[NTOS:KD] Move handling of Dmesg buffer from screen provider to KDBG provider. (#5143)

CORE-10749

The dmesg command is now available even if screen output is disabled.

Co-authored-by: Hermès Bélusca-Maïto <hermes.belusca-maito@reactos.org>

ntoskrnl/include/internal/kd.h

@@ -53,6 +53,17 @@ VOID
 
 /* INIT ROUTINES *************************************************************/
 
+KIRQL
+NTAPI
+KdbpAcquireLock(
+    _In_ PKSPIN_LOCK SpinLock);
+
+VOID
+NTAPI
+KdbpReleaseLock(
+    _In_ PKSPIN_LOCK SpinLock,
+    _In_ KIRQL OldIrql);
+
 VOID
 KdpScreenAcquire(VOID);
 

ntoskrnl/kd/kdio.c

@@ -37,14 +37,6 @@ CPPORT SerialPortInfo   = {0, DEFAULT_DEBUG_BAUD_RATE, 0};
 static CHAR KdpScreenLineBuffer[KdpScreenLineLengthDefault + 1] = "";
 static ULONG KdpScreenLineBufferPos = 0, KdpScreenLineLength = 0;
 
-const ULONG KdpDmesgBufferSize = 128 * 1024; // 512*1024;
-PCHAR KdpDmesgBuffer = NULL;
-volatile ULONG KdpDmesgCurrentPosition = 0;
-volatile ULONG KdpDmesgFreeBytes = 0;
-volatile ULONG KdbDmesgTotalWritten = 0;
-volatile BOOLEAN KdbpIsInDmesgMode = FALSE;
-static KSPIN_LOCK KdpDmesgLogSpinLock;
-
 KDP_DEBUG_MODE KdpDebugMode;
 LIST_ENTRY KdProviders = {&KdProviders, &KdProviders};
 KD_DISPATCH_TABLE DispatchTable[KdMax];
@@ -440,20 +432,12 @@ KdpScreenRelease(VOID)
     }
 }
 
-/*
- * Screen debug logger function KdpScreenPrint() writes text strings into
- * KdpDmesgBuffer, using it as a circular buffer. KdpDmesgBuffer contents could
- * be later (re)viewed using dmesg command of kdbg. KdpScreenPrint() protects
- * KdpDmesgBuffer from simultaneous writes by use of KdpDmesgLogSpinLock.
- */
 static VOID
 NTAPI
 KdpScreenPrint(PCHAR String,
                ULONG Length)
 {
     PCHAR pch = String;
-    KIRQL OldIrql;
-    ULONG beg, end, num;
 
     while (pch < String + Length && *pch)
     {
@@ -497,45 +481,6 @@ KdpScreenPrint(PCHAR String,
         HalDisplayString(KdpScreenLineBuffer + KdpScreenLineBufferPos);
         KdpScreenLineBufferPos = KdpScreenLineLength;
     }
-
-    /* Dmesg: store the string in the buffer to show it later */
-    if (KdbpIsInDmesgMode)
-       return;
-
-    if (KdpDmesgBuffer == NULL)
-        return;
-
-    /* Acquire the printing spinlock without waiting at raised IRQL */
-    OldIrql = KdbpAcquireLock(&KdpDmesgLogSpinLock);
-
-    beg = KdpDmesgCurrentPosition;
-    /* Invariant: always_true(KdpDmesgFreeBytes == KdpDmesgBufferSize); */
-    num = min(Length, KdpDmesgFreeBytes);
-    if (num != 0)
-    {
-        end = (beg + num) % KdpDmesgBufferSize;
-        if (end > beg)
-        {
-            RtlCopyMemory(KdpDmesgBuffer + beg, String, Length);
-        }
-        else
-        {
-            RtlCopyMemory(KdpDmesgBuffer + beg, String, KdpDmesgBufferSize - beg);
-            RtlCopyMemory(KdpDmesgBuffer, String + (KdpDmesgBufferSize - beg), end);
-        }
-        KdpDmesgCurrentPosition = end;
-
-        /* Counting the total bytes written */
-        KdbDmesgTotalWritten += num;
-    }
-
-    /* Release the spinlock */
-    KdbpReleaseLock(&KdpDmesgLogSpinLock, OldIrql);
-
-    /* Optional step(?): find out a way to notify about buffer exhaustion,
-     * and possibly fall into kbd to use dmesg command: user will read
-     * debug strings before they will be wiped over by next writes.
-     */
 }
 
 VOID
@@ -557,22 +502,9 @@ KdpScreenInit(
     }
     else if (BootPhase == 1)
     {
-        /* Allocate a buffer for dmesg log buffer. +1 for terminating null,
-         * see kdbp_cli.c:KdbpCmdDmesg()/2
-         */
-        KdpDmesgBuffer = ExAllocatePoolZero(NonPagedPool,
-                                            KdpDmesgBufferSize + 1,
-                                            TAG_KDBG);
-        /* Ignore failure if KdpDmesgBuffer is NULL */
-        KdpDmesgFreeBytes = KdpDmesgBufferSize;
-        KdbDmesgTotalWritten = 0;
-
         /* Take control of the display */
         KdpScreenAcquire();
 
