case 'x':
-    case 'X':
     case 'p':
       printint(*argp++, 16, 0);
       break;
@@ -105,7 +118,7 @@ cprintf(char *fmt, ...)
   if(locking)
     release(&cons.lock);
 }
-
+*/
 void
 panic(char *s)
 {
@@ -114,8 +127,7 @@ panic(char *s)
 
   cli();
   cons.locking = 0;
-  // use lapiccpunum so that we can call panic from mycpu()
-  cprintf("lapicid %d: panic: ", lapicid());
+  cprintf("cpu with apicid %d: panic: ", lapicid());
   cprintf(s);
   cprintf("\n");
   getcallerpcs(&s, pcs);
@@ -191,6 +203,34 @@ struct {
 
 #define C(x)  ((x)-'@')  // Control-x
 
+
+// return the next input character from the console, or 0 if none waiting
+int
+cons_getc(void)
+{
+  int c;
+
+  // poll for any pending input characters,
+  // so that this function works even when interrupts are disabled
+  // (e.g., when called from the kernel monitor).
+  consoleintr(uartgetc);
+  consoleintr(kbdgetc);
+  acquire(&cons.lock);
+
+  // grab the next character from the input buffer.
+  if (input.r != input.w) {
+    c = input.buf[input.r++];
+    if (input.r == INPUT_BUF)
+      input.r = 0;
+    release(&cons.lock);
+    return c;
+  }
+  release(&cons.lock);
+  return 0;
+}
+
+
+    
 void
 consoleintr(int (*getc)(void))
 {
@@ -238,7 +278,7 @@ consoleintr(int (*getc)(void))
 int
 consoleread(struct inode *ip, char *dst, int n)
 {
-  int target;
+  uint target;
   int c;
 
   iunlock(ip);
@@ -300,3 +340,25 @@ consoleinit(void)
   ioapicenable(IRQ_KBD, 0);
 }
 
+void
+cputchar(int c)
+{
+  consputc(c);
+}
+
+int
+getchar(void)
+{
+  int c;
+
+  while ((c = cons_getc()) == 0)
+    /* do nothing */;
+  return c;
+}
+
+int
+iscons(int fdnum)
+{
+  // used by readline
+  return 1;
+}
diff --git a/kernel/src/exec.c b/kernel/src/exec.c
index 42a1d6d..bf535f9 100644
--- a/kernel/src/exec.c
+++ b/kernel/src/exec.c
@@ -1,5 +1,7 @@
 #include "asm/x86.h"
 
+#include "stdio.h"
+
 #include "types.h"
 #include "param.h"
 #include "memlayout.h"
diff --git a/kernel/src/fs.c b/kernel/src/fs.c
index 0bd4a0c..3e7a00f 100644
--- a/kernel/src/fs.c
+++ b/kernel/src/fs.c
@@ -21,6 +21,7 @@
 #include "buf.h"
 #include "file.h"
 #include "string.h"
+#include "stdio.h"
 
 #define min(a, b) ((a) < (b) ? (a) : (b))
 static void itrunc(struct inode*);
diff --git a/kernel/src/ioapic.c b/kernel/src/ioapic.c
index cb0f015..69a750a 100644
--- a/kernel/src/ioapic.c
+++ b/kernel/src/ioapic.c
@@ -5,6 +5,7 @@
 #include "types.h"
 #include "defs.h"
 #include "traps.h"
+#include "stdio.h"
 
