From c1ec955152b48b7938d20e9cba8b6e67479c2e73 Mon Sep 17 00:00:00 2001
From: Javier <dev.git@javispedro.com>
Date: Sun, 1 Nov 2026 02:07:26 +0100
Subject: add a signature mechanism for ioctl control strings

---
 dos/chud.c | 52 ++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 10 deletions(-)

(limited to 'dos/chud.c')

diff --git a/dos/chud.c b/dos/chud.c
index c6d728c..498d97b 100644
--- a/dos/chud.c
+++ b/dos/chud.c
@@ -20,11 +20,13 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
+#include <errno.h>
 #include <dos.h>
 #include <dosfunc.h>
 #include <io.h>
 
 #include "inc/mbr.h"
+#include "inc/dosapi.h"
 #include "inc/dosdrv.h"
 
 #include "chudisk.h"
@@ -56,11 +58,10 @@ static int ioctl_read_control(uint8_t drive, void *buffer, int len)
 	regs.x.dx = FP_OFF(buffer);
 
 	intdos(&regs, &regs);
-
 	if (regs.x.cflag) {
-		return -1;
+		return -1; // Generic error, but errno should be properly set
 	} else {
-		return regs.x.ax;
+		return regs.x.ax; // Number of bytes read
 	}
 }
 
@@ -74,7 +75,6 @@ static int ioctl_write_control(uint8_t drive, void *buffer, int len)
 	regs.x.dx = FP_OFF(buffer);
 
 	intdos(&regs, &regs);
-
 	if (regs.x.cflag) {
 		return -1;
 	} else {
@@ -98,9 +98,34 @@ static int ioctl_read_abs_sector(uint8_t drive, void *buffer, uint32_t sector, i
 	regs.h.cl = CHUDISK_IOCTL_DISK_READ_ABS_SECTOR;
 	regs.x.dx = FP_OFF(&ciod);
 
-	intdos(&regs, &regs);
-
-	return regs.x.cflag ? -1 : 0;
+	if (intdos(&regs, &regs) == 0) {
+		return 0;
+	} else {
+		struct DOSERROR err;
+		// Get the extended error from DOS, more useful than a simple EACCES
+		// and translate to watcom's errno
+		switch (dosexterr(&err)) {
+		case DOS_ERROR_INVALID_FUNCTION:
+			errno = EINVAL;
+			break;
+		case DOS_ERROR_FILE_NOT_FOUND:
+		case DOS_ERROR_PATH_NOT_FOUND:
+			errno = ENOENT;
+			break;
+		case DOS_ERROR_INVALID_DRIVE:
+			errno = ENODEV;
+			break;
+		case DOS_ERROR_READ_FAULT:
+		case DOS_ERROR_WRITE_FAULT:
+		case DOS_ERROR_GEN_FAILURE:
+			errno = EIO;
+			break;
+		default:
+			errno = EFAULT;
+			break;
+		}
+		return -errno;
+	}
 }
 
 static void dos_disk_reset()
@@ -123,6 +148,11 @@ static int parse_chudisk_control_string(const char *b, int len)
 	}
 	i = 0;
 #endif
+	// signature
+	if (b[i] != 'C' || b[i+1] != 'H') {
+		return -1;
+	}
+	i+=2;
 	while (i < len) {
 		char c = b[i++];
 		switch (c) {
@@ -345,7 +375,7 @@ static void usage()
 
 int main(int argc, const char *argv[])
 {
-	static char buffer[16];
+	static char buffer[32];
 	int i;
 	unsigned part;
 
@@ -399,10 +429,12 @@ int main(int argc, const char *argv[])
 	dos_disk_reset(); // Flush caches before we swap the drive...
 
 	i = 0;
-	buffer[i++] = 'S';
+	buffer[i++] = 'C'; // Signature
+	buffer[i++] = 'H';
+	buffer[i++] = 'S'; // Partition start sector
 	memcpy(&buffer[i], &partinfo[part-1].start_sector, sizeof(uint32_t));
 	i+=sizeof(uint32_t);
-	buffer[i++] = 'L';
+	buffer[i++] = 'L'; // Partition len
 	memcpy(&buffer[i], &partinfo[part-1].num_sectors, sizeof(uint32_t));
 	i+=sizeof(uint32_t);
 	buffer[i] = '\0';
-- 
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