X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/1a602f0313ae7b0b5e49bae434616373bb7ca681..d0912d1f5b4c65b0be0c3fba2a264a1cfbf96d08:/winmisc.c

diff --git a/winmisc.c b/winmisc.c
index 22663419..2590befe 100644
--- a/winmisc.c
+++ b/winmisc.c
@@ -35,3 +35,251 @@ int filename_is_null(Filename fn)
 {
     return !*fn.path;
 }
+
+#ifdef DEBUG
+static FILE *debug_fp = NULL;
+static HANDLE debug_hdl = INVALID_HANDLE_VALUE;
+static int debug_got_console = 0;
+
+void dputs(char *buf)
+{
+    DWORD dw;
+
+    if (!debug_got_console) {
+	if (AllocConsole()) {
+	    debug_got_console = 1;
+	    debug_hdl = GetStdHandle(STD_OUTPUT_HANDLE);
+	}
+    }
+    if (!debug_fp) {
+	debug_fp = fopen("debug.log", "w");
+    }
+
+    if (debug_hdl != INVALID_HANDLE_VALUE) {
+	WriteFile(debug_hdl, buf, strlen(buf), &dw, NULL);
+    }
+    fputs(buf, debug_fp);
+    fflush(debug_fp);
+}
+#endif
+
+#ifdef MINEFIELD
+/*
+ * Minefield - a Windows equivalent for Electric Fence
+ */
+
+#define PAGESIZE 4096
+
+/*
+ * Design:
+ * 
+ * We start by reserving as much virtual address space as Windows
+ * will sensibly (or not sensibly) let us have. We flag it all as
+ * invalid memory.
+ * 
+ * Any allocation attempt is satisfied by committing one or more
+ * pages, with an uncommitted page on either side. The returned
+ * memory region is jammed up against the _end_ of the pages.
+ * 
+ * Freeing anything causes instantaneous decommitment of the pages
+ * involved, so stale pointers are caught as soon as possible.
+ */
+
+static int minefield_initialised = 0;
+static void *minefield_region = NULL;
+static long minefield_size = 0;
+static long minefield_npages = 0;
+static long minefield_curpos = 0;
+static unsigned short *minefield_admin = NULL;
+static void *minefield_pages = NULL;
+
+static void minefield_admin_hide(int hide)
+{
+    int access = hide ? PAGE_NOACCESS : PAGE_READWRITE;
+    VirtualProtect(minefield_admin, minefield_npages * 2, access, NULL);
+}
+
+static void minefield_init(void)
+{
+    int size;
+    int admin_size;
+    int i;
+
+    for (size = 0x40000000; size > 0; size = ((size >> 3) * 7) & ~0xFFF) {
+	minefield_region = VirtualAlloc(NULL, size,
+					MEM_RESERVE, PAGE_NOACCESS);
+	if (minefield_region)
+	    break;
+    }
+    minefield_size = size;
+
+    /*
+     * Firstly, allocate a section of that to be the admin block.
+     * We'll need a two-byte field for each page.
+     */
+    minefield_admin = minefield_region;
+    minefield_npages = minefield_size / PAGESIZE;
+    admin_size = (minefield_npages * 2 + PAGESIZE - 1) & ~(PAGESIZE - 1);
+    minefield_npages = (minefield_size - admin_size) / PAGESIZE;
+    minefield_pages = (char *) minefield_region + admin_size;
+
+    /*
+     * Commit the admin region.
+     */
+    VirtualAlloc(minefield_admin, minefield_npages * 2,
+		 MEM_COMMIT, PAGE_READWRITE);
+
+    /*
+     * Mark all pages as unused (0xFFFF).
+     */
+    for (i = 0; i < minefield_npages; i++)
+	minefield_admin[i] = 0xFFFF;
+
+    /*
+     * Hide the admin region.
