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[PATCH/RFC 02/02 v2] Refactor PRPSINFO handling on GDB

Sergio Durigan Junior sergiodj@redhat.com
Fri Jan 4 04:41:00 GMT 2013 
On Monday, December 31 2013, Jan Kratochvil wrote:

> On Sun, 30 Dec 2012 02:53:18 +0100, Sergio Durigan Junior wrote:

Thanks for the comments.  Here is the updated version of it, reflecting
also the changes proposed on the BFD part.

Thanks,

-- 
Sergio

2013-01-04  Sergio Durigan Junior  <sergiodj@redhat.com>
	    Denys Vlasenko  <dvlasenk@redhat.com>

	* linux-tdep.c: Include `cli/cli-utils.h' and `exceptions.h'.
	(linux_fill_prpsinfo): New function.
	(linux_make_corefile_notes): Refactor code to gather information for
	PRPSINFO, using linux_nat_fill_prpsinfo.
	* procfs.c (procfs_make_note_section): Refactor code to gather basic
	information for PRPSINFO.

---
 gdb/linux-tdep.c |  210 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 gdb/procfs.c     |   36 +++++-----
 2 files changed, 212 insertions(+), 34 deletions(-)

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 836da62..fb62207 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -32,6 +32,8 @@
 #include "cli/cli-utils.h"
 #include "arch-utils.h"
 #include "gdb_obstack.h"
+#include "cli/cli-utils.h"
+#include "exceptions.h"
 
 #include <ctype.h>
 
@@ -1153,6 +1155,193 @@ linux_corefile_thread_callback (struct thread_info *info, void *data)
   return !args->note_data;
 }
 
