On Wed, Mar 24, 2021 at 05:30:24PM +0200, Jani Nikula wrote:
On Mon, 22 Mar 2021, Arnd Bergmann arnd@kernel.org wrote:
From: Arnd Bergmann arnd@arndb.de
gcc-11 warns about what appears to be an out-of-range array access:
In function ‘snb_wm_latency_quirk’, inlined from ‘ilk_setup_wm_latency’ at drivers/gpu/drm/i915/intel_pm.c:3108:3: drivers/gpu/drm/i915/intel_pm.c:3057:9: error: ‘intel_print_wm_latency’ reading 16 bytes from a region of size 10 [-Werror=stringop-overread] 3057 | intel_print_wm_latency(dev_priv, "Primary", dev_priv->wm.pri_latency); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i915/intel_pm.c: In function ‘ilk_setup_wm_latency’: drivers/gpu/drm/i915/intel_pm.c:3057:9: note: referencing argument 3 of type ‘const u16 *’ {aka ‘const short unsigned int *’} drivers/gpu/drm/i915/intel_pm.c:2994:13: note: in a call to function ‘intel_print_wm_latency’ 2994 | static void intel_print_wm_latency(struct drm_i915_private *dev_priv, | ^~~~~~~~~~~~~~~~~~~~~~
My guess is that this code is actually safe because the size of the array depends on the hardware generation, and the function checks for that, but at the same time I would not expect the compiler to work it out correctly, and the code seems a little fragile with regards to future changes. Simply increasing the size of the array should help.
Agreed, I don't think there's an issue, but the code could use a bunch of improvements.
Like, we have intel_print_wm_latency() for debug logging and wm_latency_show() for debugfs, and there's a bunch of duplication and ugh.
There is all this ancient stuff in review limbo... https://patchwork.freedesktop.org/series/50802/