[PATCH][AArch32][libgloss] Fix semihosting SYS_EXIT call on semihosting v1.

From 5c8c95cdf19602fb3ad569fbcbeda4ce5304b537 Mon Sep 17 00:00:00 2001
From: Tamar Christina <[email protected]>
Date: Wed, 11 Jul 2018 13:26:16 +0100
Subject: [PATCH] Fix AArch32 semihosting SYS_EXIT call on semihosting v1.

The current SYS_EXIT has a bug that when making the call it always uses
the v2 calling convention.  This is undefined behavior according to the
semihosting specification:
https://developer.arm.com/docs/100863/latest/semihosting-operations/sys_exit-0x18

This patch fixes it by making sure v1 passes the argument directly in the register instead
of in a block. And for v2 it does the same if the v2 extension isn't supported.

The sequence generated now is

   12424:       ebfffecd        bl      11f60 <_has_ext_exit_extended>
   12428:       e3500000        cmp     r0, #0
   1242c:       11a0500d        movne   r5, sp
   12430:       059d5000        ldreq   r5, [sp]
   12434:       e1a00004        mov     r0, r4
   12438:       e1a01005        mov     r1, r5
   1243c:       ef00f000        svc     0x0000f000

Signed-off-by: Tamar Christina <[email protected]>
---
 libgloss/arm/_kill.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libgloss/arm/_kill.c b/libgloss/arm/_kill.c
index fc77e8097..278ded73a 100644
--- a/libgloss/arm/_kill.c
+++ b/libgloss/arm/_kill.c
@@ -39,7 +39,13 @@ _kill (int pid, int sig)
       }
     }
 
+#if SEMIHOST_V2
+if (_has_ext_exit_extended ())
   return do_AngelSWI (insn, block);
+else
+#endif
+  return do_AngelSWI (insn, (void*)block[0]);
+
 #else
   asm ("swi %a0" :: "i" (SWI_Exit));
 #endif
-- 
2.17.1