[PATCH] target_read_aux_vector

[Roland McGrath <roland at redhat dot com>]

This patch adds target_read_aux_vector to read the auxv information as a
whole block (there is no code here that interprets its contents).  It also
makes ELF core file writing (gcore) use this to produce an NT_AUXV note.
I have only tested the linux-proc.c code in actuality, but the procfs.c
(Solaris) and corelow.c code is so simple it would be hard for it to be
wrong.

The function signature used here is a little goofy if you ask me.  But I
modelled it on target_make_corefile_notes, which is another recent addition
and so I assume it is in the style that gdb folk prefer.  I would be happy
to change the signature if there is a different preference.  I made the
malloc'd-ness of the returned pointer part of the interface rather than
having it call make_cleanup and magically know that's the right scope as
the to_make_corefile_notes implementations do.

The one way I've tested this is that "gcore" used on Linux 2.6 du jour
produces an NT_AUXV note in the core file matching what a kernel-written
dump has.  The Solaris additions should make it do the same there as well.

The core_ops implementation of target_read_aux_vector is not presently
used at all, because you can't do gcore when examining a core file.
(Incidentally, I think gdb should support that.  Doing that and comparing
what gdb wrote to the original core file is a good test of both core file
reading and core file writing.)  It would be used by the tdep code looking
for AT_SYSINFO_EHDR, as we have been discussing here.

I am not happy that the identical function is duplicated in procfs.c and
linux-proc.c; but I did not see any place for common code that is usable
for both flavors of /proc filesystem.  The to_make_corefile_notes hooks in
those two files are close to identical as well.


Comments?


Thanks,
Roland


2003-10-06  Roland McGrath  <roland@redhat.com>

	* target.h (struct target_ops): New field `to_read_aux_vector'.
	(target_read_aux_vector): New macro.
	* target.c (update_current_target): Do INHERIT for to_read_aux_vector.
	(dummy_read_aux_vector): New function.
	(init_dummy_target): Initialize dummy_target.to_read_aux_vector.
	* inftarg.c (inftarg_set_read_aux_vector): New function.
	* linux-proc.c (procfs_read_aux_vector): New function.
	(_initialize_linux_proc): Call inftarg_set_read_aux_vector.
	(linux_make_note_section): Add an NT_AUXV note.
	* procfs.c (procfs_read_aux_vector): New function.
	(init_procfs_ops): Initialize procfs_ops.to_read_aux_vector.
	(procfs_make_note_section): Add an NT_AUXV note.
	* sol-thread.c (sol_read_aux_vector): New function.
	(init_sol_thread_ops): Initialize sol_thread_ops.to_read_aux_vector.
	* corelow.c (core_read_aux_vector): New function.
	(init_core_ops): Initialize core_ops.to_read_aux_vector.

Index: target.c
===================================================================
RCS file: /cvs/src/src/gdb/target.c,v
retrieving revision 1.55
diff -b -p -u -r1.55 target.c
--- target.c	2 Oct 2003 20:28:30 -0000	1.55
+++ target.c	7 Oct 2003 01:20:30 -0000
@@ -624,6 +624,7 @@ update_current_target (void)
       INHERIT (to_async, t);
       INHERIT (to_async_mask_value, t);
       INHERIT (to_find_memory_regions, t);
+      INHERIT (to_read_aux_vector, t);
       INHERIT (to_make_corefile_notes, t);
       INHERIT (to_get_thread_local_address, t);
       INHERIT (to_magic, t);
@@ -1500,6 +1501,13 @@ static int dummy_find_memory_regions (in
   return 0;
 }
 
