[patch 3/4] unwinder: Provide dwfl_core_filename_report

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

dependent on:
	[patch 2/4] unwinder: Provide EBLHOOKVAR

present in:
	jankratochvil/forunwind-baseaddr-hookvars-corereport
but this branch is not suitable for merge as it is unclear in which form get
checked in the patches above.  The branch is usable only for "git checkout",
neither diff nor merge should be done on it.


Currently dwfl_core_file_report requires Elf *core.  But application cannot
open Elf * on its own, it is elfutils internal function.  Various workarounds
I have tried in the code below (the last one works but it is ugly):


#if 0
  /* FIXME: Here COREFILE gets errorneously reported into VMA of DWFL.  */
  Dwfl_Module *mod = dwfl_report_elf (dwfl, "core", corefile, -1, 0 /* base */);
  assert (mod != NULL);
  Elf *core = dwfl_module_getelf (mod, NULL);
  assert (core != NULL);
  int result = dwfl_core_file_report (dwfl, core);
  assert (result >= 0);
#endif
#if 0
  /* FIXME: Here it does not build as __libdw_open_file is private.  */
  int core_fd = open64 (corefile, O_RDONLY);
  assert (core_fd >= 0);
  Elf *core;
  Dwfl_Error err = __libdw_open_file (&core_fd, &core, true, false);
  assert (err == DWFL_E_NOERROR);
  int result = dwfl_core_file_report (dwfl, core);
  assert (result >= 0);
  result = elf_end (core);
  assert (result == 0);
  result = close (core_fd);
  assert (result == 0);
#endif
#if 1
  /* FIXME: Here we use different DWFL, reported data would be used after free
     if we called dwfl_end (core_dwfl).  Therefore we leak CORE_DWFL.  */
  Dwfl *core_dwfl = dwfl_offline ();
  Dwfl_Module *mod = dwfl_report_elf (core_dwfl, "core", corefile, -1,
                                     0 /* base */);
  assert (mod != NULL);
  GElf_Addr loadbase_ignore;
  Elf *core = dwfl_module_getelf (mod, &loadbase_ignore);
  assert (core != NULL);
  int result = dwfl_core_file_report (dwfl, core);
  assert (result >= 0);
  // dwfl_end (core_dwfl);
#endif


It is also already suspicious why libdwfl/argp-std.c is using elfutils
internal function, application should be able to implement parsing commandline
parameters on its own.


Thanks,
Jan


libdw/
2012-11-13  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* libdw.map (ELFUTILS_0.156): New block.

libdwfl/
2012-11-13  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* argp-std.c (parse_opt): Remove label nofile.  Substitute code by
	a dwfl_core_filename_report call.  Initialize error from dwfl_errno
	now.  Check dwfl->modulelist instead of former RESULT.
	* core-file.c: Include fcntl.h.
	(dwfl_core_filename_report): New function.
	* libdwfl.h (dwfl_core_filename_report): New declaration.

diff --git a/libdw/libdw.map b/libdw/libdw.map
index 1f71d03..5a055e8 100644
--- a/libdw/libdw.map
+++ b/libdw/libdw.map
@@ -254,3 +254,8 @@ ELFUTILS_0.149 {
 
     dwfl_dwarf_line;
 } ELFUTILS_0.148;
+
+ELFUTILS_0.156 {
+  global:
+    dwfl_core_filename_report;
+} ELFUTILS_0.149;
diff --git a/libdwfl/argp-std.c b/libdwfl/argp-std.c
index f0c530f..8aeb80a 100644
--- a/libdwfl/argp-std.c
+++ b/libdwfl/argp-std.c
@@ -205,7 +205,6 @@ parse_opt (int key, char *arg, struct argp_state *state)
 	  {
 	    FILE *f = fopen (arg, "r");
 	    if (f == NULL)
-	    nofile:
 	      {
 		int code = errno;
 		argp_failure (state, EXIT_FAILURE, code,
@@ -291,31 +290,18 @@ parse_opt (int key, char *arg, struct argp_state *state)
 
