[RFC] Limit attempts to place breakpoints on _start, __start, and main in solib-svr4.c

[Kevin Buettner <kevinb at redhat dot com>]

About a month and a half ago, I posted a patch which prevented
enable_break() in solib-svr4.c from placing breakpoints on _start,
__start, or main.  See:

http://www.sourceware.org/ml/gdb-patches/2010-09/msg00309.html

Mark Kettenis objected to that patch on the grounds that placing
breakpoints on _start, __start, or main can still be useful.  He
agreed, however, that it would be acceptable to skip attempts to
place these breakpoints when attaching to a process.  

The patch below preserves the current behavior when a program is
started via GDB's "run" command, but disables attempts to place
breakpoints on _start, __start, and main for all other cases (attach,
follow-fork, core file case, etc.)

Comments?

	* infcmd.c (post_create_inferior):  Add new parameter,
	`from_run_command'.  Pass this argument to
	`solib_create_inferior_hook'.
	(run_command_1): Pass 1 as value for the `from_run_command'
	argument in call to post_create_inferior().
	(attach_command_post_wait): Pass 0 as value for the
	`from_run_command' argument in call to post_create_inferior().
	* inferior.h (post_create_inferior): Update declaration to
	have an additional argument.
	* corelow.c (core_open): Pass 0 as the value of the
	`from_run_command' argument in call to post_create_inferior().
	* infrun.c (start_remote): Likewise.
	* tracepoint.c (tfile_open): Likewise.
	* solib.c, solib.h (solib_create_inferior_hook): Add new
	parameter, `from_run_command'.
	* solist.c (struct target_so_ops): Add new parameter,
	`from_run_command', to the `solib_create_inferior_hook' operation.
	* solib.c (reload_shared_libraries): Pass 0 as value of the
	`from_run_command' argument in call to solib_create_inferior_hook().
	* infrun.c (follow_exec): Likewise.
	* linux-nat.c (linux_child_follow_fork): Likewise.
	* nto-procfs.c (procfs_post_attach, procfs_create_inferior):
	Likewise.
	* solib-darwin.c (darwin_solib_create_inferior_hook): Add
	new parameter, `from_run_command'.
	* solib-frv.c (frv_solib_create_inferior_hook): Likewise.
	* solib-irix.c (irix_solib_create_inferior_hook): Likewise.
	* solib-osf.c (osf_solib_create_inferior_hook): Likewise.
	* solib-pa64.c (pa64_solib_create_inferior_hook): Likewise.
	* solib-som.c (som_solib_create_inferior_hook): Likewise.
	* solib-spu.c (spu_solib_create_inferior_hook): Likewise.
	* solib-sunos.c (sunos_solib_create_inferior_hook): Likewise.
	* solib-target.c (solib_target_solib_create_inferior_hook):
	Likewise.
	* solib-svr4.c (svr4_solib_create_inferior_hook): Likewise.
	Pass `from_run_command' to enable_break().
	(enable_break): Add new parameter, `from_run_command'.  Don't
	attempt to place a breakpoint on the bkpt_names[] symbols
	unless `from_run_command' is non-zero.

Index: corelow.c
===================================================================
RCS file: /cvs/src/src/gdb/corelow.c,v
retrieving revision 1.104
diff -u -p -r1.104 corelow.c
--- corelow.c	6 Sep 2010 13:59:02 -0000	1.104
+++ corelow.c	29 Nov 2010 20:54:29 -0000
@@ -415,7 +415,7 @@ core_open (char *filename, int from_tty)
 	switch_to_thread (thread->ptid);
     }
 
-  post_create_inferior (&core_ops, from_tty);
+  post_create_inferior (&core_ops, from_tty, 0);
 
   /* Now go through the target stack looking for threads since there
      may be a thread_stratum target loaded on top of target core by
Index: infcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/infcmd.c,v
retrieving revision 1.269
diff -u -p -r1.269 infcmd.c
--- infcmd.c	1 Jul 2010 15:36:15 -0000	1.269
+++ infcmd.c	29 Nov 2010 20:54:30 -0000
@@ -390,7 +390,8 @@ strip_bg_char (char **args)
    should be stopped.  */
 
 void
-post_create_inferior (struct target_ops *target, int from_tty)
+post_create_inferior (struct target_ops *target, int from_tty,
+                      int from_run_command)
 {
   /* Be sure we own the terminal in case write operations are performed.  */ 
   target_terminal_ours ();
@@ -411,7 +412,7 @@ post_create_inferior (struct target_ops 
 #ifdef SOLIB_CREATE_INFERIOR_HOOK
       SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
 #else
-      solib_create_inferior_hook (from_tty);
+      solib_create_inferior_hook (from_tty, from_run_command);
 #endif
     }
 
