linux-kernel - [PATCH 1/1] alloc_tag: work around clang-14 issue with __builtin_object

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Message-ID: <20250201200503.2532357-1-surenb@google.com>
Date: Sat,  1 Feb 2025 12:05:03 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, nathan@...nel.org, ndesaulniers@...gle.com, 
	keescook@...omium.org, morbo@...gle.com, justinstitt@...gle.com, 
	surenb@...gle.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, kernel test robot <lkp@...el.com>
Subject: [PATCH 1/1] alloc_tag: work around clang-14 issue with __builtin_object_size()

Additional condition in the allocation hooks causes Clang version 14
(tested on 14.0.6) to treat the allocated object size as unknown at
compile-time (__builtin_object_size(obj, 1) returns -1) even though
both branches of that condition yield the same result. Other versions
of Clang (tested with 13.0.1, 15.0.7, 16.0.6 and 17.0.6) compile the
same code without issues. Add build-time Clang version check which
removes this condition and effectively restores the unconditional tag
store/restore flow when compiled with clang-14.

Fixes: 07438779313c ("alloc_tag: avoid current->alloc_tag manipulations when profiling is disabled")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501310832.kiAeOt2z-lkp@intel.com/
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 include/linux/alloc_tag.h | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index a946e0203e6d..df432c2c3483 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -222,10 +222,23 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
 
 #endif /* CONFIG_MEM_ALLOC_PROFILING */
 
+/* See https://lore.kernel.org/all/202501310832.kiAeOt2z-lkp@intel.com/ */
+#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION >= 140000 && CONFIG_CLANG_VERSION < 150000
+static inline bool store_current_tag(void)
+{
+	return true;
+}
+#else
+static inline bool store_current_tag(void)
+{
+	return mem_alloc_profiling_enabled();
+}
+#endif
+
 #define alloc_hooks_tag(_tag, _do_alloc)				\
 ({									\
 	typeof(_do_alloc) _res;						\
-	if (mem_alloc_profiling_enabled()) {				\
+	if (store_current_tag()) {					\
 		struct alloc_tag * __maybe_unused _old;			\
 		_old = alloc_tag_save(_tag);				\
 		_res = _do_alloc;					\

base-commit: 60c828cf80c07394762a1edfaff63bea55cc8e45
-- 
2.48.1.362.g079036d154-goog