On 2/12/23 6:21 AM, kernel test robot wrote: > Hi Dave, > > Thank you for the patch! Perhaps something to improve: > > [auto build test WARNING on bpf-next/master] > > url: https://github.com/intel-lab-lkp/linux/commits/Dave-Marchevsky/bpf-Migrate-release_on_unlock-logic-to-non-owning-ref-semantics/20230212-172813 > base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master > patch link: https://lore.kernel.org/r/20230212092715.1422619-4-davemarchevsky%40fb.com > patch subject: [PATCH v5 bpf-next 3/9] bpf: Add bpf_rbtree_{add,remove,first} kfuncs > config: hexagon-randconfig-r045-20230212 (https://download.01.org/0day-ci/archive/20230212/202302121936.t36vlAFG-lkp@xxxxxxxxx/config ) > compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project db0e6591612b53910a1b366863348bdb9d7d2fb1) > reproduce (this is a W=1 build): > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # https://github.com/intel-lab-lkp/linux/commit/39ccb1ecaa4f95d55dfd9ba495ecefe3fe1f6982 > git remote add linux-review https://github.com/intel-lab-lkp/linux > git fetch --no-tags linux-review Dave-Marchevsky/bpf-Migrate-release_on_unlock-logic-to-non-owning-ref-semantics/20230212-172813 > git checkout 39ccb1ecaa4f95d55dfd9ba495ecefe3fe1f6982 > # save the config file > mkdir build_dir && cp config build_dir/.config > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon olddefconfig > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash kernel/bpf/ > > If you fix the issue, kindly add following tag where applicable > | Reported-by: kernel test robot <lkp@xxxxxxxxx> > | Link: https://lore.kernel.org/oe-kbuild-all/202302121936.t36vlAFG-lkp@xxxxxxxxx/ > > All warnings (new ones prefixed by >>): > > In file included from kernel/bpf/helpers.c:4: > In file included from include/linux/bpf.h:31: > In file included from include/linux/memcontrol.h:13: > In file included from include/linux/cgroup.h:26: > In file included from include/linux/kernel_stat.h:9: > In file included from include/linux/interrupt.h:11: > In file included from include/linux/hardirq.h:11: > In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1: > In file included from include/asm-generic/hardirq.h:17: > In file included from include/linux/irq.h:20: > In file included from include/linux/io.h:13: > In file included from arch/hexagon/include/asm/io.h:334: > include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > val = __raw_readb(PCI_IOBASE + addr); > ~~~~~~~~~~ ^ > include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr)); > ~~~~~~~~~~ ^ > include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu' > #define __le16_to_cpu(x) ((__force __u16)(__le16)(x)) > ^ > In file included from kernel/bpf/helpers.c:4: > In file included from include/linux/bpf.h:31: > In file included from include/linux/memcontrol.h:13: > In file included from include/linux/cgroup.h:26: > In file included from include/linux/kernel_stat.h:9: > In file included from include/linux/interrupt.h:11: > In file included from include/linux/hardirq.h:11: > In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1: > In file included from include/asm-generic/hardirq.h:17: > In file included from include/linux/irq.h:20: > In file included from include/linux/io.h:13: > In file included from arch/hexagon/include/asm/io.h:334: > include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr)); > ~~~~~~~~~~ ^ > include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu' > #define __le32_to_cpu(x) ((__force __u32)(__le32)(x)) > ^ > In file included from kernel/bpf/helpers.c:4: > In file included from include/linux/bpf.h:31: > In file included from include/linux/memcontrol.h:13: > In file included from include/linux/cgroup.h:26: > In file included from include/linux/kernel_stat.h:9: > In file included from include/linux/interrupt.h:11: > In file included from include/linux/hardirq.h:11: > In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1: > In file included from include/asm-generic/hardirq.h:17: > In file included from include/linux/irq.h:20: > In file included from include/linux/io.h:13: > In file included from arch/hexagon/include/asm/io.h:334: > include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > __raw_writeb(value, PCI_IOBASE + addr); > ~~~~~~~~~~ ^ > include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr); > ~~~~~~~~~~ ^ > include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] > __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr); > ~~~~~~~~~~ ^ >>> kernel/bpf/helpers.c:1901:9: warning: cast from 'bool (*)(struct bpf_rb_node *, const struct bpf_rb_node *)' (aka '_Bool (*)(struct bpf_rb_node *, const struct bpf_rb_node *)') to 'bool (*)(struct rb_node *, const struct rb_node *)' (aka '_Bool (*)(struct rb_node *, const struct rb_node *)') converts to incompatible function type [-Wcast-function-type-strict] > (bool (*)(struct rb_node *, const struct rb_node *))less); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This is the only new warning introduced by this series. A previous version had the same complaint by kernel test robot. struct bpf_rb_node is an opaque struct with the same size as struct rb_node. It's not intended to be manipulated directly by any BPF program or bpf-rbtree kernel code, but rather to be used as a struct rb_node by rbtree library helpers. Here, the compiler complains that the less() callback taken by bpf_rbtree_add is typed bool (*)(struct bpf_rb_node *, const struct bpf_rb_node *) while the actual rbtree lib helper rb_add's less() is typed bool (*)(struct rb_node *, const struct rb_node *) I'm not a C standard expert, but based on my googling, for C99 it's not valid to cast a function pointer to anything aside from void* and its original type. Furthermore, since struct bpf_rb_node an opaque bitfield and struct rb_node has actual members, C99 standard 6.2.7 paragraph 1 states that they're not compatible: Moreover, two structure, union, or enumerated types declared in separate translation units are compatible if their tags and members satisfy the following requirements: If one is declared with a tag, the other shall be declared with the same tag. If both are complete types, then the following additional requirements apply: there shall be a one-to-one correspondence between their members such that each pair of corresponding members are declared with compatible types, and such that if one member of a corresponding pair is declared with a name, the other member is declared with the same name. For two structures, corresponding members shall be declared in the same order I'm not sure how to proceed here. We could change bpf_rbtree_add's less() cb to take two rb_node *'s, but then each such cb implementation would have to cast its parameters before doing anything useful with them. Furthermore this would require introducing non-opaque rb_node type into BPF programs. Other ideas seem similarly hacky. Note that this flag was only recently introduced [0] and discussion in that linked thread notes that ~1500 other places in the kernel raise same warning. [0]: https://reviews.llvm.org/D134831 > 7 warnings generated. > > > vim +1901 kernel/bpf/helpers.c > > 1896 > 1897 void bpf_rbtree_add(struct bpf_rb_root *root, struct bpf_rb_node *node, > 1898 bool (less)(struct bpf_rb_node *a, const struct bpf_rb_node *b)) > 1899 { > 1900 rb_add_cached((struct rb_node *)node, (struct rb_root_cached *)root, >> 1901 (bool (*)(struct rb_node *, const struct rb_node *))less); > 1902 } > 1903 >
