• Stanislaw Gruszka's avatar
    uml: stop gdb from deleting breakpoints when running UML · 4dbed85a
    Stanislaw Gruszka authored
    Sometimes when UML is debugged gdb miss breakpoints.
    
    When process traced by gdb do fork, debugger remove breakpoints from
    child address space. There is possibility to trace more than one fork,
    but this not work with UML, I guess (only guess) there is a deadlock -
    gdb waits for UML and UML waits for gdb.
    
    When clone() is called with SIGCHLD and CLONE_VM flags, gdb see this
    as PTRACE_EVENT_FORK not as PTRACE_EVENT_CLONE and remove breakpoints
    from child and at the same time from traced process, because either
    have the same address space.
    
    Maybe it is possible to do fix in gdb, but I'm not sure if there is
    easy way to find out if traced and child processes share memory. So I
    do fix for UML, it simply do not call clone() with both SIGCHLD and
    CLONE_VM flags together.  Additionally __WALL flag is used for
    waitpid() to assure not miss clone and normal process events.
    
    [ jdike - checkpatch fixes ]
    Signed-off-by: default avatarStanislaw Gruszka <stf_xl@wp.pl>
    Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    4dbed85a
slip_user.c 5 KB