[PATCH] alpha: Use ssize_t to allocate space on stack

[Siddhesh Poyarekar <siddhesh@redhat.com>]

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Hi,

This is again an independent portion of the bitpos patch[1].  The
variables used to set up the stack are currently int, which may not be
sufficient for larger types.  This patch expands the variable sizes to
ssize_t.  The patch also adds an additional validation to check for
underflow in the value of the stack pointer after pushing the
arguments.  I don't have any means to run any tests, so I have only
done a compile test for this by configuring with --enable-targets=all.
Does this look safe for commit?

Regards,
Siddhesh

[1] http://sourceware.org/ml/gdb-patches/2012-08/msg00144.html

gdb/ChangeLog:

	* alpha-tdep.c (alpha_push_dummy_call): Expand ACCUMULATE_SIZE,
	REQUIRED_ARG_REGS, OFFSET, LEN, TLEN to ssize_t.  Check for
	underflow in SP.
	(struct alpha_arg): Expand members LEN, OFFSET to ssize_t.

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Index: gdb/alpha-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/alpha-tdep.c,v
retrieving revision 1.212
diff -u -r1.212 alpha-tdep.c
--- gdb/alpha-tdep.c	25 Sep 2012 12:48:52 -0000	1.212
+++ gdb/alpha-tdep.c	25 Sep 2012 15:21:46 -0000
@@ -299,18 +299,18 @@
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
   int i;
-  int accumulate_size = struct_return ? 8 : 0;
+  ssize_t accumulate_size = struct_return ? 8 : 0;
   struct alpha_arg
     {
       const gdb_byte *contents;
-      int len;
-      int offset;
+      ssize_t len;
+      ssize_t offset;
     };
   struct alpha_arg *alpha_args
     = (struct alpha_arg *) alloca (nargs * sizeof (struct alpha_arg));
   struct alpha_arg *m_arg;
   gdb_byte arg_reg_buffer[ALPHA_REGISTER_SIZE * ALPHA_NUM_ARG_REGS];
-  int required_arg_regs;
+  ssize_t required_arg_regs;
   CORE_ADDR func_addr = find_function_addr (function, NULL);
 
   /* The ABI places the address of the called function in T12.  */
@@ -414,6 +414,13 @@
     accumulate_size = 0;
   else
     accumulate_size -= sizeof(arg_reg_buffer);
+
+  /* Check for underflow.  */
+  if (sp - accumulate_size > sp)
+    error (_("Insufficient memory in GDB host for arguments, "
+	     "need %s bytes, but less than %s bytes available."),
+	   plongest (accumulate_size), plongest (CORE_ADDR_MAX - sp));
+
   sp -= accumulate_size;
 
   /* Keep sp aligned to a multiple of 16 as the ABI requires.  */
@@ -423,8 +430,8 @@
   for (i = nargs; m_arg--, --i >= 0;)
     {
       const gdb_byte *contents = m_arg->contents;
-      int offset = m_arg->offset;
-      int len = m_arg->len;
+      ssize_t offset = m_arg->offset;
+      ssize_t len = m_arg->len;
 
       /* Copy the bytes destined for registers into arg_reg_buffer.  */
       if (offset < sizeof(arg_reg_buffer))
@@ -436,7 +443,7 @@
 	    }
 	  else
 	    {
-	      int tlen = sizeof(arg_reg_buffer) - offset;
+	      ssize_t tlen = sizeof(arg_reg_buffer) - offset;
 	      memcpy (arg_reg_buffer + offset, contents, tlen);
 	      offset += tlen;
 	      contents += tlen;