On Tue, Oct 15, 2013 at 02:00:50PM -0400, Pavel Roskin wrote:
> Hi Chris,
>
> It's almost certainly stack corruption. This "patch" fixes X for me.
> The first DRM_IOCTL_MODE_GETCONNECTOR in sna_output_init() must be
> overwriting the implied memory bounds.
>
> diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
> index 28151ab..dac834f 100644
> --- a/src/sna/sna_display.c
> +++ b/src/sna/sna_display.c
> @@ -2588,6 +2588,7 @@ sna_output_init(ScrnInfoPtr scrn, struct sna_mode *mode, int num)
> struct sna *sna = to_sna(scrn);
> xf86OutputPtr output;
> struct drm_mode_get_connector conn;
> + int enc_protect[16];
Yikes, that implies we have a size mismatch with the kernel - ideally we
construct the struct to have the same size when compiled with 32 or 64 bits.
Please try:
commit a63b4d5a0766a7e98efeff8dd520c58e9a1bea88
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Tue Oct 15 21:53:16 2013 +0100
sna: Expand packed KMS structs for 64-bit alignment
Pavel Roskin found that with a 32-bit build of the DDX with a 64-bit
kernel that the call to GETCONNECTOR was overwriting the 4 bytes beyond
the end of the drm_mode_get_connector structure. This would appear to be
due to the surreptious padding inserted by the compiler so that the
structure would be naturally aligned on a 64-bit system. To compenstate
we need to insert padding between the adjacent 32-bit structures on the
stack.
As usual, be paranoid and make sure that all the adjacent KMS structs we
use are padded out to an 64-bit boundary.
Reported-by: Pavel Roskin <proski@xxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Thanks,
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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