*** empty log message ***

lib/mmap-stack.c

@@ -0,0 +1,86 @@
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdarg.h>
+#if HAVE_SYS_MMAN_H
+# include <sys/mman.h>
+#endif
+#if HAVE_UCONTEXT_H
+# include <ucontext.h>
+#endif
+
+#include "mmap-stack.h"
+
+#ifndef MAP_ANONYMOUS
+# define MAP_ANONYMOUS 0
+#endif
+
+/* Set up context, *CTX, so that it may be used via makecontext,
+   using a block of SIZE bytes of mmap'd memory for its stack.
+   Return nonzero upon error.  */
+static int
+get_context (ucontext_t *ctx, size_t size)
+{
+  void *stack;
+  int fd = 0;
+
+  if (getcontext (ctx))
+    return 1;
+
+  /* use tmpfile if MAP_ANONYMOUS is not defined. */
+#if MAP_ANONYMOUS == 0
+  {
+    FILE *fp = tmpfile ();
+    if (!fp)
+      return 1;
+    fd = fileno (fp);
+  }
+#endif
+
+  stack = mmap (NULL, size,
+		PROT_READ | PROT_WRITE,
+		MAP_PRIVATE | MAP_ANONYMOUS, fd, 0);
+  if (stack == MAP_FAILED)
+    return 1;
+  ctx->uc_stack.ss_sp = stack;
+  ctx->uc_stack.ss_size = size;
+  ctx->uc_link = NULL;
+  return 0;
+}
+
+/* Yep, this is arbitrary.  tough :-)  */
+#define ARGC_MAX 6
+
+/* Set up a context without conventional stack limitations,
+   then call function FUNC with the specified number (ARGC) of arguments.
+   If get_context and setcontext succeed, this function does not return,
+   so FUNC must be sure to exit appropriately.  Otherwise, this function
+   does return, and the caller should diagnose the failure.  */
+void
+run_on_mmaped_stack (void (*func) (void), size_t argc, ...)
+{
+    ucontext_t ctx;
+    size_t size = 1024 * 1024 * 1024;
+    long bs_argv[ARGC_MAX];
+    unsigned i;
+    va_list ap;
+
+    va_start (ap, argc);
+    for (i = 0; i < argc; i++)
+      bs_argv[i] = va_arg (ap, long);
+    va_end (ap);
+
+    if (get_context (&ctx, size) == 0)
+      {
+	makecontext (&ctx, func, argc,
+		     bs_argv[0], bs_argv[1], bs_argv[2],
+		     bs_argv[3], bs_argv[4], bs_argv[5]);
+	setcontext (&ctx);
+      }
+
+    /* get_context or setcontext failed;
+       Resort to using the conventional stack.  */
+}