@@ -579,7 +580,7 @@ run_command_1 (char *args, int from_tty,
 
   /* Pass zero for FROM_TTY, because at this point the "run" command
      has done its thing; now we are setting up the running program.  */
-  post_create_inferior (&current_target, 0);
+  post_create_inferior (&current_target, 0, 1);
 
   /* Start the target running.  Do not use -1 continuation as it would skip
      breakpoint right at the entry point.  */
@@ -2290,7 +2291,7 @@ attach_command_post_wait (char *args, in
   /* Take any necessary post-attaching actions for this platform.  */
   target_post_attach (PIDGET (inferior_ptid));
 
-  post_create_inferior (&current_target, from_tty);
+  post_create_inferior (&current_target, from_tty, 0);
 
   /* Install inferior's terminal modes.  */
   target_terminal_inferior ();
Index: inferior.h
===================================================================
RCS file: /cvs/src/src/gdb/inferior.h,v
retrieving revision 1.145
diff -u -p -r1.145 inferior.h
--- inferior.h	24 Jun 2010 15:17:30 -0000	1.145
+++ inferior.h	29 Nov 2010 20:54:30 -0000
@@ -267,7 +267,7 @@ void set_step_info (struct frame_info *f
 
 /* From infcmd.c */
 
-extern void post_create_inferior (struct target_ops *, int);
+extern void post_create_inferior (struct target_ops *, int, int);
 
 extern void attach_command (char *, int);
 
Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.457
diff -u -p -r1.457 infrun.c
--- infrun.c	24 Nov 2010 19:08:30 -0000	1.457
+++ infrun.c	29 Nov 2010 20:54:30 -0000
@@ -848,7 +848,7 @@ follow_exec (ptid_t pid, char *execd_pat
 #ifdef SOLIB_CREATE_INFERIOR_HOOK
   SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
 #else
-  solib_create_inferior_hook (0);
+  solib_create_inferior_hook (0, 0);
 #endif
 
   jit_inferior_created_hook ();
@@ -2141,7 +2141,7 @@ start_remote (int from_tty)
   /* Now that the inferior has stopped, do any bookkeeping like
      loading shared libraries.  We want to do this before normal_stop,
      so that the displayed frame is up to date.  */
-  post_create_inferior (&current_target, from_tty);
+  post_create_inferior (&current_target, from_tty, 0);
 
   normal_stop ();
 }
Index: linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-nat.c,v
retrieving revision 1.186
diff -u -p -r1.186 linux-nat.c
--- linux-nat.c	2 Nov 2010 01:37:32 -0000	1.186
+++ linux-nat.c	29 Nov 2010 20:54:30 -0000
@@ -767,7 +767,7 @@ holding the child stopped.  Try \"set de
 		 breakpoint.  If a "cloned-VM" event was propagated
 		 better throughout the core, this wouldn't be
 		 required.  */
-	      solib_create_inferior_hook (0);
+	      solib_create_inferior_hook (0, 0);
 	    }
 
 	  /* Let the thread_db layer learn about this new process.  */
@@ -949,7 +949,7 @@ Attaching after process %d fork to child
 	     shared libraries, and install the solib event breakpoint.
 	     If a "cloned-VM" event was propagated better throughout
 	     the core, this wouldn't be required.  */
-	  solib_create_inferior_hook (0);
+	  solib_create_inferior_hook (0, 0);
 	}
 