+     */
+    minefield_admin_hide(1);
+
+    minefield_initialised = 1;
+}
+
+static void minefield_bomb(void)
+{
+    div(1, *(int *) minefield_pages);
+}
+
+static void *minefield_alloc(int size)
+{
+    int npages;
+    int pos, lim, region_end, region_start;
+    int start;
+    int i;
+
+    npages = (size + PAGESIZE - 1) / PAGESIZE;
+
+    minefield_admin_hide(0);
+
+    /*
+     * Search from current position until we find a contiguous
+     * bunch of npages+2 unused pages.
+     */
+    pos = minefield_curpos;
+    lim = minefield_npages;
+    while (1) {
+	/* Skip over used pages. */
+	while (pos < lim && minefield_admin[pos] != 0xFFFF)
+	    pos++;
+	/* Count unused pages. */
+	start = pos;
+	while (pos < lim && pos - start < npages + 2 &&
+	       minefield_admin[pos] == 0xFFFF)
+	    pos++;
+	if (pos - start == npages + 2)
+	    break;
+	/* If we've reached the limit, reset the limit or stop. */
+	if (pos >= lim) {
+	    if (lim == minefield_npages) {
+		/* go round and start again at zero */
+		lim = minefield_curpos;
+		pos = 0;
+	    } else {
+		minefield_admin_hide(1);
+		return NULL;
+	    }
+	}
+    }
+
+    minefield_curpos = pos - 1;
+
+    /*
+     * We have npages+2 unused pages starting at start. We leave
+     * the first and last of these alone and use the rest.
+     */
+    region_end = (start + npages + 1) * PAGESIZE;
+    region_start = region_end - size;
+    /* FIXME: could align here if we wanted */
+
+    /*
+     * Update the admin region.
+     */
+    for (i = start + 2; i < start + npages + 1; i++)
+	minefield_admin[i] = 0xFFFE;   /* used but no region starts here */
+    minefield_admin[start + 1] = region_start % PAGESIZE;
+
+    minefield_admin_hide(1);
+
+    VirtualAlloc((char *) minefield_pages + region_start, size,
+		 MEM_COMMIT, PAGE_READWRITE);
+    return (char *) minefield_pages + region_start;
+}
+
+static void minefield_free(void *ptr)
+{
+    int region_start, i, j;
+
+    minefield_admin_hide(0);
+
+    region_start = (char *) ptr - (char *) minefield_pages;
+    i = region_start / PAGESIZE;
+    if (i < 0 || i >= minefield_npages ||
+	minefield_admin[i] != region_start % PAGESIZE)
+	minefield_bomb();
+    for (j = i; j < minefield_npages && minefield_admin[j] != 0xFFFF; j++) {
+	minefield_admin[j] = 0xFFFF;
+    }
+
+    VirtualFree(ptr, j * PAGESIZE - region_start, MEM_DECOMMIT);
+
+    minefield_admin_hide(1);
+}
+
+static int minefield_get_size(void *ptr)
+{
+    int region_start, i, j;
+
+    minefield_admin_hide(0);
+
+    region_start = (char *) ptr - (char *) minefield_pages;
+    i = region_start / PAGESIZE;
+    if (i < 0 || i >= minefield_npages ||
+	minefield_admin[i] != region_start % PAGESIZE)
+	minefield_bomb();
+    for (j = i; j < minefield_npages && minefield_admin[j] != 0xFFFF; j++);
+
+    minefield_admin_hide(1);
+
+    return j * PAGESIZE - region_start;
+}
+
+void *minefield_c_malloc(size_t size)
+{
+    if (!minefield_initialised)
+	minefield_init();
+    return minefield_alloc(size);
+}
+
+void minefield_c_free(void *p)
+{
+    if (!minefield_initialised)
+	minefield_init();
+    minefield_free(p);
+}
+
+/*
+ * realloc _always_ moves the chunk, for rapid detection of code
+ * that assumes it won't.
+ */
+void *minefield_c_realloc(void *p, size_t size)
+{
+    size_t oldsize;
+    void *q;
+    if (!minefield_initialised)
+	minefield_init();
+    q = minefield_alloc(size);
+    oldsize = minefield_get_size(p);
+    memcpy(q, p, (oldsize < size ? oldsize : size));
+    minefield_free(p);
+    return q;
+}
+
+#endif				/* MINEFIELD */