From: kernel test robot <lkp@intel.com>
To: elver@google.com
Cc: oe-kbuild-all@lists.linux.dev
Subject: [melver:ctx-analysis/dev 19/35] include/linux/cleanup.h:554:73: warning: cast to generic address space pointer from disjoint '__seg_fs' address space pointer
Date: Wed, 17 Dec 2025 11:54:08 +0800 [thread overview]
Message-ID: <202512171127.RpZhinvv-lkp@intel.com> (raw)
tree: https://git.kernel.org/pub/scm/linux/kernel/git/melver/linux.git ctx-analysis/dev
head: ce5acac3089f2dd72a384cbcd3f0e4ec28e9cf29
commit: 55ba795143c3f548c5d0d7ead143ebea3ee8405c [19/35] locking/local_lock: Support Clang's context analysis
config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20251217/202512171127.RpZhinvv-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251217/202512171127.RpZhinvv-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512171127.RpZhinvv-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from include/linux/jump_label.h:78,
from include/linux/dynamic_debug.h:6,
from include/linux/printk.h:621,
from include/asm-generic/bug.h:31,
from arch/x86/include/asm/bug.h:193,
from arch/x86/include/asm/alternative.h:9,
from arch/x86/include/asm/barrier.h:5,
from include/asm-generic/bitops/generic-non-atomic.h:7,
from include/linux/bitops.h:28,
from include/linux/kernel.h:23,
from include/linux/bit_spinlock.h:5,
from lib/test_context-analysis.c:7:
lib/test_context-analysis.c: In function 'test_local_lock_guard':
>> include/linux/cleanup.h:554:73: warning: cast to generic address space pointer from disjoint '__seg_fs' address space pointer
554 | *__UNIQUE_ID(unlock) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
| ^
include/linux/local_lock.h:108:42: note: in expansion of macro 'WITH_LOCK_GUARD_1_ATTRS'
108 | #define class_local_lock_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock, _T)
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/cleanup.h:300:17: note: in expansion of macro 'class_local_lock_constructor'
300 | class_##_name##_constructor
| ^~~~~~
include/linux/cleanup.h:419:9: note: in expansion of macro 'CLASS'
419 | CLASS(_name, __UNIQUE_ID(guard))
| ^~~~~
lib/test_context-analysis.c:502:11: note: in expansion of macro 'guard'
502 | { guard(local_lock)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
| ^~~~~
>> include/linux/cleanup.h:554:73: warning: cast to generic address space pointer from disjoint '__seg_fs' address space pointer
554 | *__UNIQUE_ID(unlock) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
| ^
include/linux/local_lock.h:110:46: note: in expansion of macro 'WITH_LOCK_GUARD_1_ATTRS'
110 | #define class_local_lock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_irq, _T)
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/cleanup.h:300:17: note: in expansion of macro 'class_local_lock_irq_constructor'
300 | class_##_name##_constructor
| ^~~~~~
include/linux/cleanup.h:419:9: note: in expansion of macro 'CLASS'
419 | CLASS(_name, __UNIQUE_ID(guard))
| ^~~~~
lib/test_context-analysis.c:503:11: note: in expansion of macro 'guard'
503 | { guard(local_lock_irq)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
| ^~~~~
>> include/linux/cleanup.h:554:73: warning: cast to generic address space pointer from disjoint '__seg_fs' address space pointer
554 | *__UNIQUE_ID(unlock) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
| ^
include/linux/local_lock.h:112:50: note: in expansion of macro 'WITH_LOCK_GUARD_1_ATTRS'
112 | #define class_local_lock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_irqsave, _T)
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/cleanup.h:300:17: note: in expansion of macro 'class_local_lock_irqsave_constructor'
300 | class_##_name##_constructor
| ^~~~~~
include/linux/cleanup.h:419:9: note: in expansion of macro 'CLASS'
419 | CLASS(_name, __UNIQUE_ID(guard))
| ^~~~~
lib/test_context-analysis.c:504:11: note: in expansion of macro 'guard'
504 | { guard(local_lock_irqsave)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
| ^~~~~
>> include/linux/cleanup.h:554:73: warning: cast to generic address space pointer from disjoint '__seg_fs' address space pointer
554 | *__UNIQUE_ID(unlock) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
| ^
include/linux/local_lock.h:114:52: note: in expansion of macro 'WITH_LOCK_GUARD_1_ATTRS'
114 | #define class_local_lock_nested_bh_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_nested_bh, _T)
| ^~~~~~~~~~~~~~~~~~~~~~~
include/linux/cleanup.h:300:17: note: in expansion of macro 'class_local_lock_nested_bh_constructor'
300 | class_##_name##_constructor
| ^~~~~~
include/linux/cleanup.h:419:9: note: in expansion of macro 'CLASS'
419 | CLASS(_name, __UNIQUE_ID(guard))
| ^~~~~
lib/test_context-analysis.c:505:11: note: in expansion of macro 'guard'
505 | { guard(local_lock_nested_bh)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
| ^~~~~
vim +/__seg_fs +554 include/linux/cleanup.h
5acc03642ea67f Marco Elver 2025-01-17 518
5acc03642ea67f Marco Elver 2025-01-17 519 /*
5acc03642ea67f Marco Elver 2025-01-17 520 * To support Context Analysis, we need to allow the compiler to see the
5acc03642ea67f Marco Elver 2025-01-17 521 * acquisition and release of the context lock. However, the "cleanup" helpers
5acc03642ea67f Marco Elver 2025-01-17 522 * wrap the lock in a struct passed through seperate helper functions, which
5acc03642ea67f Marco Elver 2025-01-17 523 * hides the lock alias from the compiler (no inter-procedural analysis).
