From 14fa1df99dd6a916d1567e711555a998cdff3222 Mon Sep 17 00:00:00 2001
From: Thomas Oltmann <thomas.oltmann.hhg@gmail.com>
Date: Sat, 15 Mar 2025 15:05:51 +0100
Subject: [PATCH] Implemented a troubleshooting REPL to find out whats wrong
 with VMX

---
 src/efi.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 122 insertions(+), 1 deletion(-)

diff --git a/src/efi.c b/src/efi.c
index b14c057..5a968d3 100644
--- a/src/efi.c
+++ b/src/efi.c
@@ -7,6 +7,9 @@
 #include "bootstrap.h"
 #include "procvisor.h"
 
+#include "x86/msr.h"
+#include "x86/vmx.h"
+
 struct virt_vtable *virt = &virt_vtable_intel;
 
 static char virt_err[100];
@@ -20,6 +23,123 @@ bs_alloc(size_t size)
 	return ptr;
 }
 
+/* Troubleshooting REPL */
+static void
+checked_vmwrite(uint64_t field, uint64_t value)
+{
+	uint64_t status = vmwrite(field, value);
+	if (status & (1 << 0)) {
+		AsciiPrint("vmwrite(%lx): Invalid VMCS Pointer\n", field);
+	}
+	if (status & (1 << 6)) {
+		AsciiPrint("vmwrite(%lx): %a\n", vmcs_describe_error());
+	}
+}
+
+static CHAR16 ts_cmd[200];
+
+static void
+ts_skipws(CHAR16 **ptr)
+{
+	CHAR16 *cur = *ptr;
+	while (*cur == ' ' || *cur == '\t') cur++;
+	*ptr = cur;
+}
+
+static inline int
+hexvalue(int chr)
+{
+	if (chr >= '0' && chr <= '9') return chr - '0';
+	if (chr >= 'A' && chr <= 'Z') return chr - 'A' + 10;
+	if (chr >= 'a' && chr <= 'z') return chr - 'a' + 10;
+	return -1;
+}
+
+static bool
+ts_parsehex(CHAR16 **ptr, uint64_t *value)
+{
+	*value = 0;
+
+	CHAR16 *cur = *ptr;
+	if (hexvalue(*cur) < 0) {
+		return false;
+	}
+
+	int ndigits = 0;
+	while (hexvalue(*cur) >= 0) {
+		if (ndigits >= 16) {
+			return false;
+		}
+		*value <<= 4;
+		*value |= hexvalue(*cur);
+		ndigits++;
+		cur++;
+	}
+
+	*ptr = cur;
+	return true;
+}
+
+static void
+ts_repl(void)
+{
+	for (;;) {
+		Input(L"> ", ts_cmd, sizeof ts_cmd);
+		Print(L"\n");
+
+		uint64_t index, value, status;
+
+		CHAR16 *cur = ts_cmd;
+		ts_skipws(&cur);
+		switch (*cur++) {
+
+		case 0:
+			break;
+
+		case 'm':
+			ts_skipws(&cur);
+			if (!ts_parsehex(&cur, &index)) goto huh;
+			if (*cur) {
+				if (!ts_parsehex(&cur, &value)) goto huh;
+				writemsr64(index, value);
+			} else {
+				value = readmsr64(index);
+			}
+			if (*cur) goto huh;
+			AsciiPrint("MSR %lx = %lx\n", index, value);
+			break;
+
+		case 'v':
+			ts_skipws(&cur);
+			if (!ts_parsehex(&cur, &index)) goto huh;
+			if (*cur) {
+				if (!ts_parsehex(&cur, &value)) goto huh;
+				checked_vmwrite(index, value);
+			} else {
+				value = vmread(index);
+			}
+			if (*cur) goto huh;
+			AsciiPrint("VMCS FIELD %lx = %lx\n", index, value);
+			break;
+
+		case 'l':
+			AsciiPrint("VMLAUNCH\n");
+			status = vmlaunch();
+			if (status & (1 << 0)) {
+				Print(L"Invalid VMCS Pointer\n");
+			}
+			if (status & (1 << 6)) {
+				AsciiPrint("%a\n", vmcs_describe_error());
+			}
+			break;
+
+huh:		default:
+			AsciiPrint("?\n");
+			break;
+		}
+	}
+}
+
 EFIAPI
 EFI_STATUS
 efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE *systemTable)
@@ -43,7 +163,8 @@ efi_main(EFI_HANDLE imageHandle, EFI_SYSTEM_TABLE *systemTable)
 		AsciiPrint("* VT-x enabled!\n");
 	}
 
-	for (;;) {}
+	//for (;;) {}
+	ts_repl();
 
 	return EFI_SUCCESS;
 }