[PATCH] Aarch64 SVE: Fix stack smashing when calling functions

[Alan Hayward <alan.hayward@arm.com>]

Using "call" on a function that passes arguments via float registers can cause
gdb to overflow buffers.

Ensure enough memory is reserved to hold a full FP register.

2018-09-17  Alan Hayward  <alan.hayward@arm.com>

	* aarch64-tdep.c (pass_in_v): Use register size.
	(aarch64_extract_return_value): Likewise.
	(aarch64_store_return_value): Likewise.
---
 gdb/aarch64-tdep.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 6993e9061e..516eb138dc 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -1358,7 +1358,10 @@ pass_in_v (struct gdbarch *gdbarch,
   if (info->nsrn < 8)
     {
       int regnum = AARCH64_V0_REGNUM + info->nsrn;
-      gdb_byte reg[V_REGISTER_SIZE];
+      /* Enough space for a full vector register.  */
+      gdb_byte reg[register_size (gdbarch, regnum)];
+      gdb_static_assert (AARCH64_V0_REGNUM == AARCH64_SVE_Z0_REGNUM);
+      gdb_assert (len <= sizeof (reg));
 
       info->argnum++;
       info->nsrn++;
@@ -1929,7 +1932,10 @@ aarch64_extract_return_value (struct type *type, struct regcache *regs,
       for (int i = 0; i < elements; i++)
 	{
 	  int regno = AARCH64_V0_REGNUM + i;
-	  bfd_byte buf[V_REGISTER_SIZE];
+	  /* Enough space for a full vector register.  */
+	  gdb_byte buf[register_size (gdbarch, regno)];
+	  gdb_static_assert (AARCH64_V0_REGNUM == AARCH64_SVE_Z0_REGNUM);
+	  gdb_assert (len <= sizeof (buf));
 
 	  if (aarch64_debug)
 	    {
@@ -2039,7 +2045,10 @@ aarch64_store_return_value (struct type *type, struct regcache *regs,
       for (int i = 0; i < elements; i++)
 	{
 	  int regno = AARCH64_V0_REGNUM + i;
-	  bfd_byte tmpbuf[V_REGISTER_SIZE];
+	  /* Enough space for a full vector register.  */
+	  gdb_byte tmpbuf[register_size (gdbarch, regno)];
+	  gdb_static_assert (AARCH64_V0_REGNUM == AARCH64_SVE_Z0_REGNUM);
+	  gdb_assert (len <= sizeof (tmpbuf));
 
 	  if (aarch64_debug)
 	    {
-- 
2.15.2 (Apple Git-101.1)