[PATCH v2] lockdep: Fix static memory detection even more

Helge Deller
2023-08-14T22:32:09Z

On the parisc architecture, lockdep reports for all static objects which
are in the __initdata section (e.g. "setup_done" in devtmpfs,
"kthreadd_done" in init/main.c) this warning:

INFO: trying to register non-static key.

The warning itself is wrong, because those objects are in the __initdata
section, but the section itself is on parisc outside of range from
_stext to _end, which is why the static_obj() functions returns a wrong
answer.

While fixing this issue, I noticed that the whole existing check can
be simplified a lot.
Instead of checking against the _stext and _end symbols (which include
code areas too) just check for the .data and .bss segments (since we check a
data object). This can be done with the existing is_kernel_core_data()
macro.

In addition objects in the __initdata section can be checked with
init_section_contains(), and is_kernel_rodata() allows keys to be in the
_ro_after_init section.

This partly reverts and simplifies commit bac59d18c701 ("x86/setup: Fix static
memory detection").

Fixes: bac59d18c701 ("x86/setup: Fix static memory detection")
Signed-off-by: Helge Deller <deller@gmx.de>

---
v2:
- check is_kernel_rodata() as well, since keys are allowed in the
__ro_after_init section. Reported by kernel test robot.

---

diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index a6e8373a5170..3fa87e5e11ab 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -2,8 +2,6 @@
#ifndef _ASM_X86_SECTIONS_H
#define _ASM_X86_SECTIONS_H

-#define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
-
#include <asm-generic/sections.h>
#include <asm/extable.h>

@@ -18,20 +16,4 @@ extern char __end_of_kernel_reserve[];

extern unsigned long _brk_start, _brk_end;

-static inline bool arch_is_kernel_initmem_freed(unsigned long addr)
-{
- /*
- * If _brk_start has not been cleared, brk allocation is incomplete,
- * and we can not make assumptions about its use.
- */
- if (_brk_start)
- return 0;
-
- /*
- * After brk allocation is complete, space between _brk_end and _end
- * is available for allocation.
- */
- return addr >= _brk_end && addr < (unsigned long)&_end;
-}
-
#endif /* _ASM_X86_SECTIONS_H */
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 111607d91489..e85b5ad3e206 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -819,34 +819,26 @@ static int very_verbose(struct lock_class *class)
* Is this the address of a static object:
*/
#ifdef __KERNEL__
-/*
- * Check if an address is part of freed initmem. After initmem is freed,
- * memory can be allocated from it, and such allocations would then have
- * addresses within the range [_stext, _end].
- */
-#ifndef arch_is_kernel_initmem_freed
-static int arch_is_kernel_initmem_freed(unsigned long addr)
-{
- if (system_state < SYSTEM_FREEING_INITMEM)
- return 0;
-
- return init_section_contains((void *)addr, 1);
-}
-#endif
-
static int static_obj(const void *obj)
{
- unsigned long start = (unsigned long) &_stext,
- end = (unsigned long) &_end,
- addr = (unsigned long) obj;
+ unsigned long addr = (unsigned long) obj;

- if (arch_is_kernel_initmem_freed(addr))
- return 0;
+ if (is_kernel_core_data(addr))
+ return 1;
+
+ /*
+ * keys are allowed in the __ro_after_init section.
+ */
+ if (is_kernel_rodata(addr))
+ return 1;

/*
- * static variable?
+ * in initdata section and used during bootup only?
+ * NOTE: On some platforms the initdata section is
+ * outside of the _stext ... _end range.
*/
- if ((addr >= start) && (addr < end))
+ if (system_state < SYSTEM_FREEING_INITMEM &&
+ init_section_contains((void *)addr, 1))
return 1;

/*