* sparc-tdep.c (sparc_fetch_wcookie): New function.

(sparc32_frame_prev_register): Handle StackGhost.
(sparc_supply_rwindow, sparc_collect_rwindow): Likewise.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ade8531..720dc80 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2004-01-31  Mark Kettenis  <kettenis@gnu.org>
+
+       * sparc-tdep.c (sparc_fetch_wcookie): New function.
+       (sparc32_frame_prev_register): Handle StackGhost.
+       (sparc_supply_rwindow, sparc_collect_rwindow): Likewise.
+
 2004-01-29  Roland McGrath  <roland@redhat.com>
 
        * configure.in (NEW_PROC_API): Also match solaris2.9 for this test.

diff --git a/gdb/sparc-tdep.c b/gdb/sparc-tdep.c
index f8adccc..1719109 100644 (file)
--- a/gdb/sparc-tdep.c
+++ b/gdb/sparc-tdep.c
@@ -106,6 +106,48 @@ sparc_fetch_instruction (CORE_ADDR pc)
   return insn;
 }
 \f
+
+/* OpenBSD/sparc includes StackGhost, which according to the author's
+   website http://stackghost.cerias.purdue.edu "... transparently and
+   automatically protects applications' stack frames; more
+   specifically, it guards the return pointers.  The protection
+   mechanisms require no application source or binary modification and
+   imposes only a negligible performance penalty."
+
+   The same website provides the following description of how
+   StackGhost works:
+
+   "StackGhost interfaces with the kernel trap handler that would
+   normally write out registers to the stack and the handler that
+   would read them back in.  By XORing a cookie into the
+   return-address saved in the user stack when it is actually written
+   to the stack, and then XOR it out when the return-address is pulled
+   from the stack, StackGhost can cause attacker corrupted return
+   pointers to behave in a manner the attacker cannot predict.
+   StackGhost can also use several unused bits in the return pointer
+   to detect a smashed return pointer and abort the process."
+
+   For GDB this means that whenever we're reading %i7 from a stack
+   frame's window save area, we'll have to XOR the cookie.
+
+   More information on StackGuard can be found on in:
+
+   Mike Frantzen and Mike Shuey. "StackGhost: Hardware Facilitated
+   Stack Protection."  2001.  Published in USENIX Security Symposium
+   '01.  */
+
+/* Fetch StackGhost Per-Process XOR cookie.  */
+
+ULONGEST
+sparc_fetch_wcookie (void)
+{
+  /* FIXME: kettenis/20040131: We should fetch the cookie from the
+     target.  For now, return zero, which is right for targets without
+     StackGhost.  */
+  return 0;
+}
+
+\f
 /* Return the contents if register REGNUM as an address.  */
 
 static CORE_ADDR
@@ -666,6 +708,29 @@ sparc32_frame_prev_register (struct frame_info *next_frame, void **this_cache,
       return;
     }
 
+  /* Handle StackGhost.  */
+  {
+    ULONGEST wcookie = sparc_fetch_wcookie ();
+
+    if (wcookie != 0 && !cache->frameless_p && regnum == SPARC_I7_REGNUM)
+      {
+       *optimizedp = 0;
+       *lvalp = not_lval;
+       *addrp = 0;
+       *realnump = -1;
+       if (valuep)
+         {
+           CORE_ADDR addr = cache->base + (regnum - SPARC_L0_REGNUM) * 4;
+           ULONGEST i6;
+
+           /* Read the value in from memory.  */
+           i6 = get_frame_memory_unsigned (next_frame, addr, 4);
+           store_unsigned_integer (valuep, 4, i6 ^ wcookie);
+         }
+       return;
+      }
+  }
+
   /* The previous frame's `local' and `in' registers have been saved
      in the register save area.  */
   if (!cache->frameless_p
@@ -1163,6 +1228,16 @@ sparc_supply_rwindow (struct regcache *regcache, CORE_ADDR sp, int regnum)
            {
              target_read_memory (sp + ((i - SPARC_L0_REGNUM) * 4),
                                  buf + offset, 4);
+
+             /* Handle StackGhost.  */
+             if (i == SPARC_I7_REGNUM)
+               {
+                 ULONGEST wcookie = sparc_fetch_wcookie ();
+                 ULONGEST i6 = extract_unsigned_integer (buf + offset, 4);
+
+                 store_unsigned_integer (buf + offset, 4, i6 ^ wcookie);
+               }
+
              regcache_raw_supply (regcache, i, buf);
            }
        }
@@ -1206,6 +1281,16 @@ sparc_collect_rwindow (const struct regcache *regcache,
          if (regnum == -1 || regnum == SPARC_SP_REGNUM || regnum == i)
            {
              regcache_raw_collect (regcache, i, buf);
+
+             /* Handle StackGhost.  */
+             if (i == SPARC_I7_REGNUM)
+               {
+                 ULONGEST wcookie = sparc_fetch_wcookie ();
+                 ULONGEST i6 = extract_unsigned_integer (buf + offset, 4);
+
+                 store_unsigned_integer (buf + offset, 4, i6 ^ wcookie);
+               }
+
              target_write_memory (sp + ((i - SPARC_L0_REGNUM) * 4),
                                   buf + offset, 4);
            }