From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Roland McGrath <roland@redhat.com>
Cc: David Woodhouse <dwmw2@redhat.com>,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
Paul Mackerras <paulus@samba.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 2/2] powerpc: FULL_REGS on exec
Date: Tue, 25 Sep 2007 10:34:20 +1000 [thread overview]
Message-ID: <1190680460.12382.11.camel@localhost.localdomain> (raw)
In-Reply-To: <20070924235244.2F3BB4D04B7@magilla.localdomain>
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 <roland@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> ---
> 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
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
prev parent reply other threads:[~2007-09-25 0:34 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-24 23:52 [PATCH 2/2] powerpc: FULL_REGS on exec Roland McGrath
2007-09-25 0:34 ` Benjamin Herrenschmidt [this message]
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