On Tue, Jan 12, 2021 at 01:15:42PM -0800, Nick Desaulniers wrote: > On Tue, Jan 12, 2021 at 12:55 PM Nathan Chancellor > <[email protected]> wrote: > > > > When building ARCH=mips 32r2el_defconfig with CONFIG_UBSAN_ALIGNMENT: > > > > ld.lld: error: undefined symbol: __ubsan_handle_alignment_assumption > > >>> referenced by slab.h:557 (include/linux/slab.h:557) > > >>> main.o:(do_initcalls) in archive init/built-in.a > > >>> referenced by slab.h:448 (include/linux/slab.h:448) > > >>> do_mounts_rd.o:(rd_load_image) in archive init/built-in.a > > >>> referenced by slab.h:448 (include/linux/slab.h:448) > > >>> do_mounts_rd.o:(identify_ramdisk_image) in archive > > >>> init/built-in.a > > >>> referenced 1579 more times > > > > Implement this for the kernel based on LLVM's > > handleAlignmentAssumptionImpl because the kernel is not linked against > > the compiler runtime. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1245 > > Link: > > https://github.com/llvm/llvm-project/blob/llvmorg-11.0.1/compiler-rt/lib/ubsan/ubsan_handlers.cpp#L151-L190 > > Signed-off-by: Nathan Chancellor <[email protected]> > > --- > > lib/ubsan.c | 28 ++++++++++++++++++++++++++++ > > lib/ubsan.h | 6 ++++++ > > 2 files changed, 34 insertions(+) > > > > diff --git a/lib/ubsan.c b/lib/ubsan.c > > index 3e3352f3d0da..a1e6cc9993f8 100644 > > --- a/lib/ubsan.c > > +++ b/lib/ubsan.c > > @@ -427,3 +427,31 @@ void __ubsan_handle_load_invalid_value(void *_data, > > void *val) > > ubsan_epilogue(); > > } > > EXPORT_SYMBOL(__ubsan_handle_load_invalid_value); > > + > > +void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr, > > + unsigned long align, > > + unsigned long offset) > > +{ > > + struct alignment_assumption_data *data = _data; > > + unsigned long real_ptr; > > + > > + if (suppress_report(&data->location)) > > + return; > > + > > + ubsan_prologue(&data->location, "alignment-assumption"); > > + > > + if (offset) > > + pr_err("assumption of %lu byte alignment (with offset of > > %lu byte) for pointer of type %s failed", > > + align, offset, data->type->type_name); > > + else > > + pr_err("assumption of %lu byte alignment for pointer of > > type %s failed", > > + align, data->type->type_name); > > + > > + real_ptr = ptr - offset; > > + pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes", > > + offset ? "offset " : "", BIT(ffs(real_ptr)), > > if real_ptr is an unsigned long, do we want to use `__ffs(real_ptr) + > 1` here rather than ffs which takes an int? It seems the kernel is > missing a definition of ffsl. :(
Why the + 1? I think if we use __ffs (which it seems like we should), I think that needs to become BIT(real_ptr ? __ffs(real_ptr) : 0) I have made that change locally and will send it for v2 in a day or so to give Kees some time to check it out. Thanks for the review! Nathan
