From: Nathan Chancellor <nathan@xxxxxxxxxx> Subject: ubsan: implement __ubsan_handle_alignment_assumption 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 Link: https://lkml.kernel.org/r/20210127224451.2587372-1-nathan@xxxxxxxxxx Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/ubsan.c | 31 +++++++++++++++++++++++++++++++ lib/ubsan.h | 6 ++++++ 2 files changed, 37 insertions(+) --- a/lib/ubsan.c~ubsan-implement-__ubsan_handle_alignment_assumption +++ a/lib/ubsan.c @@ -427,3 +427,34 @@ void __ubsan_handle_load_invalid_value(v 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); --- a/lib/ubsan.h~ubsan-implement-__ubsan_handle_alignment_assumption +++ a/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; _
