[Bug breakpoints/14446] New: breakpoints may not work on jitted code

[Bug breakpoints/14446] New: breakpoints may not work on jitted code

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14446

             Bug #: 14446
           Summary: breakpoints may not work on jitted code
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
        AssignedTo: unassigned@sourceware.org
        ReportedBy: hjl.tools@gmail.com
    Classification: Unclassified


What happens are

1. V8 initializes memory for code with 0xdeadbeef.
2. When you set breakpoint in GDB, gdb saves and replaces one byte,
which happens to be 0xef in 0xdeadbeef, with 0xcc.
3. V8 writes out real instructions in memory.
4. When breakpoint is hit, GDB replaces 0xcc with 0xef.
5. V8 crashes due to 0xef.

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[Bug breakpoints/14446] breakpoints may not work on jitted code

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14446

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at redhat dot com

--- Comment #1 from Tom Tromey <tromey at redhat dot com> 2012-09-17 19:14:46 UTC ---
Could you elaborate on when gdb can put a breakpoint into
uninitialized memory?

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[Bug breakpoints/14446] breakpoints may not work on jitted code

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14446

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-17 19:40:01 UTC ---
(In reply to comment #1)
> Could you elaborate on when gdb can put a breakpoint into
> uninitialized memory?

We can set a watchpoint on the breakpoint and catch the
new value.  GDB restores the new value instead of the
old saved value.

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