On Mon, Feb 08, 2021 at 01:48:06PM +0000, David Laight wrote: > From: Sasha Levin > > Sent: 06 February 2021 03:51 > > > > Right now if SUBLEVEL becomes larger than 255 it will overflow into the > > territory of PATCHLEVEL, causing havoc in userspace that tests for > > specific kernel version. > > > > While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test > > SUBLEVEL at any point as ABI changes don't happen in the context of > > stable tree. > > > > Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in > > the context of LINUX_VERSION_CODE. This does not affect "make > > kernelversion" and such. > > > > Signed-off-by: Sasha Levin <sas...@kernel.org> > > --- > > Makefile | 12 +++++++++--- > > 1 file changed, 9 insertions(+), 3 deletions(-) > > > > diff --git a/Makefile b/Makefile > > index 49ac1b7fe8e99..157be50c691e5 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h > > endef > > > > define filechk_version.h > > - echo \#define LINUX_VERSION_CODE $(shell \ > > - expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \ > > - echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' > > + if [ $(SUBLEVEL) -gt 255 ]; then \ > > + echo \#define LINUX_VERSION_CODE $(shell \ > > + expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \ > > + else \ > > + echo \#define LINUX_VERSION_CODE $(shell \ > > + expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + > > $(SUBLEVEL)); \ > > + fi; \ > > + echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + \ > > + ((c) > 255 ? 255 : (c)))' > > endef > > Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ? > Basically just: > echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), > $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'
Because we are "clamping" LINUX_VERSION_CODE() at a x.y.255, while KERNEL_VERSION() continues on with the "real" minor number. thanks, greg k-h
