[Patch][newlib][arm] Enable return code with semi-hosting SYS_EXIT_EXTENDED

[Matthew Malcomson]

On 20/11/18 11:16, Richard Earnshaw (lists) wrote:
> On 16/11/2018 18:48, Matthew Malcomson wrote:
>> The _exit function currently passes -1 as a "sig" to the _kill function as an
>> invalid signal number so that _kill can distinguish between an abort and a
>> standard exit.
>>
>> For boards using the SYS_EXIT_EXTENDED semi-hosting operation to return a
>> status code, this means that the "status" paramter to _exit is ignored and the
>> return code is always -1.
>> https://developer.arm.com/docs/100863/latest/semihosting-operations/sys_exit_extended-0x20
>>
>> This patch puts shared code between _kill and _exit into a new function
>> _kill_shared that takes the semi-hosting "reason" to use (if semi-hosting is
>> available) as an argument.
>>
>> For semi-hosting _kill_shared provides that "reason".
>>
>> Without the "sig" argument being used to distinguish between a normal and
>> abnormal exit, the _exit function can provide the return code to be used if the
>> SYS_EXIT_EXTENDED operation is available.
>>
>> Hence the exit code can be returned.
>>
>> Tested with gcc testsuite on arm-none-eabi and no issues.
>> Ok for master?
>>
>> PS. I don't have commit rights so if OK can someone commit for me?
> This change needs to be applied to the similar code in newlib's sys
> directory as well.  PLEASE keep this in sync.
>
> R.
Thanks for pointing that out, and thanks for the help in testing too.
The patch applying this same change to the sys/ directory is attached.

If OK could someone commit for me? I don't have commit rights.

Regards,
Matthew


#### Patch inlined for ease of reply ###

diff --git a/newlib/libc/sys/arm/syscalls.c b/newlib/libc/sys/arm/syscalls.c
index 87ddca7..b521074 100644
--- a/newlib/libc/sys/arm/syscalls.c
+++ b/newlib/libc/sys/arm/syscalls.c
@@ -30,7 +30,7 @@ int    _stat        (const char *, struct stat *);
  int    _fstat        (int, struct stat *);
  void *    _sbrk        (ptrdiff_t);
  pid_t    _getpid        (void);
-int    _kill        (int, int) __attribute__((__noreturn__));
+int    _kill        (int, int);
  void    _exit        (int);
  int    _close        (int);
  int    _swiclose    (int);
@@ -49,6 +49,7 @@ static int    error        (int);
  static int    get_errno    (void);
  static int    remap_handle    (int);
  static int    findslot    (int);
+static int    _kill_shared    (int, int, int) 
__attribute__((__noreturn__));

  /* Register name faking - works in collusion with the linker.  */
  register char * stack_ptr asm ("sp");
@@ -424,21 +425,35 @@ _close (int file)
    return wrap (_swiclose (file));
  }

-int
-_kill (int pid, int sig)
+static int
+_kill_shared (int pid, int sig, int reason)
  {
-  (void)pid; (void)sig;
+  (void) pid; (void) sig;
  #ifdef ARM_RDI_MONITOR
    /* Note: The pid argument is thrown away.  */
-  switch (sig) {
-      case SIGABRT:
-          do_AngelSWI (AngelSWI_Reason_ReportException,
-                   (void *) ADP_Stopped_RunTimeError);
-          __builtin_unreachable();
-      default:
-          do_AngelSWI (AngelSWI_Reason_ReportException,
-                   (void *) ADP_Stopped_ApplicationExit);
-  }
+  int block[2];
+  block[1] = sig;
+  block[0] = reason;
+  int insn;
+
+#if SEMIHOST_V2
+  if (_has_ext_exit_extended ())
+    {
+      insn = AngelSWI_Reason_ReportExceptionExtended;
+    }
+  else
+#endif
+    {
+      insn = AngelSWI_Reason_ReportException;
+    }
+
+#if SEMIHOST_V2
+if (_has_ext_exit_extended ())
+  do_AngelSWI (insn, block);
+else
+#endif
+  do_AngelSWI (insn, (void*)block[0]);
+
  #else
    asm ("swi %a0" :: "i" (SWI_Exit));
  #endif
@@ -446,15 +461,24 @@ _kill (int pid, int sig)
    __builtin_unreachable();
  }

+int
+_kill (int pid, int sig)
+{
+  if (sig == SIGABRT)
+    _kill_shared (pid, sig, ADP_Stopped_RunTimeError);
+  else
+    _kill_shared (pid, sig, ADP_Stopped_ApplicationExit);
+}
+
  void
  _exit (int status)
  {
-  /* There is only one SWI for both _exit and _kill. For _exit, call
-     the SWI with the second argument set to -1, an invalid value for
-     signum, so that the SWI handler can distinguish the two calls.
-     Note: The RDI implementation of _kill throws away both its
-     arguments.  */
-  _kill(status, -1);
+  /* The same SWI is used for both _exit and _kill.
+     For _exit, call the SWI with "reason" set to 
ADP_Stopped_ApplicationExit
+     to mark a standard exit.
+     Note: The RDI implementation of _kill_shared throws away all its
+     arguments and all implementations ignore the first argument. */
+  _kill_shared (-1, status, ADP_Stopped_ApplicationExit);
  }

  pid_t
-- 
2.7.4



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