-        /* Initialize spinlock */
-        KeInitializeSpinLock(&KdpDmesgLogSpinLock);
-
         HalDisplayString("\r\n   Screen debugging enabled\r\n\r\n");
     }
 }

ntoskrnl/kdbg/kdb_cli.c

@@ -155,14 +155,14 @@ static LONG KdbNumberOfColsTerminal = -1;
 PCHAR KdbInitFileBuffer = NULL; /* Buffer where KDBinit file is loaded into during initialization */
 BOOLEAN KdbpBugCheckRequested = FALSE;
 
-/* Vars for dmesg */
+/* Variables for Dmesg */
-/* defined in ../kd/kdio.c, declare here: */
+static const ULONG KdpDmesgBufferSize = 128 * 1024; // 512*1024;
-extern volatile BOOLEAN KdbpIsInDmesgMode;
+static PCHAR KdpDmesgBuffer = NULL;
-extern const ULONG KdpDmesgBufferSize;
+static volatile ULONG KdpDmesgCurrentPosition = 0;
-extern PCHAR KdpDmesgBuffer;
+static volatile ULONG KdpDmesgFreeBytes = 0;
-extern volatile ULONG KdpDmesgCurrentPosition;
+static volatile ULONG KdbDmesgTotalWritten = 0;
-extern volatile ULONG KdpDmesgFreeBytes;
+static volatile BOOLEAN KdbpIsInDmesgMode = FALSE;
-extern volatile ULONG KdbDmesgTotalWritten;
+static KSPIN_LOCK KdpDmesgLogSpinLock;
 
 STRING KdbPromptString = RTL_CONSTANT_STRING("kdb:> ");
 
@@ -3882,13 +3882,60 @@ KdbpCliInit(VOID)
 }
 
 
+/**
+ * @brief   Debug logger function.
+ *
+ * This function writes text strings into KdpDmesgBuffer, using it as
+ * a circular buffer. KdpDmesgBuffer contents can be later (re)viewed
+ * using the dmesg command. KdbDebugPrint() protects KdpDmesgBuffer
+ * from simultaneous writes by use of KdpDmesgLogSpinLock.
+ **/
 static VOID
 NTAPI
 KdbDebugPrint(
-    PCH Message,
+    _In_ PCHAR String,
-    ULONG Length)
+    _In_ ULONG Length)
 {
-    /* Nothing here */
+    KIRQL OldIrql;
+    ULONG beg, end, num;
+
+    /* Avoid recursive calling if we already are in Dmesg mode */
+    if (KdbpIsInDmesgMode)
+       return;
+
+    if (KdpDmesgBuffer == NULL)
+        return;
+
+    /* Acquire the printing spinlock without waiting at raised IRQL */
+    OldIrql = KdbpAcquireLock(&KdpDmesgLogSpinLock);
+
+    beg = KdpDmesgCurrentPosition;
+    /* Invariant: always_true(KdpDmesgFreeBytes == KdpDmesgBufferSize); */
+    num = min(Length, KdpDmesgFreeBytes);
+    if (num != 0)
+    {
+        end = (beg + num) % KdpDmesgBufferSize;
+        if (end > beg)
+        {
+            RtlCopyMemory(KdpDmesgBuffer + beg, String, Length);
+        }
+        else
+        {
+            RtlCopyMemory(KdpDmesgBuffer + beg, String, KdpDmesgBufferSize - beg);
+            RtlCopyMemory(KdpDmesgBuffer, String + (KdpDmesgBufferSize - beg), end);
+        }
+        KdpDmesgCurrentPosition = end;
+
+        /* Counting the total bytes written */
+        KdbDmesgTotalWritten += num;
+    }
+
+    /* Release the spinlock */
+    KdbpReleaseLock(&KdpDmesgLogSpinLock, OldIrql);
+
+    /* Optional step(?): find out a way to notify about buffer exhaustion,
+     * and possibly fall into kbd to use dmesg command: user will read
+     * debug strings before they will be wiped over by next writes. */
 }
 
 /**
@@ -3918,6 +3965,22 @@ KdbInitialize(
         /* Register as a Provider */
         InsertTailList(&KdProviders, &DispatchTable->KdProvidersList);
     }
+    else if (BootPhase == 1)
+    {
+        /* Initialize Dmesg support */
+
+        /* Allocate a buffer for Dmesg log buffer. +1 for terminating null,
+         * see kdbp_cli.c:KdbpCmdDmesg()/2 */
+        KdpDmesgBuffer = ExAllocatePoolZero(NonPagedPool,
+                                            KdpDmesgBufferSize + 1,
+                                            TAG_KDBG);
+        /* Ignore failure if KdpDmesgBuffer is NULL */
+        KdpDmesgFreeBytes = KdpDmesgBufferSize;
+        KdbDmesgTotalWritten = 0;
+
+        /* Initialize spinlock */
+        KeInitializeSpinLock(&KdpDmesgLogSpinLock);
+    }
 
     if (BootPhase <= 1)
     {