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Subject[PATCH AUTOSEL 5.10 34/36] ubsan: implement __ubsan_handle_alignment_assumption
Date
From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit 28abcc963149e06d956d95a18a85f4ba26af746f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/ubsan.c | 31 +++++++++++++++++++++++++++++++
lib/ubsan.h | 6 ++++++
2 files changed, 37 insertions(+)

diff --git a/lib/ubsan.c b/lib/ubsan.c
index cb9af3f6b77e3..adf8dcf3c84e6 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 7b56c09473a98..9a0b71c5ff9fb 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;
--
2.27.0
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