On Mon, 2007-09-24 at 16:52 -0700, Roland McGrath wrote: > When PTRACE_O_TRACEEXEC is used, a ptrace call to fetch the registers at > the PTRACE_EVENT_EXEC stop (PTRACE_PEEKUSR) will oops in CHECK_FULL_REGS. > With recent versions, "gdb --args /bin/sh -c 'exec /bin/true'" and "run" at > the (gdb) prompt is sufficient to produce this. I also have written an > isolated test case, see > https://bugzilla.redhat.com/show_bug.cgi?id=301791#c15. > > This change fixes the problem by clearing the low bit of pt_regs.trap in > start_thread so that FULL_REGS is true again. This is correct since all of > the GPRs that "full" refers to are cleared in start_thread.
Looks good, nice catch. > Signed-off-by: Roland McGrath <[EMAIL PROTECTED]> Signed-off-by: Benjamin Herrenschmidt <[EMAIL PROTECTED]> > --- > arch/powerpc/kernel/process.c | 7 +++++++ > 1 files changed, 7 insertions(+), 0 deletions(-) > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index e477c9d..fd799d2 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -605,6 +605,13 @@ void start_thread(struct pt_regs *regs, unsigned long > start, unsigned long sp) > regs->ccr = 0; > regs->gpr[1] = sp; > > + /* > + * We have just cleared all the nonvolatile GPRs, so make > + * FULL_REGS(regs) return true. This is necessary to allow > + * ptrace to examine the thread immediately after exec. > + */ > + regs->trap &= ~1UL; > + > #ifdef CONFIG_PPC32 > regs->mq = 0; > regs->nip = start; > _______________________________________________ > Linuxppc-dev mailing list > [EMAIL PROTECTED] > https://ozlabs.org/mailman/listinfo/linuxppc-dev - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
