From: Roland McGrath Date: Mon, 24 Sep 2007 23:52:44 +0000 (-0700) Subject: [POWERPC] Ensure FULL_REGS on exec X-Git-Tag: v2.6.23-rc9~40^2~1 X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=474f81967217f3bec2389ae913da72641f2c40e3 [POWERPC] Ensure FULL_REGS on exec 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. Signed-off-by: Roland McGrath Signed-off-by: Paul Mackerras --- diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index e477c9d0498b..8a1b001d0b11 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;