+/* Error-catcher for target_read_aux_vector */
+static char *dummy_read_aux_vector (int *ignore1)
+{
+  error ("No target.");
+  return NULL;
+}
+
 /* Error-catcher for target_make_corefile_notes */
 static char * dummy_make_corefile_notes (bfd *ignore1, int *ignore2)
 {
@@ -1521,6 +1529,7 @@ init_dummy_target (void)
   dummy_target.to_pid_to_str = normal_pid_to_str;
   dummy_target.to_stratum = dummy_stratum;
   dummy_target.to_find_memory_regions = dummy_find_memory_regions;
+  dummy_target.to_read_aux_vector = dummy_read_aux_vector;
   dummy_target.to_make_corefile_notes = dummy_make_corefile_notes;
   dummy_target.to_magic = OPS_MAGIC;
 }
Index: target.h
===================================================================
RCS file: /cvs/src/src/gdb/target.h,v
retrieving revision 1.41
diff -b -p -u -r1.41 target.h
--- target.h	17 Jun 2003 20:28:13 -0000	1.41
+++ target.h	7 Oct 2003 01:20:30 -0000
@@ -322,6 +322,7 @@ struct target_ops
 					    int, int, int, 
 					    void *), 
 				   void *);
+    char *(*to_read_aux_vector) (int *);
     char * (*to_make_corefile_notes) (bfd *, int *);
 
     /* Return the thread-local address at OFFSET in the
@@ -939,6 +940,14 @@ extern void (*target_new_objfile_hook) (
      (current_target.to_find_memory_regions) (FUNC, DATA)
 
 /*
+ * Function to read target startup auxilliary vector (ELF-specific).
+ * Returns a malloc'd buffer of ELF auxv data, and sets *LENP to its size.
+ */
+
+#define target_read_aux_vector(LENP) \
+     (current_target.to_read_aux_vector) (LENP)
+
+/*
  * Compose corefile .note section.
  */
 
Index: inftarg.c
===================================================================
RCS file: /cvs/src/src/gdb/inftarg.c,v
retrieving revision 1.18
diff -b -p -u -r1.18 inftarg.c
--- inftarg.c	21 Sep 2003 01:26:45 -0000	1.18
+++ inftarg.c	7 Oct 2003 01:20:30 -0000
@@ -628,6 +628,13 @@ inftarg_set_find_memory_regions (int (*f
   child_ops.to_find_memory_regions = func;
 }
 
+/* Take over the 'read_aux_vector' vector from inftarg.c. */
+void
+inftarg_set_read_aux_vector (char *(*func) (int *))
+{
+  child_ops.to_read_aux_vector = func;
+}
+
 /* Take over the 'make_corefile_notes' vector from inftarg.c. */
 extern void 
 inftarg_set_make_corefile_notes (char * (*func) (bfd *, int *))
Index: linux-proc.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-proc.c,v
retrieving revision 1.20
diff -b -p -u -r1.20 linux-proc.c
--- linux-proc.c	1 Oct 2003 20:36:56 -0000	1.20
+++ linux-proc.c	7 Oct 2003 01:20:31 -0000
@@ -161,6 +161,46 @@ linux_find_memory_regions (int (*func) (
   return 0;
 }
 
+static char *
+procfs_read_aux_vector (int *lenp)
+{
+  char pathname[MAXPATHLEN];
+  int fd;
+  char *buf, *p;
+  int bufsz, n;
+
+  sprintf (pathname, "/proc/%d/auxv", PIDGET (inferior_ptid));
+  fd = open (pathname, O_RDONLY);
+  if (fd < 0)
+    return NULL;		/* XXX Call error here? */
+
+  bufsz = 256;
+  buf = (char *) xmalloc (bufsz);
+  p = buf;
+  while (1)
+    {
+      n = read (fd, p, buf + bufsz - p);
+      if (n == 0)		/* Hit EOF.  */
+	{
+	  *lenp = p - buf;
+	  break;
+	}
+      if (n < 0)		/* Read error.  */
+	{
+	  xfree (buf);
+	  buf = NULL;
+	  break;
+	}
+      bufsz *= 2;
+      n = p + n - buf;
+      buf = (char *) xrealloc (buf, bufsz);
+      p = buf + n;
+    }
+
+  close (fd);
+  return buf;
+}
+
 /* Function: linux_do_thread_registers
  *
  * Records the thread's register state for the corefile note section.
@@ -271,6 +311,8 @@ linux_make_note_section (bfd *obfd, int 
   char psargs[80] = { '\0' };
   char *note_data = NULL;
   ptid_t current_ptid = inferior_ptid;
+  char *auxv;
+  int auxv_len;
 
