kernel/include/linux/compiler_attributes.h, branch linux-6.1.y

Compiler Attributes: Add __uninitialized macro

2024-07-18T11:18:31Z

commit fd7eea27a3aed79b63b1726c00bde0d50cf207e2 upstream. With INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO enabled the kernel will be compiled with -ftrivial-auto-var-init=<...> which causes initialization of stack variables at function entry time. In order to avoid the performance impact that comes with this users can use the "uninitialized" attribute to prevent such initialization. Therefore provide the __uninitialized macro which can be used for cases where INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO is enabled, but only selected variables should not be initialized. Acked-by: Kees Cook Reviewed-by: Nathan Chancellor Link: https://lore.kernel.org/r/20240205154844.3757121-2-hca@linux.ibm.com Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman

locking: Introduce __cleanup() based infrastructure

2024-02-23T08:12:51Z

commit 54da6a0924311c7cf5015533991e44fb8eb12773 upstream. Use __attribute__((__cleanup__(func))) to build: - simple auto-release pointers using __free() - 'classes' with constructor and destructor semantics for scope-based resource management. - lock guards based on the above classes. Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org Signed-off-by: Greg Kroah-Hartman

Merge tag 'slab-for-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2022-10-10T17:21:22Z

Pull slab fixes from Vlastimil Babka: - The "common kmalloc v4" series [1] by Hyeonggon Yoo. While the plan after LPC is to try again if it's possible to get rid of SLOB and SLAB (and if any critical aspect of those is not possible to achieve with SLUB today, modify it accordingly), it will take a while even in case there are no objections. Meanwhile this is a nice cleanup and some parts (e.g. to the tracepoints) will be useful even if we end up with a single slab implementation in the future: - Improves the mm/slab_common.c wrappers to allow deleting duplicated code between SLAB and SLUB. - Large kmalloc() allocations in SLAB are passed to page allocator like in SLUB, reducing number of kmalloc caches. - Removes the {kmem_cache_alloc,kmalloc}_node variants of tracepoints, node id parameter added to non-_node variants. - Addition of kmalloc_size_roundup() The first two patches from a series by Kees Cook [2] that introduce kmalloc_size_roundup(). This will allow merging of per-subsystem patches using the new function and ultimately stop (ab)using ksize() in a way that causes ongoing trouble for debugging functionality and static checkers. - Wasted kmalloc() memory tracking in debugfs alloc_traces A patch from Feng Tang that enhances the existing debugfs alloc_traces file for kmalloc caches with information about how much space is wasted by allocations that needs less space than the particular kmalloc cache provides. - My series [3] to fix validation races for caches with enabled debugging: - By decoupling the debug cache operation more from non-debug fastpaths, extra locking simplifications were possible and thus done afterwards. - Additional cleanup of PREEMPT_RT specific code on top, by Thomas Gleixner. - A late fix for slab page leaks caused by the series, by Feng Tang. - Smaller fixes and cleanups: - Unneeded variable removals, by ye xingchen - A cleanup removing a BUG_ON() in create_unique_id(), by Chao Yu Link: https://lore.kernel.org/all/20220817101826.236819-1-42.hyeyoo@gmail.com/ [1] Link: https://lore.kernel.org/all/20220923202822.2667581-1-keescook@chromium.org/ [2] Link: https://lore.kernel.org/all/20220823170400.26546-1-vbabka@suse.cz/ [3] * tag 'slab-for-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (30 commits) mm/slub: fix a slab missed to be freed problem slab: Introduce kmalloc_size_roundup() slab: Remove __malloc attribute from realloc functions mm/slub: clean up create_unique_id() mm/slub: enable debugging memory wasting of kmalloc slub: Make PREEMPT_RT support less convoluted mm/slub: simplify __cmpxchg_double_slab() and slab_[un]lock() mm/slub: convert object_map_lock to non-raw spinlock mm/slub: remove slab_lock() usage for debug operations mm/slub: restrict sysfs validation to debug caches and make it safe mm/sl[au]b: check if large object is valid in __ksize() mm/slab_common: move declaration of __ksize() to mm/slab.h mm/slab_common: drop kmem_alloc & avoid dereferencing fields when not using mm/slab_common: unify NUMA and UMA version of tracepoints mm/sl[au]b: cleanup kmem_cache_alloc[_node]_trace() mm/sl[au]b: generalize kmalloc subsystem mm/slub: move free_debug_processing() further mm/sl[au]b: introduce common alloc/free functions without tracepoint mm/slab: kmalloc: pass requests larger than order-1 page to page allocator mm/slab_common: cleanup kmalloc_large() ...