       /* Let the thread_db layer learn about this new process.  */
Index: nto-procfs.c
===================================================================
RCS file: /cvs/src/src/gdb/nto-procfs.c,v
retrieving revision 1.54
diff -u -p -r1.54 nto-procfs.c
--- nto-procfs.c	7 Jul 2010 16:15:16 -0000	1.54
+++ nto-procfs.c	29 Nov 2010 20:54:30 -0000
@@ -651,7 +651,7 @@ static void
 procfs_post_attach (pid_t pid)
 {
   if (exec_bfd)
-    solib_create_inferior_hook (0);
+    solib_create_inferior_hook (0, 0);
 }
 
 static ptid_t
@@ -1212,7 +1212,7 @@ procfs_create_inferior (struct target_op
 
   if (exec_bfd != NULL
       || (symfile_objfile != NULL && symfile_objfile->obfd != NULL))
-    solib_create_inferior_hook (0);
+    solib_create_inferior_hook (0, 0);
 }
 
 static void
Index: solib-darwin.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-darwin.c,v
retrieving revision 1.14
diff -u -p -r1.14 solib-darwin.c
--- solib-darwin.c	16 May 2010 23:49:58 -0000	1.14
+++ solib-darwin.c	29 Nov 2010 20:54:30 -0000
@@ -296,7 +296,7 @@ darwin_special_symbol_handling (void)
 /* Shared library startup support.  See documentation in solib-svr4.c  */
 
 static void
-darwin_solib_create_inferior_hook (int from_tty)
+darwin_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct minimal_symbol *msymbol;
   char **bkpt_namep;
Index: solib-frv.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-frv.c,v
retrieving revision 1.35
diff -u -p -r1.35 solib-frv.c
--- solib-frv.c	16 May 2010 23:49:58 -0000	1.35
+++ solib-frv.c	29 Nov 2010 20:54:30 -0000
@@ -979,7 +979,7 @@ frv_relocate_main_executable (void)
 
    SYNOPSIS
 
-   void frv_solib_create_inferior_hook ()
+   void frv_solib_create_inferior_hook (int from_tty, int from_run_commnad)
 
    DESCRIPTION
 
@@ -994,7 +994,7 @@ frv_relocate_main_executable (void)
  */
 
 static void
-frv_solib_create_inferior_hook (int from_tty)
+frv_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   /* Relocate main executable.  */
   frv_relocate_main_executable ();
Index: solib-irix.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-irix.c,v
retrieving revision 1.35
diff -u -p -r1.35 solib-irix.c
--- solib-irix.c	16 May 2010 23:49:58 -0000	1.35
+++ solib-irix.c	29 Nov 2010 20:54:30 -0000
@@ -392,7 +392,7 @@ enable_break (void)
 
    SYNOPSIS
 
-   void solib_create_inferior_hook (int from_tty)
+   void solib_create_inferior_hook (int from_tty, int from_run_command)
 
    DESCRIPTION
 
@@ -437,7 +437,7 @@ enable_break (void)
  */
 
 static void
-irix_solib_create_inferior_hook (int from_tty)
+irix_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct inferior *inf;
   struct thread_info *tp;
Index: solib-osf.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-osf.c,v
retrieving revision 1.30
diff -u -p -r1.30 solib-osf.c
--- solib-osf.c	16 May 2010 23:49:58 -0000	1.30
+++ solib-osf.c	29 Nov 2010 20:54:30 -0000
@@ -307,7 +307,7 @@ osf_clear_solib (void)
    Also, what if child has exit()ed?  Must exit loop somehow.  */
 
 static void
-osf_solib_create_inferior_hook (int from_tty)
+osf_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct inferior *inf;
   struct thread_info *tp;
Index: solib-pa64.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-pa64.c,v
retrieving revision 1.25
diff -u -p -r1.25 solib-pa64.c
--- solib-pa64.c	16 May 2010 23:49:58 -0000	1.25
+++ solib-pa64.c	29 Nov 2010 20:54:30 -0000
@@ -329,7 +329,7 @@ bfd_lookup_symbol (bfd *abfd, char *symn
    with shared libraries mapped shareable.  */
 
 static void
-pa64_solib_create_inferior_hook (int from_tty)
+pa64_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct minimal_symbol *msymbol;
   unsigned int dld_flags, status;
Index: solib-som.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-som.c,v
retrieving revision 1.30
diff -u -p -r1.30 solib-som.c
--- solib-som.c	17 Oct 2010 17:45:16 -0000	1.30
+++ solib-som.c	29 Nov 2010 20:54:30 -0000
@@ -183,7 +183,7 @@ struct {
    means running until the "_start" is called.  */
 
 static void
-som_solib_create_inferior_hook (int from_tty)
+som_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
   struct minimal_symbol *msymbol;
Index: solib-spu.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-spu.c,v
retrieving revision 1.12
diff -u -p -r1.12 solib-spu.c
--- solib-spu.c	25 Jun 2010 22:00:59 -0000	1.12
+++ solib-spu.c	29 Nov 2010 20:54:30 -0000
@@ -464,7 +464,7 @@ ocl_enable_break (struct objfile *objfil
 
