From 3d21fff8d44ebc248060224418f4b412d6e076bd Mon Sep 17 00:00:00 2001
From: Adrien Bourmault <neox@os-k.eu>
Date: Wed, 22 May 2019 08:35:58 +0200
Subject: [PATCH] Stack Overflow and Underflow detected !

---
 kaleid/kernel/ke/idt.c    | 17 ++++-------------
 kaleid/kernel/mm/paging.c | 16 +++++++++++++++-
 kaleid/kernel/sh/shcmds.c | 12 ++++++++++++
 3 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/kaleid/kernel/ke/idt.c b/kaleid/kernel/ke/idt.c
index f877b92..b8a0c4d 100644
--- a/kaleid/kernel/ke/idt.c
+++ b/kaleid/kernel/ke/idt.c
@@ -299,12 +299,14 @@ static void EarlyExceptionHandler(ISRFrame_t *regs)
     KeHaltCPU();
 }
 
+//
+// Double Fault handling and stack overflow detection
+//
 static void DoubleFaultHandler(ISRFrame_t *regs)
 {
-    ulong StackGuardOne = (ulong)MmGetStackGuards(0);
     ulong StackGuardTwo = (ulong)MmGetStackGuards(1);
 
-    if (regs->rsp <= StackGuardTwo + 4*KB) {
+    if (regs->rsp <= StackGuardTwo + 4*KB && (regs->rsp - 4*KB <= regs->cr2)) {
         bprintf(BStdOut,
             "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Stack Overflow\n\n"
                      "  Double Fault Error code : %#x (%b)\n"
@@ -315,17 +317,6 @@ static void DoubleFaultHandler(ISRFrame_t *regs)
                      regs->ErrorCode,
                      StackGuardTwo
                  );
-    } else if (regs->rsp <= StackGuardOne) {
-        bprintf(BStdOut,
-            "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Stack Underflow\n\n"
-                     "  Double Fault Error code : %#x (%b)\n"
-                     "  Stack Guard bypassed    : %#x",
-
-                     VGA_COLOR_LIGHT_RED,
-                     regs->ErrorCode,
-                     regs->ErrorCode,
-                     StackGuardOne
-                 );
     } else {
         bprintf(BStdOut,
             "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Double Fault Abort\n\n"
diff --git a/kaleid/kernel/mm/paging.c b/kaleid/kernel/mm/paging.c
index 6f81444..b61783a 100644
--- a/kaleid/kernel/mm/paging.c
+++ b/kaleid/kernel/mm/paging.c
@@ -178,7 +178,20 @@ void *MmTranslateKPageToAddr(void *rank)
 //
 static void PagingHandler(ISRFrame_t *regs)
 {
-    bprintf(BStdOut, "\n\n%CPANIC\n[ISR 0x%x] Irrecoverable Kernel Page Fault at %p\n\n"
+    ulong StackGuardOne = (ulong)MmGetStackGuards(0);
+    if (regs->cr2 >= StackGuardOne && (regs->rsp + 4*KB >= regs->cr2)) {
+        bprintf(BStdOut,
+            "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Stack Underflow\n\n"
+                     "  Double Fault Error code : %#x (%b)\n"
+                     "  Stack Guard bypassed    : %#x",
+
+                     VGA_COLOR_LIGHT_RED,
+                     regs->ErrorCode,
+                     regs->ErrorCode,
+                     StackGuardOne
+                 );
+    } else {
+        bprintf(BStdOut, "\n\n%CPANIC\n[ISR 0x%x] Irrecoverable Kernel Page Fault at %p\n\n"
                      "  Error code : 0x%x (%b)",
 
                      VGA_COLOR_LIGHT_RED,
@@ -187,6 +200,7 @@ static void PagingHandler(ISRFrame_t *regs)
                      regs->ErrorCode,
                      regs->ErrorCode
                  );
+    }
 
     KeBrkDumpRegisters(regs);
 
diff --git a/kaleid/kernel/sh/shcmds.c b/kaleid/kernel/sh/shcmds.c
index 41d6eb4..dffa874 100644
--- a/kaleid/kernel/sh/shcmds.c
+++ b/kaleid/kernel/sh/shcmds.c
@@ -203,6 +203,17 @@ error_t CmdStackOverflow(int argc, char **argv, char *cmdline)
     return EOK;
 }
 
+error_t CmdStackUnderflow(int argc, char **argv, char *cmdline)
+{
+    KernLog("\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n"
+            "\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n"
+            "\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n"
+            "\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n"
+            "\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n%p\n"
+            );
+    return EOK;
+}
+
 error_t CmdMemUsage(int argc, char **argv, char *cmdline);
 
 error_t CmdVersion(int argc, char **argv, char *cmdline)
@@ -238,6 +249,7 @@ Command_t cmdtable[] =
     { "quit",       CmdQuit,            "Alias for 'exit'" },
     { "shell",      CmdShell,           "Start a new shell (nested)", },
     { "stkov",      CmdStackOverflow,   "Provoke a stack overflow" },
+    { "stkun",      CmdStackUnderflow,   "Provoke a stack underflow" },
     { "time",       CmdTime,            "Print time" },
     { "ver",        CmdVersion,         "Version and legal infos" },
     { NULL, NULL, NULL }