   if (get_exec_file (0))
     {
@@ -305,6 +347,14 @@ linux_make_note_section (bfd *obfd, int 
       note_data = thread_args.note_data;
     }
 
+  auxv = target_read_aux_vector (&auxv_len);
+  if (auxv != NULL)
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size,
+				      "CORE", NT_AUXV, auxv, auxv_len);
+      xfree (auxv);
+    }
+
   make_cleanup (xfree, note_data);
   return note_data;
 }
@@ -593,9 +643,11 @@ _initialize_linux_proc (void)
 {
   extern void inftarg_set_find_memory_regions ();
   extern void inftarg_set_make_corefile_notes ();
+  extern void inftarg_set_read_aux_vector ();
 
   inftarg_set_find_memory_regions (linux_find_memory_regions);
   inftarg_set_make_corefile_notes (linux_make_note_section);
+  inftarg_set_read_aux_vector (procfs_read_aux_vector);
 
   add_info ("proc", linux_info_proc_cmd,
 	    "Show /proc process information about any running process.\n\
Index: procfs.c
===================================================================
RCS file: /cvs/src/src/gdb/procfs.c,v
retrieving revision 1.48
diff -b -p -u -r1.48 procfs.c
--- procfs.c	21 Sep 2003 01:26:45 -0000	1.48
+++ procfs.c	7 Oct 2003 01:20:31 -0000
@@ -139,6 +139,7 @@ static int proc_find_memory_regions (int
 					      void *), 
 				     void *);
 
+static char *procfs_read_aux_vector (int *);
 static char * procfs_make_note_section (bfd *, int *);
 
 static int procfs_can_use_hw_breakpoint (int, int, int);
@@ -190,6 +191,7 @@ init_procfs_ops (void)
   procfs_ops.to_stratum             = process_stratum;
   procfs_ops.to_has_thread_control  = tc_schedlock;
   procfs_ops.to_find_memory_regions = proc_find_memory_regions;
+  procfs_ops.to_read_aux_vector     = procfs_read_aux_vector;
   procfs_ops.to_make_corefile_notes = procfs_make_note_section;
   procfs_ops.to_can_use_hw_breakpoint = procfs_can_use_hw_breakpoint;
   procfs_ops.to_magic               = OPS_MAGIC;
@@ -5737,6 +5739,47 @@ proc_untrace_sysexit_cmd (char *args, in
   proc_trace_syscalls (args, from_tty, PR_SYSEXIT, FLAG_RESET);
 }
 
+char *
+procfs_read_aux_vector (int *lenp)
+{
+  char pathname[MAX_PROC_NAME_SIZE];
+  int fd;
+  char *buf, *p;
+  int bufsz, n;
+
+  sprintf (pathname, "/proc/%d/auxv", PIDGET (inferior_ptid));
+  fd = open_with_retry (pathname, O_RDONLY);
+  if (fd < 0)
+    return NULL;		/* XXX Call error here? */
+
+  bufsz = 256;
+  buf = (char *) xmalloc (bufsz);
+  p = buf;
+  while (1)
+    {
+      n = read (fd, p, buf + bufsz - p);
+      if (n == 0)		/* Hit EOF.  */
+	{
+	  *lenp = p - bufsz;
+	  break;
+	}
+      if (n < 0)		/* Read error.  */
+	{
+	  xfree (buf);
+	  buf = NULL;
+	  break;
+	}
+      bufsz *= 2;
+      n = p + n - buf;
+      buf = (char *) xrealloc (buf, bufsz);
+      p = buf + n;
+    }
+
+  close (fd);
+  return buf;
+}
+
+
 
