[RESEND v3 1/2] drm: enable (most) W=1 warnings by default across the subsystem

[Guenter Roeck]

Hi,

On Tue, Mar 05, 2024 at 11:07:35AM +0200, Jani Nikula wrote:
> At least the i915 and amd drivers enable a bunch more compiler warnings
> than the kernel defaults.
> 
> Extend most of the W=1 warnings to the entire drm subsystem by
> default. Use the copy-pasted warnings from scripts/Makefile.extrawarn
> with s/KBUILD_CFLAGS/subdir-ccflags-y/ to make it easier to compare and
> keep up with them in the future.
> 
> This is similar to the approach currently used in i915.
> 
> Some of the -Wextra warnings do need to be disabled, just like in
> Makefile.extrawarn, but take care to not disable them for W=2 or W=3
> builds, depending on the warning.
> 
> There are too many -Wformat-truncation warnings to cleanly fix up front;
> leave that warning disabled for now.
> 

With this patch in the mainline kernel, I get the following build error
when trying to build parisc:allmodconfig.

Error log:
drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_mthd':
drivers/gpu/drm/nouveau/nvif/object.c:161:9: error: 'memcpy' accessing 4294967264 or more bytes at offsets 0 and 32 overlaps 6442450881 bytes at offset -2147483617 [-Werror=restrict]
  161 |         memcpy(data, args->mthd.data, size);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/nouveau/nvif/object.c: In function 'nvif_object_ctor':
drivers/gpu/drm/nouveau/nvif/object.c:298:17: error: 'memcpy' accessing 4294967240 or more bytes at offsets 0 and 56 overlaps 6442450833 bytes at offset -2147483593 [-Werror=restrict]
  298 |                 memcpy(data, args->new.data, size);

The problem is also seen with v6.9 when trying to build an image
with W=1, so it is not triggered by a code change. I don't know
if other architectures are affected. The problem is not seen with
gcc 11.4, but it is seen with gcc 12.3 and 13.2. I did not try
with older versions of gcc.

Bisect log is attached for reference.

The odd error makes me wonder if I should revert to testing with gcc 11.4
and no longer bother with later versions of gcc, at least for any affected
architectures. Any recommendations ?

Thanks,
Guenter

---
# bad: [7ee332c9f12bc5b380e36919cd7d056592a7073f] Merge tag 'parisc-for-6.10-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux
# good: [a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6] Linux 6.9
git bisect start 'HEAD' 'v6.9'
# good: [1b294a1f35616977caddaddf3e9d28e576a1adbc] Merge tag 'net-next-6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
git bisect good 1b294a1f35616977caddaddf3e9d28e576a1adbc
# bad: [d34672777da3ea919e8adb0670ab91ddadf7dea0] Merge tag 'fbdev-for-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev
git bisect bad d34672777da3ea919e8adb0670ab91ddadf7dea0
# bad: [2871ec40994912ce4f2e2d5072a428eb84c77d3c] Merge tag 'drm-misc-next-2024-04-19' of https://gitlab.freedesktop.org/drm/misc/kernel into drm-next
git bisect bad 2871ec40994912ce4f2e2d5072a428eb84c77d3c
# bad: [34633158b8eb8fca145c9a73f8fe4f98c7275b06] Merge tag 'amd-drm-next-6.10-2024-04-13' of https://gitlab.freedesktop.org/agd5f/linux into drm-next
git bisect bad 34633158b8eb8fca145c9a73f8fe4f98c7275b06
# good: [4b0cb230bdb71c23981acfa5e7b367c7dde02a41] drm/amdgpu: retire UMC v12 mca_addr_to_pa
git bisect good 4b0cb230bdb71c23981acfa5e7b367c7dde02a41
# bad: [6376eb8b911534735fec104c1a0d780e4cf3116a] drm/dp: Clarify that wait_hpd_asserted() is not optional for panels
git bisect bad 6376eb8b911534735fec104c1a0d780e4cf3116a
# bad: [9c86b03863844ce69f99aa66404c79492ec9e208] drm/panthor: Fix panthor_devfreq kerneldoc
git bisect bad 9c86b03863844ce69f99aa66404c79492ec9e208
# bad: [b5d7cb76f2674c9d01b611141702723a95d12553] drm: add missing header guards to drm_internal.h
git bisect bad b5d7cb76f2674c9d01b611141702723a95d12553
# good: [4bdca11507928a4c9174e9b7240e9d058c12a71d] drm/panthor: Add the driver frontend block
git bisect good 4bdca11507928a4c9174e9b7240e9d058c12a71d
# good: [b2ec429b69280001d85029dc50b5427af41eb641] drm/tidss: Use dev_err_probe() over dev_dbg() when failing to probe the port
git bisect good b2ec429b69280001d85029dc50b5427af41eb641
# bad: [a61ddb4393ad1be61d2ffd92576d42707b05be17] drm: enable (most) W=1 warnings by default across the subsystem
git bisect bad a61ddb4393ad1be61d2ffd92576d42707b05be17
# good: [113cc3ad8566e06d6c8ef4fc0075a938dedefab5] drm/bridge: Document bridge init order with pre_enable_prev_first
git bisect good 113cc3ad8566e06d6c8ef4fc0075a938dedefab5
# good: [460be1d527a8e296d85301e8b14923299508d4fc] drm/nouveau: move more missing UAPI bits
git bisect good 460be1d527a8e296d85301e8b14923299508d4fc
# first bad commit: [a61ddb4393ad1be61d2ffd92576d42707b05be17] drm: enable (most) W=1 warnings by default across the subsystem