Messages in this thread | | | Date | Thu, 31 May 2018 05:09:21 -0700 (PDT) | Subject | Re: [PATCH] riscv: pass machine size to sparse | From | Palmer Dabbelt <> |
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On Mon, 28 May 2018 23:14:20 PDT (-0700), yamada.masahiro@socionext.com wrote: > 2018-05-29 15:11 GMT+09:00 Christoph Hellwig <hch@infradead.org>: >> On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote: >>> By default, sparse assumes a 64bit machine when compiled on x86-64 >>> and 32bit when compiled on anything else. >>> >>> This can of course create all sort of problems when this doesn't >>> correspond to the target's machine size, like issuing false >>> warnings like: 'shift too big (32) for type unsigned long' or >>> is 64bit while sparse was compiled on a 32bit machine, or worse, >>> to not emit legitimate warnings. >>> >>> Fix this by passing the appropriate -m32/-m64 flag to sparse. >> >> Can we please move this to the common Kbuild code using the >> CONFIG_64BIT syombol? This really should not need boiler plate in >> every architecture. > > > I agree. > > Luc did so for -mbig/little-endian: > https://patchwork.kernel.org/patch/10433957/ > > We should do likewise for -m32/64.
Sorry for being a bit slow here, but I like the idea of making the 32/64-bit issue generic as it seems like it'll be necessary for every port. Looking through the patch for big/little-endian I did notice:
* RISC-V compilers set "__riscv_xlen" to the length of an X (integer) register in bits. * RISC-V compilers define "__riscv", and it doesn't appear we inform sparse about that.
These two might not be that interesting, but we do already have some cases where we're checking for __riscv_xlen in Linux. I've yet to successfully use sparse, but adding at least
CHECKFLAGS += -D__riscv
seems reasonable, and possibly also some sort of
ifeq ($(CONFIG_ARCH_RV64I),y) CHECKFLAGS += -D__riscv_xlen=64 else CHECKFLAGS += -D__riscv_xlen=32 fi
might be necessary. We strive to follow the generic rules for ABI-related stuff like __LP64__ but I don't think there's any generic mapping for XLEN. Similarly there's "__riscv_flen" and "__riscv_float_abi_*", but those are less likely to be used by the kernel so they're probably not worth worrying about for now.
There's also a bunch of other RISC-V macros, the only one of which we're currently using is "__riscv_muldiv" (and that's in a manner that's unlikely to trigger any sort of static analysis). Between a lack of Kconfig options and a glibc port we're essentially mandating IMA right now, so these probably don't matter.
Thanks!
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