 void
 _initialize_procfs (void)
@@ -5851,6 +5894,8 @@ procfs_make_note_section (bfd *obfd, int
   char *note_data = NULL;
   char *inf_args;
   struct procfs_corefile_thread_data thread_args;
+  char *auxv;
+  int auxv_len;
 
   if (get_exec_file (0))
     {
@@ -5897,6 +5942,14 @@ procfs_make_note_section (bfd *obfd, int
   else
     {
       note_data = thread_args.note_data;
+    }
+
+  auxv = target_read_aux_vector (&auxv_len);
+  if (auxv != NULL)
+    {
+      note_data = elfcore_write_note (obfd, note_data, note_size,
+				      "CORE", NT_AUXV, auxv, auxv_len);
+      xfree (auxv);
     }
 
   make_cleanup (xfree, note_data);
Index: corelow.c
===================================================================
RCS file: /cvs/src/src/gdb/corelow.c,v
retrieving revision 1.30
diff -b -p -u -r1.30 corelow.c
--- corelow.c	21 Sep 2003 01:26:44 -0000	1.30
+++ corelow.c	7 Oct 2003 01:20:31 -0000
@@ -474,6 +548,30 @@ core_files_info (struct target_ops *t)
   print_section_info (t, core_bfd);
 }
 
+static char *
+core_read_aux_vector (int *lenp)
+{
+  sec_ptr section;
+  bfd_size_type size;
+  char *contents;
+
+  section = bfd_get_section_by_name (core_bfd, ".auxv");
+  if (section == NULL)
+    return NULL;
+
+  size = bfd_section_size (core_bfd, section);
+  contents = (char *) xmalloc (size);
+  if (! bfd_get_section_contents (core_bfd, section, contents,
+				  (file_ptr) 0, size))
+    {
+      xfree (contents);
+      warning ("Couldn't read NT_AUXV note in core file.");
+      return NULL;
+    }
+
+  return contents;
+}
+
 /* If mourn is being called in all the right places, this could be say
    `gdb internal error' (since generic_mourn calls breakpoint_init_inferior).  */
 
@@ -520,6 +618,7 @@ init_core_ops (void)
   core_ops.to_has_memory = 1;
   core_ops.to_has_stack = 1;
   core_ops.to_has_registers = 1;
+  core_ops.to_read_aux_vector = core_read_aux_vector;
   core_ops.to_magic = OPS_MAGIC;
 }
 
Index: sol-thread.c
===================================================================
RCS file: /cvs/src/src/gdb/sol-thread.c,v
retrieving revision 1.38
diff -b -p -u -r1.38 sol-thread.c
--- sol-thread.c	21 Sep 2003 01:26:45 -0000	1.38
+++ sol-thread.c	7 Oct 2003 01:28:38 -0000
@@ -1522,6 +1522,12 @@ sol_find_memory_regions (int (*func) (CO
 }
 
 static char *
+sol_read_aux_vector (int *auxv_size)
+{
+  return procfs_ops.to_read_aux_vector (auxv_size);
+}
+
+static char *
 sol_make_note_section (bfd *obfd, int *note_size)
 {
   return procfs_ops.to_make_corefile_notes (obfd, note_size);
@@ -1575,6 +1581,7 @@ init_sol_thread_ops (void)
   sol_thread_ops.to_has_execution = 1;
   sol_thread_ops.to_has_thread_control = tc_none;
   sol_thread_ops.to_find_memory_regions = sol_find_memory_regions;
+  sol_thread_ops.to_read_aux_vector = sol_read_aux_vector;
   sol_thread_ops.to_make_corefile_notes = sol_make_note_section;
   sol_thread_ops.to_magic = OPS_MAGIC;
 }