+/* Fill the PRPSINFO structure with information about the process being
+   debugged.  Returns 1 in case of success, 0 for failures.  Please note that
+   even if the structure cannot be entirely filled (e.g., GDB was unable to
+   gather information about the process UID/GID), this function will still
+   return 1 since some information was already recorded.  It will only return
+   0 iff nothing can be gathered.  */
+
+static int
+linux_fill_prpsinfo (struct elf_internal_prpsinfo *p)
+{
+  /* The filename which we will use to obtain some info about the process.
+     We will basically use this to store the `/proc/PID/FILENAME' file.  */
+  char filename[100];
+  /* The full name of the program which generated the corefile.  */
+  char *fname;
+  /* The basename of the executable.  */
+  const char *basename;
+  /* The arguments of the program.  */
+  char *psargs;
+  char *infargs;
+  /* The contents of `/proc/PID/stat' file.  */
+  char *proc_stat;
+  /* The valid states of a process, according to the Linux kernel.  */
+  const char valid_states[] = "RSDTZW";
+  /* The program state.  */
+  const char *prog_state;
+  /* The state of the process.  */
+  char pr_sname;
+  /* The PID of the program which generated the corefile.  */
+  pid_t pid;
+  /* Process flags.  */
+  unsigned int pr_flag;
+  /* Process nice value.  */
+  long pr_nice;
+  /* The stat of the `/proc/PID/stat' file.  */
+  struct stat proc_st;
+  /* The number of fields read by `sscanf'.  */
+  int n_fields = 0;
+  /* Cleanups.  */
+  struct cleanup *c;
+  int i;
+  volatile struct gdb_exception ex;
+
+  gdb_assert (p != NULL);
+
+  /* Obtaining PID and filename.  */
+  pid = ptid_get_pid (inferior_ptid);
+  xsnprintf (filename, sizeof (filename), "/proc/%u/cmdline", pid);
+  fname = target_fileio_read_stralloc (filename);
+
+  if (fname == NULL || *fname == '\0')
+    {
+      /* No program name was read, so we won't be able to retrieve more
+	 information about the process.  */
+      xfree (fname);
+      return 0;
+    }
+
+  c = make_cleanup (xfree, fname);
+  memset (p, 0, sizeof (*p));
+
+  /* Obtaining the file stat as well.  */
+  if (stat (filename, &proc_st) != 0)
+    {
+      warning (_("Could not stat file `%s': %s"), filename,
+	       safe_strerror (errno));
+      p->pr_uid = 0;
+      p->pr_gid = 0;
+    }
+  else
+    {
+      p->pr_uid = proc_st.st_uid;
+      p->pr_gid = proc_st.st_gid;
+    }
+
+  /* Defining the PID.  */
+  p->pr_pid = pid;
+
+  /* Copying the program name.  Only the basename matters.  */
+  basename = lbasename (fname);
+  strncpy (p->pr_fname, basename, sizeof (p->pr_fname));
+  p->pr_fname[sizeof (p->pr_fname) - 1] = '\0';
+
+  /* Generating and copying the program's arguments.  `get_inferior_args'
+     may throw, but we want to continue the execution anyway.  */
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      infargs = get_inferior_args ();
+    }
+
+  if (ex.reason < 0)
+    {
+      warning (_("Could not obtain inferior's arguments: %s"), ex.message);
+      infargs = NULL;
+    }
+
+  psargs = xstrdup (fname);
+  if (infargs != NULL)
+    psargs = reconcat (psargs, psargs, " ", infargs, NULL);
+
+  make_cleanup (xfree, psargs);
+
+  strncpy (p->pr_psargs, psargs, sizeof (p->pr_psargs));
+  p->pr_psargs[sizeof (p->pr_psargs) - 1] = '\0';
+
+  xsnprintf (filename, sizeof (filename), "/proc/%d/stat", (int) pid);
+  proc_stat = target_fileio_read_stralloc (filename);
+  make_cleanup (xfree, proc_stat);
+
+  if (proc_stat == NULL || *proc_stat == '\0')
+    {
+      /* Despite being unable to read more information about the process, we
+	 return 1 here because at least we have its command line, PID and
+	 arguments.  */
+      do_cleanups (c);
+      return 1;
+    }
+
+  /* Ok, we have the stats.  It's time to do a little parsing of the contents
+     of the buffer, so that we end up reading what we want.
+
+     The following parsing mechanism is strongly based on the information
+     generated by the `fs/proc/array.c' file, present in the Linux kernel
+     tree.  More details about how the information is displayed can be
+     obtained by seeing the manpage of proc(5), specifically under the entry
+     of `/proc/[pid]/stat'.  */
+
+  /* Getting rid of the PID, since we already have it.  */
+  while (isdigit (*proc_stat))
+    ++proc_stat;
+
+  proc_stat = skip_spaces (proc_stat);
+
+  /* Getting rid of the executable name, since we already have it.  We know
+     that this name will be in parentheses, so we can safely look for the
+     close-paren.  */
+  while (*proc_stat != ')')
+    ++proc_stat;
+  ++proc_stat;
+
+  proc_stat = skip_spaces (proc_stat);
+
+  n_fields = sscanf (proc_stat,
+		     "%c"		/* Process state.  */
+		     "%d%d%d"		/* Parent PID, group ID, session ID.  */
+		     "%*d%*d"		/* tty_nr, tpgid (not used).  */
+		     "%u"		/* Flags.  */
+		     "%*s%*s%*s%*s"	/* minflt, cminflt, majflt,
+					   cmajflt (not used).  */
+		     "%*s%*s%*s%*s"	/* utime, stime, cutime,
+					   cstime (not used).  */
+		     "%*s"		/* Priority (not used).  */
+		     "%ld",		/* Nice.  */
+		     &pr_sname,
+		     &p->pr_ppid, &p->pr_pgrp, &p->pr_sid,
+		     &pr_flag,
+		     &pr_nice);
+
+  if (n_fields != 6)
+    {
+      /* Again, we couldn't read the complementary information about the
+	 process state.  However, we already have minimal information, so we
+	 just return 1 here.  */
+      do_cleanups (c);
+      return 1;
+    }
+
+  /* Filling the structure fields.  */
+  prog_state = strchr (valid_states, pr_sname);
+  if (prog_state != NULL)
+    p->pr_state = prog_state - valid_states;
+  else
+    {
+      /* Zero means "Running".  */
+      p->pr_state = 0;
+    }
+
+  p->pr_sname = p->pr_state > 5 ? '.' : pr_sname;
+  p->pr_zomb = p->pr_sname == 'Z';
+  p->pr_nice = pr_nice;
+  p->pr_flag = pr_flag;
+
+  do_cleanups (c);
+
+  return 1;
+}
+
 /* Fills the "to_make_corefile_note" target vector.  Builds the note
    section for a corefile, and returns it in a malloc buffer.  */
 
