Add support for Semihosting v2 support for AArch64 in libgloss.

Semihosting v2 changes are documented here:
https://developer.arm.com/docs/100863/latest/

The biggest change is the addition of an extensions mechanism
to add more extensions in the future.

Signed-off-by: Tamar Christina <tamar.christina@arm.com>

libgloss/aarch64/_exit.c

@@ -36,6 +36,12 @@ _exit (int status)
       param_block_t block[2];
       block[0] = ADP_Stopped_ApplicationExit;
       block[1] = status;
+
+#if SEMIHOST_V2
+      if (_has_ext_exit_extended ())
+	 do_AngelSVC (AngelSVC_Reason_ReportExceptionExtended, block);
+      else
+#endif
 	 do_AngelSVC (AngelSVC_Reason_ReportException, block);
     }
 }

libgloss/aarch64/_kill.c

@@ -45,5 +45,11 @@ _kill (int pid, int sig)
 
   block[0] = ADP_Stopped_RunTimeError;
   block[1] = sig;
+
+#if SEMIHOST_V2
+  if (_has_ext_exit_extended ())
+    return do_AngelSVC (AngelSVC_Reason_ReportExceptionExtended, block);
+  else
+#endif
     return do_AngelSVC (AngelSVC_Reason_ReportException, block);
 }

libgloss/aarch64/svc.h

@@ -23,6 +23,8 @@
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
 
+#include <_ansi.h>
+
 /* Now the SWI numbers and reason codes for RDI (Angel) monitors.  */
 #define AngelSVC				0xF000
 #define AngelSVCInsn				"hlt"
@@ -36,6 +38,7 @@
 #define AngelSVC_Reason_Write			0x05
 #define AngelSVC_Reason_Read			0x06
 #define AngelSVC_Reason_ReadC			0x07
+#define AngelSVC_Reason_IsError			0x08
 #define AngelSVC_Reason_IsTTY			0x09
 #define AngelSVC_Reason_Seek			0x0A
 #define AngelSVC_Reason_FLen			0x0C
@@ -51,10 +54,29 @@
 #define AngelSVC_Reason_EnterSVC		0x17
 #define AngelSVC_Reason_ReportException 	0x18
 #define AngelSVC_Reason_SyncCacheRange		0x19
+#define AngelSVC_Reason_ReportExceptionExtended 0x20
 #define AngelSVC_Reason_Elapsed			0x30
+#define AngelSVC_Reason_TickFreq		0x31
 #define ADP_Stopped_ApplicationExit		((2 << 16) + 38)
 #define ADP_Stopped_RunTimeError		((2 << 16) + 35)
 
+/* Semihosting feature magic numbers.  */
+#define NUM_SHFB_MAGIC			4
+#define SHFB_MAGIC_0			0x53
+#define SHFB_MAGIC_1			0x48
+#define SHFB_MAGIC_2			0x46
+#define SHFB_MAGIC_3			0x42
+
+/* Semihosting extensions.  */
+#define SH_EXT_EXIT_EXTENDED_BITNUM	0x0
+#define SH_EXT_STDOUT_STDERR_BITNUM	0x1
+
+#if !defined (__ASSEMBLER__)
+extern int _get_semihosting_exts _PARAMS ((char*, int, int));
+extern int _has_ext_exit_extended _PARAMS ((void));
+extern int _has_ext_stdout_stderr _PARAMS ((void));
+#endif
+
 #if defined(ARM_RDI_MONITOR) && !defined(__ASSEMBLER__)
 
 /* Type of each entry in a parameter block.  */

libgloss/aarch64/syscalls.c

@@ -76,6 +76,9 @@ static int checkerror _PARAMS ((int));
 static int error _PARAMS ((int));
 static int get_errno _PARAMS ((void));
 
+/* Semihosting utilities.  */
+static void initialise_semihosting_exts _PARAMS ((void));
+
 /* Struct used to keep track of the file position, just so we
    can implement fseek(fh,x,SEEK_CUR).  */
 struct fdent
@@ -130,6 +133,9 @@ static int monitor_stdin;
 static int monitor_stdout;
 static int monitor_stderr;
 