 /* Create inferior hook.  */
 static void
-spu_solib_create_inferior_hook (int from_tty)
+spu_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   /* Handle SPE stand-alone executables.  */
   if (spu_standalone_p ())
@@ -491,7 +491,7 @@ spu_solib_create_inferior_hook (int from
     }
 
   /* Call SVR4 hook -- this will re-insert the SVR4 solib breakpoints.  */
-  svr4_so_ops.solib_create_inferior_hook (from_tty);
+  svr4_so_ops.solib_create_inferior_hook (from_tty, from_run_command);
 
   /* If the inferior is statically linked against libspe, we need to install
      our own solib breakpoint right now.  Otherwise, it will be installed by
Index: solib-sunos.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-sunos.c,v
retrieving revision 1.39
diff -u -p -r1.39 solib-sunos.c
--- solib-sunos.c	8 Jan 2010 22:52:03 -0000	1.39
+++ solib-sunos.c	29 Nov 2010 20:54:30 -0000
@@ -741,7 +741,7 @@ sunos_special_symbol_handling (void)
  */
 
 static void
-sunos_solib_create_inferior_hook (int from_tty)
+sunos_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct thread_info *tp;
   struct inferior *inf;
Index: solib-svr4.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-svr4.c,v
retrieving revision 1.139
diff -u -p -r1.139 solib-svr4.c
--- solib-svr4.c	11 Oct 2010 08:50:33 -0000	1.139
+++ solib-svr4.c	29 Nov 2010 20:54:30 -0000
@@ -1342,7 +1342,7 @@ exec_entry_point (struct bfd *abfd, stru
  */
 
 static int
-enable_break (struct svr4_info *info, int from_tty)
+enable_break (struct svr4_info *info, int from_tty, int from_run_command)
 {
   struct minimal_symbol *msymbol;
   const char * const *bkpt_namep;
@@ -1607,17 +1607,24 @@ enable_break (struct svr4_info *info, in
 	}
     }
 
-  for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
+  /* If all of the above have failed, and we're running the program from
+     scratch, try placing a breakpoint on one of the names in the bkpt_names[]
+     list.  */
+
+  if (from_run_command)
     {
-      msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
-      if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
+      for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
 	{
-	  sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
-	  sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
-							 sym_addr,
-							 &current_target);
-	  create_solib_event_breakpoint (target_gdbarch, sym_addr);
-	  return 1;
+	  msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
+	  if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
+	    {
+	      sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
+	      sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
+							     sym_addr,
+							     &current_target);
+	      create_solib_event_breakpoint (target_gdbarch, sym_addr);
+	      return 1;
+	    }
 	}
     }
   return 0;
@@ -2110,7 +2117,7 @@ svr4_relocate_main_executable (void)
 
    SYNOPSIS
 
-   void svr4_solib_create_inferior_hook (int from_tty)
+   void svr4_solib_create_inferior_hook (int from_tty, int from_run_command)
 
    DESCRIPTION
 
@@ -2155,7 +2162,7 @@ svr4_relocate_main_executable (void)
  */
 
 static void
-svr4_solib_create_inferior_hook (int from_tty)
+svr4_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
 #if defined(_SCO_DS)
   struct inferior *inf;
@@ -2171,7 +2178,7 @@ svr4_solib_create_inferior_hook (int fro
   if (!svr4_have_link_map_offsets ())
     return;
 
-  if (!enable_break (info, from_tty))
+  if (!enable_break (info, from_tty, from_run_command))
     return;
 
