linux: use /proc/self/maps to find precise stack base

src/racket/sconfig.h

@@ -203,6 +203,7 @@
 # define SIGSET_IS_SIGNAL
 # define SIGSET_NEEDS_REINSTALL
 
+# define LINUX_FIND_STACK_BASE
 # define USE_DYNAMIC_FDSET_SIZE
 
 # define USE_TIMEZONE_VAR_W_DLS
@@ -1307,6 +1308,9 @@
     WINDOWS_FIND_STACK_BOUNDS figures out the maximum stack position
      under Windows (uses GC_find_stack_base())
     MACOS_FIND_STACK_BOUNDS figures out the stack limit on the Mac.
+    LINUX_FIND_STACK_BASE figures out the stack base under Linux
+     by reading from /proc/self/maps and looking for "[stack]"
+     line.
     ASSUME_FIXED_STACK_SIZE assumes that the main stack size is
      always FIXED_STACK_SIZE.
     Use only one of these if DO_STACK_CHECK is used, or none otherwise. */

src/racket/src/eval.c

@@ -426,6 +426,54 @@ scheme_handle_stack_overflow(Scheme_Object *(*k)(void))
   return NULL; /* never gets here */
 }
 
+#ifdef LINUX_FIND_STACK_BASE
+uintptr_t adjust_stack_base(uintptr_t bnd) {
+  if (bnd == scheme_get_primordial_thread_stack_base()) {
+    /* The address `base' might be far from the actual stack base
+       if Exec Sheild is enabled. Use "/proc/self/maps" to get 
+       exacty the stack base. */
+    FILE *f;
+    char *buf;
+    f = fopen("/proc/self/maps", "r");
+    if (f) {
+      buf = malloc(256);
+      while (fgets(buf, 256, f)) {
+	int len;
+	len = strlen(buf);
+	if ((len > 8) && !strcmp("[stack]\n", buf + len - 8)) {
+	  uintptr_t p = 0;
+	  int i;
+	  /* find separator: */
+	  for (i = 0; buf[i]; i++) {
+	    if (buf[i] == '-') {
+	      i++;
+	      break;
+	    }
+	  }
+	  /* parse number after separator: */
+	  for (; buf[i]; i++) {
+	    if ((buf[i] >= '0') && (buf[i] <= '9')) {
+	      p = (p << 4) | (buf[i] - '0');
+	    } else if ((buf[i] >= 'a') && (buf[i] <= 'f')) {
+	      p = (p << 4) | (buf[i] - 'a' + 10);
+	    } else if ((buf[i] >= 'A') && (buf[i] <= 'F')) {
+	      p = (p << 4) | (buf[i] - 'A' + 10);
+	    } else
+	      break;
+	  }
+	  /* printf("%p vs. %p: %d\n", (void*)bnd, (void*)p, p - bnd); */
+	  return p;
+	}
+      }
+      free(buf);
+      fclose(f);
+    }
+  }
+
+  return bnd;
+}
+#endif
+
 void scheme_init_stack_check()
      /* Finds the C stack limit --- platform-specific. */
 {
@@ -503,6 +551,10 @@ void scheme_init_stack_check()
       uintptr_t bnd, lim;
       bnd = (uintptr_t)scheme_get_current_os_thread_stack_base();
 
+#  ifdef LINUX_FIND_STACK_BASE
+      bnd = adjust_stack_base(bnd);
+#  endif
+
       lim = (uintptr_t)rl.rlim_cur;
 #  ifdef UNIX_STACK_MAXIMUM
       if (lim > UNIX_STACK_MAXIMUM)

src/racket/src/salloc.c

@@ -74,7 +74,7 @@ int scheme_thread_local_offset = 0;
 #endif
 
 extern int scheme_num_copied_stacks;
-SHARED_OK static uintptr_t scheme_primordial_os_thread_stack_base;
+SHARED_OK static uintptr_t primordial_os_thread_stack_base;
 THREAD_LOCAL_DECL(static uintptr_t scheme_os_thread_stack_base);
 #ifdef USE_THREAD_LOCAL
 SHARED_OK Thread_Local_Variables *scheme_vars; /* for debugging */
@@ -118,7 +118,7 @@ void scheme_set_stack_base(void *base, int no_auto_statics) XFORM_SKIP_PROC
   scheme_register_traversers();
 #endif
 
-  scheme_primordial_os_thread_stack_base  = (uintptr_t) base;
+  primordial_os_thread_stack_base = (uintptr_t) base;
   scheme_os_thread_stack_base     = (uintptr_t) base;
 
 #if defined(MZ_PRECISE_GC) || defined(USE_SENORA_GC)
@@ -152,6 +152,11 @@ uintptr_t scheme_get_current_os_thread_stack_base()
   return scheme_os_thread_stack_base;
 }
 
+uintptr_t scheme_get_primordial_thread_stack_base()
+{
+  return primordial_os_thread_stack_base;
+}
+
 typedef struct {
   Scheme_Env_Main _main;
   int argc;

src/racket/src/schpriv.h

@@ -130,7 +130,8 @@ int scheme_num_types(void);
 
 void scheme_reset_finalizations(void);
 
-extern uintptr_t scheme_get_current_os_thread_stack_base(void);
+uintptr_t scheme_get_primordial_thread_stack_base(void);
+uintptr_t scheme_get_current_os_thread_stack_base(void);
 void scheme_set_current_os_thread_stack_base(void *base);
 
 int scheme_propagate_ephemeron_marks(void);