Re: [PATCH 4/6] Hexagon: check to if we will overflow the signal stack

[Richard Kuo]

On 04/04/2013 11:25 AM, Linas Vepstas wrote:

On 3 April 2013 19:02, Richard Kuo  wrote:


+   /* check if we would overflow the alt stack */
+   if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
+   return (void __user __force *)-1UL;

I found the !likely construction confusing, as its doing both a
'unlikely' (right?) and inverting the argument. It seems clearer,
to idiots like me, to write this as:

if (on_sig_stack(sp) && unlikely(!on_sig_stack(sp - frame_size)))

since where checking for overflow, and its unlikely that the overflow happened.

-- Linas


I'm not sure if putting a double negative in there will make it less not 
easy to understand...



--

Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 4/6] Hexagon: check to if we will overflow the signal stack

[Linas Vepstas]

On 3 April 2013 19:02, Richard Kuo  wrote:

> +   /* check if we would overflow the alt stack */
> +   if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
> +   return (void __user __force *)-1UL;

I found the !likely construction confusing, as its doing both a
'unlikely' (right?) and inverting the argument. It seems clearer,
to idiots like me, to write this as:

if (on_sig_stack(sp) && unlikely(!on_sig_stack(sp - frame_size)))

since where checking for overflow, and its unlikely that the overflow happened.

-- Linas
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[PATCH 4/6] Hexagon: check to if we will overflow the signal stack

[Richard Kuo]

Signed-off-by: Richard Kuo 
---
 arch/hexagon/kernel/signal.c |4 
 1 file changed, 4 insertions(+)

diff --git a/arch/hexagon/kernel/signal.c b/arch/hexagon/kernel/signal.c
index 8a20e8e..097623c 100644
--- a/arch/hexagon/kernel/signal.c
+++ b/arch/hexagon/kernel/signal.c
@@ -41,6 +41,10 @@ static void __user *get_sigframe(struct k_sigaction *ka, 
struct pt_regs *regs,
 {
unsigned long sp = regs->r29;
 
+   /* check if we would overflow the alt stack */
+   if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
+   return (void __user __force *)-1UL;
+
/* Switch to signal stack if appropriate */
if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
sp = current->sas_ss_sp + current->sas_ss_size;
-- 
1.7.9.5

--

Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/