Bug 65357

From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0; T312461)

Description of problem:
If you are debugging a program and modify read only pages (by setting
a breakpoint, for example), then the modified pages are now writable
by the user process being debugged as well.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Compile attached bug.c program (with -g)
2. Run it and watch it segfault
3. Now run gdb on the program.
4. Set a breakpoint at *&main
5. Let the program run to the breakpoint, then continue it.
6. Watch the program run with no errors and overwrite &main.	

Actual Results:  Program does not segfault.

Expected Results:  Program should segfault. Just because it is running under
the debugger, read/execute pages should not become writable.

By the way: The /proc address map info still shows the page
as read/execute even though it really is writable after you
set the breakpoint.


Additional info:

Here is the bug.c source code (its small):

  #include <stdio.h>

  int
  main(int argc, char ** argv) {
     int * mainprog = ((int *)(void *)&main);
     printf("Main program starts at %#x\n", mainprog);
     printf("First word looks like 0x%08x\n", *mainprog);
     printf("About to try writing on it...\n");
     fflush(stdout);
     *mainprog = 0xdeadbeef;
     printf("First word now looks like 0x%08x\n", *mainprog);
     fflush(stdout);
     return 0;
  }