Avoid nested min()/max() which results in egregious macro expansion.
This issue was introduced by commit 867046cc7027 ("minmax: relax check to
allow comparison between unsigned arguments and signed constants") [0].
Work has been done to address the issue of egregious min()/max() macro
expansion in commit 22f546873149 ("minmax: improve macro expansion and type
checking") and related, however it appears that some issues remain on more
tightly constrained systems.
Adjust a few known-bad cases of deeply nested macros to avoid doing so to
mitigate this. Porting the patch first proposed in [1] to Linus's tree.
Note that we use clamp_t() rather than clamp() when we otherwise could use
the latter because it isn't certain than the clamp() won't expand into a
more egregiously huge form, certainly prior to the recent fixes.
Running an allmodconfig build using the methodology described in [2] we
observe a 35 MiB reduction in generated code.
The difference is much more significant prior to recent minmax fixes which
were not backported. As per [1] prior these the reduction is more like 200
MiB.
This resolves an issue with slackware 15.0 32-bit compilation as reported
by Richard Narron.
Presumably the min/max fixups would be difficult to backport, this series
should be easier and fix's Richard's problem in 5.15.
[0]:https://lore.kernel.org/all/b97faef60ad24922b530241c5d7c933c@xxxxxxxxxxxxxxxx/
[1]:https://lore.kernel.org/lkml/5882b96e-1287-4390-8174-3316d39038ef@lucifer.local/
[2]:https://lore.kernel.org/linux-mm/36aa2cad-1db1-4abf-8dd2-fb20484aabc3@lucifer.local/
v2:
* Split into separate patches to make backporting easier.
* Corrected type in sDIGIT_FITTING() argument.
* Added reviewed-by tags.
v1:
https://lore.kernel.org/all/20240911153457.1005227-1-lorenzo.stoakes@xxxxxxxxxx/
Lorenzo Stoakes (3):
minmax: reduce min/max macro expansion in mvpp2 driver
minmax: reduce min/max macro expansion in skbuff
minmax: reduce min/max macro expansion in atomisp driver
drivers/net/ethernet/marvell/mvpp2/mvpp2.h | 2 +-
.../staging/media/atomisp/pci/sh_css_frac.h | 26 ++++++++++++++-----
include/linux/skbuff.h | 6 ++++-
3 files changed, 25 insertions(+), 9 deletions(-)
--
2.46.0