 #define IOAPIC  0xFEC00000   // Default physical address of IO APIC
 
diff --git a/kernel/src/main.c b/kernel/src/main.c
index 30a5354..3e22d26 100644
--- a/kernel/src/main.c
+++ b/kernel/src/main.c
@@ -8,6 +8,7 @@
 #include "mmu.h"
 #include "proc.h"
 #include "string.h"
+#include "stdio.h"
 
 static void startothers(void);
 static void mpmain(void)  __attribute__((noreturn));
diff --git a/kernel/src/printfmt.c b/kernel/src/printfmt.c
new file mode 100644
index 0000000..58ccd20
--- /dev/null
+++ b/kernel/src/printfmt.c
@@ -0,0 +1,300 @@
+// Stripped-down primitive printf-style formatting routines,
+// used in common by printf, sprintf, fprintf, etc.
+// This code is also used by both the kernel and user programs.
+
+#include "types.h"
+#include "stdio.h"
+#include "string.h"
+#include "stdarg.h"
+#include "error.h"
+
+/*
+ * Space or zero padding and a field width are supported for the numeric
+ * formats only.
+ *
+ * The special format %e takes an integer error code
+ * and prints a string describing the error.
+ * The integer may be positive or negative,
+ * so that -E_NO_MEM and E_NO_MEM are equivalent.
+ */
+
+static const char * const error_string[MAXERROR] =
+{
+  [E_UNSPECIFIED] = "unspecified error",
+  [E_BAD_ENV]     = "bad environment",
+  [E_INVAL]       = "invalid parameter",
+  [E_NO_MEM]      = "out of memory",
+  [E_NO_FREE_ENV] = "out of environments",
+  [E_FAULT]       = "segmentation fault",
+};
+
+/*
+ * Print a number (base <= 16) in reverse order,
+ * using specified putch function and associated pointer putdat.
+ */
+static void
+printnum(void (*putch)(int, void*), void *putdat,
+         unsigned long long num, unsigned base, int width, int padc)
+{
+  // first recursively print all preceding (more significant) digits
+  if (num >= base)
+    printnum(putch, putdat, num / base, base, width - 1, padc);
+  else {
+    // print any needed pad characters before first digit
+    while (--width > 0)
+      putch(padc, putdat);
+  }
+
+  // then print this (the least significant) digit
+  putch("0123456789abcdef"[num % base], putdat);
+}
+
+// Get an unsigned int of various possible sizes from a varargs list,
+// depending on the lflag parameter.
+static unsigned long long
+getuint(va_list *ap, int lflag)
+{
+  if (lflag >= 2)
+    return va_arg(*ap, unsigned long long);
+  else if (lflag)
+    return va_arg(*ap, unsigned long);
+  else
+    return va_arg(*ap, unsigned int);
+}
+
+// Same as getuint but signed - can't use getuint
+// because of sign extension
+static long long
+getint(va_list *ap, int lflag)
+{
+  if (lflag >= 2)
+    return va_arg(*ap, long long);
+  else if (lflag)
+    return va_arg(*ap, long);
+  else
+    return va_arg(*ap, int);
+}
+
+
+// Main function to format and print a string.
+void printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...);
+
+void
+vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list ap)
+{
+  register const char *p;
+  register int ch, err;
+  unsigned long long num;
+  int base, lflag, width, precision, altflag;
+  char padc;
+
+  while (1) {
+    while ((ch = *(unsigned char*)fmt++) != '%') {
+      if (ch == '\0')
+        return;
+      putch(ch, putdat);
+    }
+
+    // Process a %-escape sequence
+    padc = ' ';
+    width = -1;
+    precision = -1;
+    lflag = 0;
+    altflag = 0;
+reswitch:
+    switch (ch = *(unsigned char*)fmt++) {
+
+    // flag to pad on the right
+    case '-':
+      padc = '-';
+      goto reswitch;
+
+    // flag to pad with 0's instead of spaces
+    case '0':
+      padc = '0';
+      goto reswitch;
+
+    // width field
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+      for (precision = 0;; ++fmt) {
+        precision = precision * 10 + ch - '0';
