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@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 3e3352f3d0da7b9e9f764bf7eb106463872f0a3e..bec38c64d6a624fe5680cff59bdc1a0b9dc7d803 100644 (file)
--- 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 7b56c09473a98e7fcff4c8e6640459d1d178c49c..9a0b71c5ff9fbf45492c0043f24a8578f06acaf6 100644 (file)
--- 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;