Add basic support for the QNX operating system

This change adds some special cases to allow libunwind to compile
for QNX.

* QNX's copy of <elf.h> and <link.h> reside in sys/ instead.  To deal
  with this, an AC_CHECK_HEADERS() was added to check for the files
  in both locations.
* Similarly, QNX does not have <endian.h>.  In cases where the file is
  not found, logic was added to refer to QNX-specific macros to determine
  endianness.
* The QCC compiler, which is a wrapper around GCC, cannot handle some
  standard GCC options.  Therefore, logic was added to check for QCC,
  and when it is found, to suppress the use of -lgcc, and to express the
  option -nostartfiles as -Wc,-nostartfiles instead, which is correctly
  passed on to the underlying GCC.
* Finally, the support file os-qnx.c was added, patterned after the existing
  os-*.c files.  Only local image lookup is currently supported (see the
  comments for more information), but this is sufficient for QNX, since
  ptrace is not supported there anyway, and that is the only case where the
  function is required to do remote image lookup.

Change-Id: Ie7934f94a7317bdde59335f2acd4c3a97c0384c1

1 files changed, 101 insertions, 0 deletions

diff --git a/src/os-qnx.c b/src/os-qnx.c
new file mode 100644
index 00000000..d01f920b
--- /dev/null
+++ b/src/os-qnx.c
@@ -0,0 +1,101 @@
+/* libunwind - a platform-independent unwind library
+   Copyright (C) 2013 Garmin International
+	Contributed by Matt Fischer <matt.fischer@garmin.com>
+
+This file is part of libunwind.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
+
+#include <string.h>
+
+#include "libunwind_i.h"
+
+struct cb_info
+{
+    unw_word_t ip;
+    unsigned long segbase;
+    unsigned long offset;
+    const char *path;
+};
+
+static int callback(const struct dl_phdr_info *info, size_t size, void *data)
+{
+  int i;
+  struct cb_info *cbi = (struct cb_info*)data;
+  for(i=0; i<info->dlpi_phnum; i++) {
+    int segbase = info->dlpi_addr + info->dlpi_phdr[i].p_vaddr;
+    if(cbi->ip >= segbase && cbi->ip < segbase + info->dlpi_phdr[i].p_memsz)
+    {
+      cbi->path = info->dlpi_name;
+      cbi->offset = info->dlpi_phdr[i].p_offset;
+      cbi->segbase = segbase;
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+PROTECTED int
+tdep_get_elf_image (struct elf_image *ei, pid_t pid, unw_word_t ip,
+                    unsigned long *segbase, unsigned long *mapoff,
+                    char *path, size_t pathlen)
+{
+  struct cb_info cbi;
+  int ret = -1;
+  cbi.ip = ip;
+  cbi.segbase = 0;
+  cbi.offset = 0;
+  cbi.path = NULL;
+
+  /* QNX's support for accessing symbol maps is severely broken.  There is a devctl() call that
+     can be made on a proc node (DCMD_PROC_MAPDEBUG) which returns information similar to Linux's
+     /proc/<pid>/maps node, however the filename that is returned by this call is not an absolute
+     path, and there is no foolproof way to map the filename back to the file that it came from.
+
+     Therefore, the normal approach for implementing this function, which works equally well for
+     both local and remote unwinding, will not work here.  The only type of image lookup which
+     works reliably is locally, using dl_iterate_phdr().  However, the only time that this function
+     is required to look up a remote image is for ptrace support, which doesn't work on QNX anyway.
+     Local unwinding, which is the main case that makes use of this function, will work fine with
+     dl_iterate_phdr().  Therefore, in lieu of any better platform support for remote image lookup,
+     this function has just been implemented in terms of dl_iterate_phdr().
+  */
+  if (pid != getpid())
+  {
+    /* Return an error if an attempt is made to perform remote image lookup */
+    return -1;
+  }
+
+  if (dl_iterate_phdr (callback, &cbi) != 0)
+  {
+    if (path)
+    {
+      strncpy (path, cbi.path, pathlen);
+    }
+
+    *mapoff = cbi.offset;
+    *segbase = cbi.segbase;
+
+    ret = elf_map_image (ei, cbi.path);
+  }
+
+  return ret;
+}