@@ -1161,27 +1350,14 @@ linux_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size,
 			   linux_collect_thread_registers_ftype collect)
 {
   struct linux_corefile_thread_data thread_args;
+  struct elf_internal_prpsinfo prpsinfo;
   char *note_data = NULL;
   gdb_byte *auxv;
   int auxv_len;
 
-  /* Process information.  */
-  if (get_exec_file (0))
-    {
-      const char *fname = lbasename (get_exec_file (0));
-      char *psargs = xstrdup (fname);
-
-      if (get_inferior_args ())
-        psargs = reconcat (psargs, psargs, " ", get_inferior_args (),
-			   (char *) NULL);
-
-      note_data = elfcore_write_prpsinfo (obfd, note_data, note_size,
-                                          fname, psargs);
-      xfree (psargs);
-
-      if (!note_data)
-	return NULL;
-    }
+  if (linux_fill_prpsinfo (&prpsinfo))
+    note_data = elfcore_write_prpsinfo (obfd, note_data, note_size,
+					&prpsinfo);
 
   /* Thread register information.  */
   thread_args.gdbarch = gdbarch;
diff --git a/gdb/procfs.c b/gdb/procfs.c
index 20da81a..3921034 100644
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -5471,39 +5471,41 @@ procfs_make_note_section (bfd *obfd, int *note_size)
   struct cleanup *old_chain;
   gdb_gregset_t gregs;
   gdb_fpregset_t fpregs;
-  char fname[16] = {'\0'};
-  char psargs[80] = {'\0'};
+  struct elf_internal_prpsinfo prpsinfo;
   procinfo *pi = find_procinfo_or_die (PIDGET (inferior_ptid), 0);
   char *note_data = NULL;
-  char *inf_args;
   struct procfs_corefile_thread_data thread_args;
   gdb_byte *auxv;
   int auxv_len;
   enum gdb_signal stop_signal;
 
+  memset (&prpsinfo, 0, sizeof (prpsinfo));
+
   if (get_exec_file (0))
     {
-      strncpy (fname, lbasename (get_exec_file (0)), sizeof (fname));
-      fname[sizeof (fname) - 1] = 0;
-      strncpy (psargs, get_exec_file (0), sizeof (psargs));
-      psargs[sizeof (psargs) - 1] = 0;
+      char *inf_args;
+      char *psargs;
+
+      strncpy (prpsinfo.pr_fname, lbasename (get_exec_file (0)),
+	       sizeof (prpsinfo.pr_fname));
+      prpsinfo.pr_fname[sizeof (prpsinfo.pr_fname) - 1] = '\0';
+
+      psargs = xstrdup (prpsinfo.pr_fname);
 
       inf_args = get_inferior_args ();
-      if (inf_args && *inf_args &&
-	  strlen (inf_args) < ((int) sizeof (psargs) - (int) strlen (psargs)))
-	{
-	  strncat (psargs, " ",
-		   sizeof (psargs) - strlen (psargs));
-	  strncat (psargs, inf_args,
-		   sizeof (psargs) - strlen (psargs));
-	}
+      if (inf_args != NULL)
+	psargs = reconcat (psargs, psargs, " ", inf_args, NULL);
+
+      strncpy (prpsinfo.pr_psargs, psargs, sizeof (prpsinfo.pr_psargs));
+      prpsinfo.pr_psargs[sizeof (prpsinfo.pr_psargs) - 1] = '\0';
+
+      xfree (psargs);
     }
 
   note_data = (char *) elfcore_write_prpsinfo (obfd,
 					       note_data,
 					       note_size,
-					       fname,
-					       psargs);
+					       &prpsinfo);
 
   stop_signal = find_stop_signal ();
 
-- 
1.7.7.6
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