+static int supports_ext_exit_extended = -1;
+static int supports_ext_stdout_stderr = -1;
+
 /* Return a pointer to the structure associated with
    the user file descriptor fd. */
 static struct fdent *
@@ -188,6 +194,11 @@ initialise_monitor_handles (void)
   block[1] = 0;			/* mode "r" */
   monitor_stdin = do_AngelSVC (AngelSVC_Reason_Open, block);
 
+  for (i = 0; i < MAX_OPEN_FILES; i++)
+    openfiles[i].handle = -1;;
+
+  if (_has_ext_stdout_stderr ())
+  {
     block[0] = POINTER_TO_PARAM_BLOCK_T (":tt");
     block[2] = 3;			/* length of filename */
     block[1] = 4;			/* mode "w" */
@@ -197,17 +208,18 @@ initialise_monitor_handles (void)
     block[2] = 3;			/* length of filename */
     block[1] = 8;			/* mode "a" */
     monitor_stderr = do_AngelSVC (AngelSVC_Reason_Open, block);
+  }
 
   /* If we failed to open stderr, redirect to stdout. */
   if (monitor_stderr == -1)
     monitor_stderr = monitor_stdout;
 
-  for (i = 0; i < MAX_OPEN_FILES; i++)
-    openfiles[i].handle = -1;
-
   openfiles[0].handle = monitor_stdin;
   openfiles[0].flags = _FREAD;
   openfiles[0].pos = 0;
+
+  if (_has_ext_stdout_stderr ())
+  {
     openfiles[1].handle = monitor_stdout;
     openfiles[0].flags = _FWRITE;
     openfiles[1].pos = 0;
@@ -215,6 +227,99 @@ initialise_monitor_handles (void)
     openfiles[0].flags = _FWRITE;
     openfiles[2].pos = 0;
   }
+}
+
+int
+_has_ext_exit_extended (void)
+{
+  if (supports_ext_exit_extended < 0)
+  {
+    initialise_semihosting_exts ();
+  }
+
+  return supports_ext_exit_extended;
+}
+
+int
+_has_ext_stdout_stderr (void)
+{
+  if (supports_ext_stdout_stderr < 0)
+  {
+    initialise_semihosting_exts ();
+  }
+
+  return supports_ext_stdout_stderr;
+}
+
+static void
+initialise_semihosting_exts (void)
+{
+  supports_ext_exit_extended = 0;
+  supports_ext_stdout_stderr = 1;
+
+#if SEMIHOST_V2
+  char features[1];
+  if (_get_semihosting_exts (features, 0, 1) > 0)
+  {
+     supports_ext_exit_extended
+       = features[0] & (1 << SH_EXT_EXIT_EXTENDED_BITNUM);
+     supports_ext_stdout_stderr
+       = features[0] & (1 << SH_EXT_STDOUT_STDERR_BITNUM);
+  }
+#endif
+}
+
+int
+_get_semihosting_exts (char* features, int offset, int num)
+{
+  int fd = _open (":semihosting-features", O_RDONLY);
+  memset (features, 0, num);
+
+  if (fd == -1)
+  {
+    return -1;
+  }
+
+  struct fdent *pfd;
+  pfd = findslot (fd);
+
+  param_block_t block[1];
+  block[0] = pfd->handle;
+
+  int len = do_AngelSVC (AngelSVC_Reason_FLen, block);
+
+  if (len < NUM_SHFB_MAGIC
+      || num > (len - NUM_SHFB_MAGIC))
+  {
+     _close (fd);
+     return -1;
+  }
+
+  char buffer[NUM_SHFB_MAGIC];
+  int n_read = _read (fd, buffer, NUM_SHFB_MAGIC);
+
+  if (n_read < NUM_SHFB_MAGIC
+      || buffer[0] != SHFB_MAGIC_0
+      || buffer[1] != SHFB_MAGIC_1
+      || buffer[2] != SHFB_MAGIC_2
+      || buffer[3] != SHFB_MAGIC_3)
+  {
+     _close (fd);
+     return -1;
+  }
+
+  if (_lseek (fd, offset, SEEK_CUR) < 0)
+  {
+     _close (fd);
+     return -1;
+  }
+
+  n_read = _read (fd, features, num);
+
+  _close (fd);
+
+  return checkerror (n_read);
+}
 
 static int
 get_errno (void)