 	if (opt->core)
 	  {
-	    int fd = open64 (opt->core, O_RDONLY);
-	    if (fd < 0)
-	      goto nofile;
-
-	    Elf *core;
-	    Dwfl_Error error = __libdw_open_file (&fd, &core, true, false);
-	    if (error != DWFL_E_NOERROR)
+	    if (dwfl_core_filename_report (dwfl, NULL, opt->core) == NULL)
 	      {
+		Dwfl_Error error = dwfl_errno ();
 		argp_failure (state, EXIT_FAILURE, 0,
 			      _("cannot read ELF core file: %s"),
 			      INTUSE(dwfl_errmsg) (error));
 		return error == DWFL_E_ERRNO ? errno : EIO;
 	      }
 
-	    int result = INTUSE(dwfl_core_file_report) (dwfl, core);
-	    if (result < 0)
-	      {
-		elf_end (core);
-		close (fd);
-		return fail (dwfl, result, opt->core);
-	      }
-
 	    /* From now we leak FD and CORE.  */
 
-	    if (result == 0)
+	    if (dwfl->modulelist == NULL)
 	      {
 		argp_failure (state, EXIT_FAILURE, 0,
 			      _("No modules recognized in core file"));
diff --git a/libdwfl/core-file.c b/libdwfl/core-file.c
index 1545ca8..f217847 100644
--- a/libdwfl/core-file.c
+++ b/libdwfl/core-file.c
@@ -37,6 +37,7 @@
 #include <endian.h>
 #include <byteswap.h>
 #include "system.h"
+#include <fcntl.h>
 
 
 /* This is a prototype of what a new libelf interface might be.
@@ -461,3 +462,39 @@ dwfl_core_file_report (Dwfl *dwfl, Elf *elf)
   return sniffed == 0 || listed > sniffed ? listed : sniffed;
 }
 INTDEF (dwfl_core_file_report)
+
+Elf *
+dwfl_core_filename_report (Dwfl *dwfl, int *fdp, const char *filename)
+{
+  int fd_storage = -1;
+  if (fdp == NULL)
+    fdp = &fd_storage;
+
+  if (*fdp < 0)
+    {
+      *fdp = open64 (filename, O_RDONLY);
+      if (*fdp < 0)
+	{
+	  __libdwfl_seterrno (DWFL_E_ERRNO);
+	  return NULL;
+	}
+    }
+
+  Elf *core;
+  Dwfl_Error error = __libdw_open_file (fdp, &core, true, false);
+  if (error != DWFL_E_NOERROR)
+    {
+      __libdwfl_seterrno (error);
+      return NULL;
+    }
+
+  int result = INTUSE(dwfl_core_file_report) (dwfl, core);
+  if (result < 0)
+    {
+      elf_end (core);
+      close (*fdp);
+      return NULL;
+    }
+  return core;
+}
+INTDEF (dwfl_core_filename_report)
diff --git a/libdwfl/libdwfl.h b/libdwfl/libdwfl.h
index a2ab824..c2b85f4 100644
--- a/libdwfl/libdwfl.h
+++ b/libdwfl/libdwfl.h
@@ -355,6 +355,14 @@ extern int dwfl_linux_kernel_report_offline (Dwfl *dwfl, const char *release,
    Returns the number of modules reported, or -1 for errors.  */
 extern int dwfl_core_file_report (Dwfl *dwfl, Elf *elf);
 
+/* Call dwfl_core_file_report but providing FILENAME instead.  Function returns
+   opened core file Elf * and its *FDP file descriptor which must be held valid
+   until dwfl_end is called for DWFL.  FDP can be passed as NULL (but the
+   caller cannot close the file descriptor then).  Function returns NULL for
+   errors, check dwfl_errmsg in such case.  */
+extern Elf *dwfl_core_filename_report (Dwfl *dwfl, int *fdp,
+				       const char *filename);
+
 /* Call dwfl_report_module for each file mapped into the address space of PID.
    Returns zero on success, -1 if dwfl_report_module failed,
    or an errno code if opening the kernel binary failed.  */