Messages in this thread | | | From | Nick Desaulniers <> | Date | Wed, 27 Jan 2021 14:54:37 -0800 | Subject | Re: [PATCH v3] ubsan: Implement __ubsan_handle_alignment_assumption |
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On Wed, Jan 27, 2021 at 2:46 PM Nathan Chancellor <nathan@kernel.org> 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 > Acked-by: Kees Cook <keescook@chromium.org> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> --- > > v2 -> v3: > > * Add prototype right above definition to avoid introducing a warning > with W=1. > > v1 -> v2: > > * Use __ffs instead of ffs because due to size of input (unsigned long > vs int) and we want a zero based index (Nick Desaulniers). > > * Pick up Kees's ack. > > lib/ubsan.c | 31 +++++++++++++++++++++++++++++++ > lib/ubsan.h | 6 ++++++ > 2 files changed, 37 insertions(+) > > diff --git a/lib/ubsan.c b/lib/ubsan.c > index 3e3352f3d0da..bec38c64d6a6 100644 > --- a/lib/ubsan.c > +++ b/lib/ubsan.c > @@ -427,3 +427,34 @@ 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); > +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(real_ptr ? __ffs(real_ptr) : 0), > + 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: 6ee1d745b7c9fd573fba142a2efdad76a9f1cb04 > -- > 2.30.0 >
-- Thanks, ~Nick Desaulniers
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