arch/tile: Fix a couple of issues with the COMPAT code for TILE-Gx.

First, the siginfo preamble wasn't quite right; we need to indicate
that we are padding up to 4 ints of preamble for 64-bit code, and
then for compat mode we need to pad differently, using only 3 ints.

Second, the C ABI requires a save area of two registers, not two
pointers, since in compat mode we have 64-bit registers all of which
we need to save, even though we only have 32-bit VAs.

Signed-off-by: Chris Metcalf <[e-mail]>

arch/tile/include/arch/abi.h

···
  * The ABI requires callers to allocate a caller state save area of
  * this many bytes at the bottom of each stack frame.
  */
-#ifdef __tile__
-#define C_ABI_SAVE_AREA_SIZE (2 * __SIZEOF_POINTER__)
-#endif
+#define C_ABI_SAVE_AREA_SIZE (2 * (CHIP_WORD_SIZE() / 8))
 
 /**
  * The operand to an 'info' opcode directing the backtracer to not

arch/tile/include/asm/siginfo.h

···
 
 #define __ARCH_SI_TRAPNO
 
+#ifdef __LP64__
+# define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
+#endif
+
 #include <asm-generic/siginfo.h>
 
 /*

arch/tile/kernel/compat_signal.c

···
 	sigset_t	  uc_sigmask;	/* mask last for extensibility */
 };
 
+#define COMPAT_SI_PAD_SIZE	((SI_MAX_SIZE - 3 * sizeof(int)) / sizeof(int))
+
 struct compat_siginfo {
 	int si_signo;
 	int si_errno;
 	int si_code;
 
 	union {
-		int _pad[SI_PAD_SIZE];
+		int _pad[COMPAT_SI_PAD_SIZE];
 
 		/* kill() */
 		struct {