Prevent overwriting palo during kernel load

Add code to prevent overwriting palo code and data unintentionally
during load of a kernel.
Improve debug output and add the hidden command "d" to toggle debug
mode.

Signed-off-by: Helge Deller <deller@gmx.de>

2 files changed, 37 insertions, 5 deletions

diff --git a/ipl/crt0.S b/ipl/crt0.S
index d52485f..34dfc8c 100644
--- a/ipl/crt0.S
+++ b/ipl/crt0.S
@@ -13,7 +13,9 @@
 ;!
 	.section .init
 	.EXPORT $START$,entry
+	.export _start
 $START$:
+_start:
 	b,n	continue	; This branch instruction may be used
 				; by 'palo' to determine whether a boot
 				; loader file really is a boot loader, so
diff --git a/ipl/ipl.c b/ipl/ipl.c
index 19111d8..1a6d946 100644
--- a/ipl/ipl.c
+++ b/ipl/ipl.c
@@ -15,6 +15,7 @@
 #define PAGE0   ((struct zeropage *)0x00000000)
 
 char commandline[CMDLINELEN];
+extern char _end, _start, _edata;
 
 int Debug = 0;
 int interactive = 0;
@@ -161,6 +162,7 @@ int
 load_kernel(int fd, unsigned *entryp, int *wide)
 {
     struct loadable loadable;
+    void *malloc_start;
     int i;
 
     if (!prepare_loadable(fd, &loadable, wide))
@@ -176,12 +178,26 @@ load_kernel(int fd, unsigned *entryp, int *wide)
     printf("\nEntry %08x first %08x n %d\n",
 		loadable.entry, loadable.first, loadable.n);
 
+    malloc_start = malloc_aligned(0, 1);
+    malloc_start -= 5*1024*1024; /* 5 MB */
+
     for (i = 0; i < loadable.n; i++)
     {
 	loadable.segment[i].mem =  PHYS(loadable.segment[i].mem);
 	printf("Segment %d load %08x size %d mediaptr 0x%lx\n",
 		i, loadable.segment[i].mem, loadable.segment[i].length,
 		loadable.segment[i].offset);
+
+	/* check not to overwrite us */
+	if (loadable.segment[i].mem >= (unsigned long)&_end &&
+	    (loadable.segment[i].mem + loadable.segment[i].length)
+			< (unsigned long)malloc_start)
+		continue;
+
+	printf("Abort: Would overwrite palo %p-%p or data %p areas.\n",
+		&_start, &_end, malloc_start);
+	return 0;
+
     }
 
     if (!load_loadable((char *)loadable.first, fd, &loadable))
@@ -363,6 +379,9 @@ interact(int *ok)
 	    "'r'    restore command line\n"
 	    "'l'    list dir\n"
 	    "'x'    reset and reboot machine\n"
+#ifdef HIDDEN_COMMAND
+	    "'d'    toggle debug mode\n"
+#endif
 	    "? ");
 	numbuf[0] = '0';
 	numbuf[1] = '\0';
@@ -391,6 +410,16 @@ interact(int *ok)
 	if (numbuf[0] == 'x')
 	    pdc_do_reset();
 
+	if (numbuf[0] == 'd') /* hidden option! */
+	{
+	    Debug = !Debug;
+	    printf("Debug mode is now %s\n", Debug ? "on":"off");
+	    if (Debug)
+		printf("palo loaded at %p-%p.\n", &_start, &_end);
+	    continue;
+	}
+
+
 	editfield = parse_number(numbuf, &p);
 
 	if (editfield >= MAX_ARGV)
@@ -444,7 +473,6 @@ get_default_serial_console()
 unsigned
 iplmain(int is_interactive, char *initialstackptr, int started_wide)
 {
-    extern char _end, _edata;
     int partitioned;
     unsigned entry;
     struct firstblock f;
@@ -468,9 +496,12 @@ iplmain(int is_interactive, char *initialstackptr, int started_wide)
     puts(bld_info);
     puts("\n");
     interactive = is_interactive;
-    if (Debug) printf("iplmain(%d, started %s)\n", interactive,
-	started_wide ? "wide" : "narrow");
-    if (Debug) printf("initial-sp %p\n", initialstackptr);
+    if (Debug) {
+	printf("iplmain(%d, started %s)\n", interactive,
+		started_wide ? "wide" : "narrow");
+	printf("initial-sp %p\n", initialstackptr);
+	printf("palo loaded at %p-%p.\n", &_start, &_end);
+    }
 
  restart:
 
@@ -704,7 +735,6 @@ iplmain(int is_interactive, char *initialstackptr, int started_wide)
 	    }
 	}
 
-	/* FIXME!!! This *could* overwrite us -- probably should check */
 	if (!load_kernel(kernfd, &entry, &wide))
 	{
 	    die("ERROR: failed to load kernel\n");