[Bug breakpoints/11094] New: cannot reexecute programs using the GDB JIT interface in shared libs

["edwintorok at gmail dot com" <sourceware-bugzilla@sourceware.org>]

When trying to debug a program (for example ClamAV) that uses the GDB JIT inside
a shared lib (for example LLVM in libclamavc++.so), then I cannot reexecute the
program.
This happens when no code was registered with the JIT interface, such as when I
simply put a breakpoint on main, and try to run twice, the 2nd run will fail
telling me it couldn't reset breakpoint -4 (or -2).

I've created a small testcase to show this problem (will attach), here is the
output:
--- shared.c:                                                                
#include <stdint.h>                                                          
typedef enum                                                                 
{                                                                            
  JIT_NOACTION = 0,                                                          
  JIT_REGISTER_FN,                                                           
  JIT_UNREGISTER_FN                                                          
} jit_actions_t;                                                             

struct jit_code_entry
{                    
  struct jit_code_entry *next_entry;
  struct jit_code_entry *prev_entry;
  const char *symfile_addr;         
  uint64_t symfile_size;            
};                                  

struct jit_descriptor
{                    
  uint32_t version;  
  /* This type should be jit_actions_t, but we use uint32_t
     to be explicit about the bitwidth.  */                
  uint32_t action_flag;                                    
  struct jit_code_entry *relevant_entry;                   
  struct jit_code_entry *first_entry;                      
};                                                         

/* GDB puts a breakpoint in this function.  */
void __attribute__((noinline)) __jit_debug_register_code() { };

/* Make sure to specify the version statically, because the
   debugger may check the version before we can set it.  */
struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
int foo() {                                                   
    return 4;                                                 
}                                                             

--- bp_minus4.c:
int foo();      
int main()      
{               
    return foo();
}                

gcc (Debian 4.4.2-5) 4.4.2
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

GNU gdb (GDB) 7.0-debian
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/edwin/gdbbug/bp_minus4...done.
Breakpoint 1 at 0x4005f8: file bp_minus4.c, line 4.

Breakpoint 1, main () at bp_minus4.c:4
4           return foo();
/home/edwin/gdbbug/gdb.tmp:3: Error in sourced command file:
Warning:
Cannot insert breakpoint -2.
Error accessing memory address 0x7ffff7dfa5dc: Input/output error.

(gdb) maint info breakpoints
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000004005f8 in main at bp_minus4.c:4
-2      jit events     keep y   0x00007ffff7dfa5dc
-9      shlib events   keep y   0x000000381da0dcc0 <*__GI__dl_debug_state>
(gdb) quit
A debugging session is active.

        Inferior 2 [process 18147] will be killed.

Quit anyway? (y or n) y

-- 
           Summary: cannot reexecute programs using the GDB JIT interface in
                    shared libs
           Product: gdb
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: breakpoints
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: edwintorok at gmail dot com
                CC: gdb-prs at sourceware dot org
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=11094

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