 #if defined(_SCO_DS)
Index: solib-target.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-target.c,v
retrieving revision 1.16
diff -u -p -r1.16 solib-target.c
--- solib-target.c	15 Jun 2010 17:57:38 -0000	1.16
+++ solib-target.c	29 Nov 2010 20:54:30 -0000
@@ -307,7 +307,7 @@ solib_target_special_symbol_handling (vo
 }
 
 static void
-solib_target_solib_create_inferior_hook (int from_tty)
+solib_target_solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   /* Nothing needed.  */
 }
Index: solib.c
===================================================================
RCS file: /cvs/src/src/gdb/solib.c,v
retrieving revision 1.141
diff -u -p -r1.141 solib.c
--- solib.c	5 Nov 2010 01:40:28 -0000	1.141
+++ solib.c	29 Nov 2010 20:54:30 -0000
@@ -1217,21 +1217,22 @@ clear_solib (void)
 
    SYNOPSIS
 
-   void solib_create_inferior_hook (int from_tty)
+   void solib_create_inferior_hook (int from_tty, int from_run_command)
 
    DESCRIPTION
 
    When gdb starts up the inferior, it nurses it along (through the
-   shell) until it is ready to execute it's first instruction.  At this
-   point, this function gets called via expansion of the macro
-   SOLIB_CREATE_INFERIOR_HOOK.  */
+   shell) until it is ready to execute it's first instruction.
+   
+   The flag FROM_RUN_COMMAND will be 1 if this function is invoked due
+   to the running of a new program; otherwise it is 0.  */
 
 void
-solib_create_inferior_hook (int from_tty)
+solib_create_inferior_hook (int from_tty, int from_run_command)
 {
   struct target_so_ops *ops = solib_ops (target_gdbarch);
 
-  ops->solib_create_inferior_hook (from_tty);
+  ops->solib_create_inferior_hook (from_tty, from_run_command);
 }
 
 /* GLOBAL FUNCTION
@@ -1396,7 +1397,7 @@ reload_shared_libraries (char *ignored, 
 #ifdef SOLIB_CREATE_INFERIOR_HOOK
       SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
 #else
-      solib_create_inferior_hook (from_tty);
+      solib_create_inferior_hook (from_tty, 0);
 #endif
     }
 
Index: solib.h
===================================================================
RCS file: /cvs/src/src/gdb/solib.h,v
retrieving revision 1.28
diff -u -p -r1.28 solib.h
--- solib.h	8 Jan 2010 22:52:04 -0000	1.28
+++ solib.h	29 Nov 2010 20:54:30 -0000
@@ -42,7 +42,7 @@ extern int solib_read_symbols (struct so
    addresses to which they are linked, and sufficient information to
    read in their symbols at a later time.  */
 
-extern void solib_create_inferior_hook (int from_tty);
+extern void solib_create_inferior_hook (int from_tty, int from_run_command);
 
 /* If ADDR lies in a shared library, return its name.  */
 
Index: solist.h
===================================================================
RCS file: /cvs/src/src/gdb/solist.h,v
retrieving revision 1.32
diff -u -p -r1.32 solist.h
--- solist.h	22 Apr 2010 23:15:41 -0000	1.32
+++ solist.h	29 Nov 2010 20:54:30 -0000
@@ -94,7 +94,7 @@ struct target_so_ops
     void (*clear_solib) (void);
 
     /* Target dependent code to run after child process fork.  */
-    void (*solib_create_inferior_hook) (int from_tty);
+    void (*solib_create_inferior_hook) (int from_tty, int from_run_command);
 
     /* Do additional symbol handling, lookup, etc. after symbols
        for a shared object have been loaded.  */
Index: tracepoint.c
===================================================================
RCS file: /cvs/src/src/gdb/tracepoint.c,v
retrieving revision 1.197
diff -u -p -r1.197 tracepoint.c
--- tracepoint.c	1 Nov 2010 07:00:13 -0000	1.197
+++ tracepoint.c	29 Nov 2010 20:54:31 -0000
@@ -3312,7 +3312,7 @@ tfile_open (char *filename, int from_tty
   inferior_ptid = pid_to_ptid (TFILE_PID);
   add_thread_silent (inferior_ptid);
 
-  post_create_inferior (&tfile_ops, from_tty);
+  post_create_inferior (&tfile_ops, from_tty, 0);
 
 #if 0
   /* FIXME this will get defined in MI patch submission */