On Tue, Jan 12, 2021 at 12:55 PM Nathan Chancellor <natechancel...@gmail.com> 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 <natechancel...@gmail.com> > --- > 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. :( Otherwise code LGTM. > + real_ptr & (align - 1)); > + > + ubsan_epilogue(); > +} > +EXPORT_SYMBOL(__ubsan_handle_alignment_assumption); > diff --git a/lib/ubsan.h b/lib/ubsan.h > index 7b56c09473a9..9a0b71c5ff9f 100644 > --- a/lib/ubsan.h > +++ b/lib/ubsan.h > @@ -78,6 +78,12 @@ struct invalid_value_data { > struct type_descriptor *type; > }; > > +struct alignment_assumption_data { > + struct source_location location; > + struct source_location assumption_location; > + struct type_descriptor *type; > +}; > + > #if defined(CONFIG_ARCH_SUPPORTS_INT128) > typedef __int128 s_max; > typedef unsigned __int128 u_max; > > base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837 > -- > 2.30.0 > -- Thanks, ~Nick Desaulniers