+        ch = *fmt;
+        if (ch < '0' || ch > '9')
+          break;
+      }
+      goto process_precision;
+
+    case '*':
+      precision = va_arg(ap, int);
+      goto process_precision;
+
+    case '.':
+      if (width < 0)
+        width = 0;
+      goto reswitch;
+
+    case '#':
+      altflag = 1;
+      goto reswitch;
+
+process_precision:
+      if (width < 0)
+        width = precision, precision = -1;
+      goto reswitch;
+
+    // long flag (doubled for long long)
+    case 'l':
+      lflag++;
+      goto reswitch;
+
+    // character
+    case 'c':
+      putch(va_arg(ap, int), putdat);
+      break;
+
+    // error message
+    case 'e':
+      err = va_arg(ap, int);
+      if (err < 0)
+        err = -err;
+      if (err >= MAXERROR || (p = error_string[err]) == NULL)
+        printfmt(putch, putdat, "error %d", err);
+      else
+        printfmt(putch, putdat, "%s", p);
+      break;
+
+    // string
+    case 's':
+      if ((p = va_arg(ap, char *)) == NULL)
+        p = "(null)";
+      if (width > 0 && padc != '-')
+        for (width -= strnlen(p, precision); width > 0; width--)
+          putch(padc, putdat);
+      for (; (ch = *p++) != '\0' && (precision < 0 || --precision >= 0); width--)
+        if (altflag && (ch < ' ' || ch > '~'))
+          putch('?', putdat);
+        else
+          putch(ch, putdat);
+      for (; width > 0; width--)
+        putch(' ', putdat);
+      break;
+
+    // (signed) decimal
+    case 'd':
+      num = getint(&ap, lflag);
+      if ((long long)num < 0) {
+        putch('-', putdat);
+        num = -(long long)num;
+      }
+      base = 10;
+      goto number;
+
+    // unsigned decimal
+    case 'u':
+      num = getuint(&ap, lflag);
+      base = 10;
+      goto number;
+
+    // (unsigned) octal
+    case 'o':
+      // Replace this with your code
+      putch('X', putdat);
+      putch('X', putdat);
+      putch('X', putdat);
+      break;
+
+    // pointer
+    case 'p':
+      putch('0', putdat);
+      putch('x', putdat);
+      num = (unsigned long long)
+            (uint)va_arg(ap, void *);
+      base = 16;
+      goto number;
+
+    // (unsigned) hexadecimal
+    case 'x':
+      num = getuint(&ap, lflag);
+      base = 16;
+number:
+      printnum(putch, putdat, num, base, width, padc);
+      break;
+
+    // escaped '%' character
+    case '%':
+      putch(ch, putdat);
+      break;
+
+    // unrecognized escape sequence - just print it literally
+    default:
+      putch('%', putdat);
+      for (fmt--; fmt[-1] != '%'; fmt--)
+        /* do nothing */;
+      break;
+    }
+  }
+}
+
+void
+printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...)
+{
+  va_list ap;
+
+  va_start(ap, fmt);
+  vprintfmt(putch, putdat, fmt, ap);
+  va_end(ap);
+}
+
+struct sprintbuf {
+  char *buf;
+  char *ebuf;
+  int cnt;
+};
+
+static void
+sprintputch(int ch, struct sprintbuf *b)
+{
+  b->cnt++;
+  if (b->buf < b->ebuf)
+    *b->buf++ = ch;
+}
+
+int
+vsnprintf(char *buf, int n, const char *fmt, va_list ap)
+{
+  struct sprintbuf b = { buf, buf+n-1, 0 };
+
+  if (buf == NULL || n < 1)
+    return -E_INVAL;
+
+  // print the string to the buffer
+  vprintfmt((void*)sprintputch, &b, fmt, ap);
+
+  // null terminate the buffer
+  *b.buf = '\0';
+
+  return b.cnt;
+}
+
+int
+snprintf(char *buf, int n, const char *fmt, ...)
+{
+  va_list ap;
+  int rc;
+
+  va_start(ap, fmt);
+  rc = vsnprintf(buf, n, fmt, ap);
+  va_end(ap);
+
+  return rc;
+}
+
+
diff --git a/kernel/src/proc.c b/kernel/src/proc.c
index 90f286b..c140f40 100644
--- a/kernel/src/proc.c
+++ b/kernel/src/proc.c
@@ -7,6 +7,7 @@
 #include "proc.h"
 #include "spinlock.h"
 #include "string.h"
+#include "stdio.h"
 
