• Jeff Dike's avatar
    uml: kill processes instead of panicing kernel · 3e6f2ac4
    Jeff Dike authored
    UML was panicing in the case of failures of libc calls which shouldn't happen.
     This is an overreaction since a failure from libc doesn't normally mean that
    kernel data structures are in an unknown state.  Instead, the current process
    should just be killed if there is no way to recover.
    
    The case that prompted this was a failure of PTRACE_SETREGS restoring the same
    state that was read by PTRACE_GETREGS.  It appears that when a process tries
    to load a bogus value into a segment register, it segfaults (as expected) and
    the value is actually loaded and is seen by PTRACE_GETREGS (not expected).
    
    This case is fixed by forcing a fatal SIGSEGV on the process so that it
    immediately dies.  fatal_sigsegv was added for this purpose.  It was declared
    as noreturn, so in order to pursuade gcc that it actually does not return, I
    added a call to os_dump_core (and declared it noreturn) so that I get a core
    file if somehow the process survives.
    
    All other calls in arch/um/os-Linux/skas/process.c got the same treatment,
    with failures causing the process to die instead of a kernel panic, with some
    exceptions.
    
    userspace_tramp exits with status 1 if anything goes wrong there.  That will
    cause start_userspace to return an error.  copy_context_skas0 and
    map_stub_pages also now return errors instead of panicing.  Callers of thes
    functions were changed to check for errors and do something appropriate.
    Usually that's to return an error to their callers.
    check_skas3_ptrace_faultinfo just exits since that's too early to do anything
    else.
    
    save_registers, restore_registers, and init_registers now return status
    instead of panicing on failure, with their callers doing something
    appropriate.
    
    There were also duplicate declarations of save_registers and restore_registers
    in os.h - these are gone.
    
    I noticed and fixed up some whitespace damage.
    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>
    3e6f2ac4
trap.c 6.1 KB