5acc03642ea67f Marco Elver 2025-01-17 524 *
5acc03642ea67f Marco Elver 2025-01-17 525 * To make it work, we introduce an explicit alias to the context lock instance
5acc03642ea67f Marco Elver 2025-01-17 526 * that is "cleaned" up with a separate cleanup helper. This helper is a dummy
5acc03642ea67f Marco Elver 2025-01-17 527 * function that does nothing at runtime, but has the "_unlock" attribute to
5acc03642ea67f Marco Elver 2025-01-17 528 * tell the compiler what happens at the end of the scope.
5acc03642ea67f Marco Elver 2025-01-17 529 *
5acc03642ea67f Marco Elver 2025-01-17 530 * To generalize the pattern, the WITH_LOCK_GUARD_1_ATTRS() macro should be used
5acc03642ea67f Marco Elver 2025-01-17 531 * to redefine the constructor, which then also creates the alias variable with
5acc03642ea67f Marco Elver 2025-01-17 532 * the right "cleanup" attribute, *after* DECLARE_LOCK_GUARD_1_ATTRS() has been
5acc03642ea67f Marco Elver 2025-01-17 533 * used.
5acc03642ea67f Marco Elver 2025-01-17 534 *
5acc03642ea67f Marco Elver 2025-01-17 535 * Example usage:
5acc03642ea67f Marco Elver 2025-01-17 536 *
5acc03642ea67f Marco Elver 2025-01-17 537 * DECLARE_LOCK_GUARD_1_ATTRS(mutex, __acquires(_T), __releases(*(struct mutex **)_T))
5acc03642ea67f Marco Elver 2025-01-17 538 * #define class_mutex_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(mutex, _T)
5acc03642ea67f Marco Elver 2025-01-17 539 *
5acc03642ea67f Marco Elver 2025-01-17 540 * Note: To support the for-loop based scoped helpers, the auxiliary variable
5acc03642ea67f Marco Elver 2025-01-17 541 * must be a pointer to the "class" type because it is defined in the same
5acc03642ea67f Marco Elver 2025-01-17 542 * statement as the guard variable. However, we initialize it with the lock
5acc03642ea67f Marco Elver 2025-01-17 543 * pointer (despite the type mismatch, the compiler's alias analysis still works
5acc03642ea67f Marco Elver 2025-01-17 544 * as expected). The "_unlock" attribute receives a pointer to the auxiliary
5acc03642ea67f Marco Elver 2025-01-17 545 * variable (a double pointer to the class type), and must be cast and
5acc03642ea67f Marco Elver 2025-01-17 546 * dereferenced appropriately.
5acc03642ea67f Marco Elver 2025-01-17 547 */
5acc03642ea67f Marco Elver 2025-01-17 548 #define DECLARE_LOCK_GUARD_1_ATTRS(_name, _lock, _unlock) \
5acc03642ea67f Marco Elver 2025-01-17 549 static inline class_##_name##_t class_##_name##_constructor(lock_##_name##_t *_T) _lock;\
5acc03642ea67f Marco Elver 2025-01-17 550 static __always_inline void __class_##_name##_cleanup_ctx(class_##_name##_t **_T) \
5acc03642ea67f Marco Elver 2025-01-17 551 __no_context_analysis _unlock { }
5acc03642ea67f Marco Elver 2025-01-17 552 #define WITH_LOCK_GUARD_1_ATTRS(_name, _T) \
5acc03642ea67f Marco Elver 2025-01-17 553 class_##_name##_constructor(_T), \
5acc03642ea67f Marco Elver 2025-01-17 @554 *__UNIQUE_ID(unlock) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
5acc03642ea67f Marco Elver 2025-01-17 555
:::::: The code at line 554 was first introduced by commit
:::::: 5acc03642ea67f590f3c0995602631339d26ec01 cleanup: Basic compatibility with context analysis
:::::: TO: Marco Elver <elver@google.com>
:::::: CC: Marco Elver <elver@google.com>
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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