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

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  • [AArch32,libgloss] Fix semihosting SYS_EXIT call on semihosting v1.
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Commit Message

Tamar Christina July 11, 2018, 12:39 p.m.
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

Comments

Corinna Vinschen July 11, 2018, 3:18 p.m. | #1
On Jul 11 12:39, Tamar Christina wrote:
> From 5c8c95cdf19602fb3ad569fbcbeda4ce5304b537 Mon Sep 17 00:00:00 2001

> From: Tamar Christina <tamar.christina@arm.com>

> 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 <tamar.christina@arm.com>

> ---

>  libgloss/arm/_kill.c | 6 ++++++

>  1 file changed, 6 insertions(+)


Pushed.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

Patch

From 5c8c95cdf19602fb3ad569fbcbeda4ce5304b537 Mon Sep 17 00:00:00 2001
From: Tamar Christina <tamar.christina@arm.com>
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 <tamar.christina@arm.com>
---
 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