 struct {
   struct spinlock lock;
diff --git a/kernel/src/string.c b/kernel/src/string.c
index 3446c12..a399304 100644
--- a/kernel/src/string.c
+++ b/kernel/src/string.c
@@ -1,5 +1,5 @@
-#include "asm/x86.h"
 #include "types.h"
+#include "asm/x86.h"
 
 void*
 memset(void *dst, int c, uint n)
@@ -78,6 +78,18 @@ strncpy(char *s, const char *t, int n)
   return os;
 }
 
+ int 
+ strnlen(const char *s, uint size) 
+ { 
+   int n; 
+  
+   for (n = 0; size > 0 && *s != '\0'; s++, size--) 
+     n++; 
+   return n; 
+ } 
+ 
+
+
 // Like strncpy but guaranteed to NUL-terminate.
 char*
 safestrcpy(char *s, const char *t, int n)
@@ -103,17 +115,32 @@ strlen(const char *s)
   return n;
 }
 
-// Return a pointer to the first occurrence of 'c' in 's',
-// or a pointer to the string-ending null character if the string has no 'c'.
-char *
-strfind(const char *s, char c)
+
+int
+strcmp(const char *p, const char *q)
 {
-  for (; *s; s++)
-  {
-    if (*s == c)
-    {
-      break;
-    }
-  }
-  return (char*)s;
+  while(*p && *p == *q)
+    p++, q++;
+  return (uchar)*p - (uchar)*q;
 }
+
+char*
+strchr(const char *s, char c)
+{
+  for(; *s; s++)
+    if(*s == c)
+      return (char*)s;
+  return 0;
+}
+
+// Return a pointer to the first occurrence of 'c' in 's',
+ // or a pointer to the string-ending null character if the string has no 'c'.
+ char *
+ strfind(const char *s, char c)
+ {
+   for (; *s; s++)
+     if (*s == c)
+       break;
+   return (char*)s;
+ }
+
diff --git a/kernel/src/syscall.c b/kernel/src/syscall.c
index 59ba22f..8be3959 100644
--- a/kernel/src/syscall.c
+++ b/kernel/src/syscall.c
@@ -6,6 +6,7 @@
 #include "mmu.h"
 #include "proc.h"
 #include "syscall.h"
+#include "stdio.h"
 
 // User code makes a system call with INT T_SYSCALL.
 // System call number in %eax.
diff --git a/kernel/src/trap.c b/kernel/src/trap.c
index 327e85d..8e2d9ba 100644
--- a/kernel/src/trap.c
+++ b/kernel/src/trap.c
@@ -6,6 +6,7 @@
 #include "mmu.h"
 #include "proc.h"
 #include "traps.h"
+#include "stdio.h"
 #include "spinlock.h"
 
 // Interrupt descriptor table (shared by all CPUs).
diff --git a/kernel/src/uart.c b/kernel/src/uart.c
index 90d262d..07d5306 100644
--- a/kernel/src/uart.c
+++ b/kernel/src/uart.c
@@ -60,7 +60,7 @@ uartputc(int c)
   outb(COM1+0, c);
 }
 
-static int
+int
 uartgetc(void)
 {
   if(!uart)
diff --git a/kernel/src/vm.c b/kernel/src/vm.c
index a78e8b3..fe01481 100644
--- a/kernel/src/vm.c
+++ b/kernel/src/vm.c
@@ -7,6 +7,7 @@
 #include "proc.h"
 #include "elf.h"
 #include "string.h"
+#include "stdio.h"
 
 extern char data[];  // defined by kernel.ld
 pde_t *kpgdir;  // for use in scheduler()