Hi, On Sun, Feb 14, 2021 at 09:41:27PM +0100, Luc Van Oostenryck wrote: > On Sun, Feb 14, 2021 at 11:00:48AM -0800, Linus Torvalds wrote: > > On Sun, Feb 14, 2021 at 10:42 AM Ramsay Jones > > <ram...@ramsayjones.plus.com> wrote: > > > > > > > > > > > I looked around but didn't find any hints how to fix this. Any pointers > > > > I missed (added the sparse list to cc:)? > > > > > > This is a limitation of sparse; when using the 'stringize' pre-processor > > > operator #, the maximum size of the resulting string is about 8k (if I > > > remember correctly). > > > > Well, yes and no. > > > > The C89 standard actually says that a string literal can be at most > > 509 characters to be portable. C99 increased it to 4095 characters. > > > > Sparse makes the limit higher, and the limit could easily be expanded > > way past 8kB - but the point is that large string literals are > > actually not guaranteed to be valid C. > > > > So honestly, it really sounds like that TRACE_EVENT() thing is doing > > something it shouldn't be doing. > > In itself, it's OKish but it does a lot of macro expansions and most > arguments are macros of macros of ... but the problem seems to be > limited to TP_printk(). > > In the current case, the offender is the string 'print_fmt_tps6598x_status' > which is just under 26K long especially because it expand > TPS6598X_STATUS_FLAGS_MASK but also because the arguments use FIELD_GET() > and thus __BF_FIELD_CHECK().
That was a great hint! Using a custom FIELD_GET() that drops the __BF_FIELD_CHECK() makes things fit. Cheers, -- Guido > > > > I don't think there's any fundamental limit why sparse does 8kB as a > > limit (just a few random buffers). Making sparse accept larger ones > > should be as simple as just increasing MAX_STRING, but I really don't > > think the kernel should encourage that kind of excessive string sizes. > > Like you noted, there are just a few cases in the kernel and IIRC > there is or was one case in it too. > I would tend to increase MAX_STRING to something like 32 or 64K, > in order to keep it reasonable but let sparse to continue its processing, > but add a warning when the string/token is bigger than the current 8K. > > -- Luc >