slab: Remove __malloc attribute from realloc functions

2022-09-29T09:05:57Z

The __malloc attribute should not be applied to "realloc" functions, as the returned pointer may alias the storage of the prior pointer. Instead of splitting __malloc from __alloc_size, which would be a huge amount of churn, just create __realloc_size for the few cases where it is needed. Thanks to Geert Uytterhoeven for reporting build failures with gcc-8 in earlier version which tried to remove the #ifdef. While the "alloc_size" attribute is available on all GCC versions, I forgot that it gets disabled explicitly by the kernel in GCC < 9.1 due to misbehaviors. Add a note to the compiler_attributes.h entry for it. Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Vlastimil Babka Cc: Roman Gushchin Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Marco Elver Cc: linux-mm@kvack.org Signed-off-by: Kees Cook Signed-off-by: Vlastimil Babka

net: skb: prevent the split of kfree_skb_reason() by gcc

2022-08-24T08:47:51Z

Sometimes, gcc will optimize the function by spliting it to two or more functions. In this case, kfree_skb_reason() is splited to kfree_skb_reason and kfree_skb_reason.part.0. However, the function/tracepoint trace_kfree_skb() in it needs the return address of kfree_skb_reason(). This split makes the call chains becomes: kfree_skb_reason() -> kfree_skb_reason.part.0 -> trace_kfree_skb() which makes the return address that passed to trace_kfree_skb() be kfree_skb(). Therefore, introduce '__fix_address', which is the combination of '__noclone' and 'noinline', and apply it to kfree_skb_reason() to prevent to from being splited or made inline. (Is it better to simply apply '__noclone oninline' to kfree_skb_reason? I'm thinking maybe other functions have the same problems) Meanwhile, wrap 'skb_unref()' with 'unlikely()', as the compiler thinks it is likely return true and splits kfree_skb_reason(). Signed-off-by: Menglong Dong Signed-off-by: David S. Miller

Compiler Attributes: Add __diagnose_as for Clang

2022-02-14T00:50:07Z

Clang will perform various compile-time diagnostics on uses of various functions (e.g. simple bounds-checking on strcpy(), etc). These diagnostics can be assigned to other functions (for example, new implementations of the string functions under CONFIG_FORTIFY_SOURCE) using the "diagnose_as_builtin" attribute. This allows those functions to retain their compile-time diagnostic warnings. Cc: Nathan Chancellor Cc: llvm@lists.linux.dev Reviewed-by: Miguel Ojeda Reviewed-by: Nick Desaulniers Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220208225350.1331628-5-keescook@chromium.org

Compiler Attributes: Add __overloadable for Clang

2022-02-14T00:50:07Z

In order for FORTIFY_SOURCE to use __pass_object_size on an "extern inline" function, as all the fortified string functions are, the functions must be marked as being overloadable (i.e. different prototypes due to the implicitly injected object size arguments). This allows the __pass_object_size versions to take precedence. Cc: Nathan Chancellor Cc: llvm@lists.linux.dev Reviewed-by: Miguel Ojeda Reviewed-by: Nick Desaulniers Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220208225350.1331628-4-keescook@chromium.org

Compiler Attributes: Add __pass_object_size for Clang

2022-02-14T00:50:06Z

In order to gain greater visibility to type information when using __builtin_object_size(), Clang has a function attribute "pass_object_size" that will make size information available for marked arguments in a function by way of implicit additional function arguments that are then wired up the __builtin_object_size(). This is needed to implement FORTIFY_SOURCE in Clang, as a workaround to Clang's __builtin_object_size() having limited visibility[1] into types across function calls (even inlines). This attribute has an additional benefit that it can be used even on non-inline functions to gain argument size information. [1] https://github.com/llvm/llvm-project/issues/53516 Cc: Nick Desaulniers Cc: Nathan Chancellor Cc: llvm@lists.linux.dev Reviewed-by: Miguel Ojeda Signed-off-by: Kees Cook Reviewed-by: Nick Desaulniers Link: https://lore.kernel.org/r/20220208225350.1331628-3-keescook@chromium.org

compiler_attributes.h: Add __disable_sanitizer_instrumentation

2021-12-10T00:42:28Z

The new attribute maps to __attribute__((disable_sanitizer_instrumentation)), which will be supported by Clang >= 14.0. Future support in GCC is also possible. This attribute disables compiler instrumentation for kernel sanitizer tools, making it easier to implement noinstr. It is different from the existing __no_sanitize* attributes, which may still allow certain types of instrumentation to prevent false positives. Signed-off-by: Alexander Potapenko Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

Merge tag 'compiler-attributes-for-linus-v5.16' of git://github.com/ojeda/linux

2021-11-07T18:38:17Z

Pull compiler attributes update from Miguel Ojeda: "An improvement for `__compiletime_assert` and a trivial cleanup" * tag 'compiler-attributes-for-linus-v5.16' of git://github.com/ojeda/linux: compiler_types: mark __compiletime_assert failure as __noreturn Compiler Attributes: remove GCC 5.1 mention