Don't sanitize linker_set

[matthew.bryan_isilon.com]

Summary

The assumptions of linker_set don't play nicely with AddressSanitizer. AddressSanitizer adds a 'redzone' of zeros around globals (including those in named sections), whereas linker_set assumes they are all packed consecutively like a pointer array. So: let's annotate linker_set so that AddressSanitizer ignores it.

Adding Konstantin to the review as somebody who touched linker_set recently.

Test Plan

Manual testing to demonstrate that linker_set pointers are consecutive with no redzone. Compiled and ran the kernel and ran few kyua tests for sanity.

[kib]

sys/sys/linker_set.h

65 ↗

(On Diff #63949)

I prefer that you put the new attribute after __used.

head/sys/sys/cdefs.h

 #define __requires_shared(...) \
         __lock_annotate(shared_locks_required(__VA_ARGS__))
 #define __requires_unlocked(...) \
         __lock_annotate(locks_excluded(__VA_ARGS__))
 
 /* Function should not be analyzed. */
 #define __no_lock_analysis      __lock_annotate(no_thread_safety_analysis)
 
+/* Function or variable should not be sanitized, ie. by AddressSanitizer */
+#if __has_attribute(no_sanitize)
+#define __nosanitizeaddress     __attribute__((no_sanitize("address")))
+#else
+#define __nosanitizeaddress
+#endif
+
 /* Guard variables and structure members by lock. */
 #define __guarded_by(x)         __lock_annotate(guarded_by(x))
 #define __pt_guarded_by(x)      __lock_annotate(pt_guarded_by(x))
 
 #endif /* !_SYS_CDEFS_H_ */

head/sys/sys/linker_set.h

  * Private macros, not to be used outside this header file.
  */
 #ifdef __GNUCLIKE___SECTION
 #define __MAKE_SET_QV(set, sym, qv)                     \
         __GLOBL(__CONCAT(__start_set_,set));            \
         __GLOBL(__CONCAT(__stop_set_,set));             \
         static void const * qv                          \
         __set_##set##_sym_##sym __section("set_" #set)        \
+        __nosanitizeaddress                             \
         __used = &(sym)
 #define __MAKE_SET(set, sym)    __MAKE_SET_QV(set, sym, __MAKE_SET_CONST)
 #else /* !__GNUCLIKE___SECTION */
 #error this file needs to be ported to your compiler
 #endif /* __GNUCLIKE___SECTION */
 
 /*
  * Public macros.