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

[Tamar Christina]

Hi All,

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

Cross compiled arm-none-eabi and regtested using check-gcc and no regressions.

Ok for master?

PS. I do not have commit rights so if OK can someone apply for me?

Thanks,
Tamar

[Corinna Vinschen]

From 5c8c95cdf19602fb3ad569fbcbeda4ce5304b537 Mon Sep 17 00:00:00 2001
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
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
---
libgloss/arm/_kill.c | 6 ++++++
1 file changed, 6 insertions(+)

Pushed.


Thanks,
Corinna