[PATCH] lockdep: Fix static memory detection even more

* [PATCH] lockdep: Fix static memory detection even more
@ 2023-08-12 15:48 Helge Deller
  2023-08-14 13:40 ` kernel test robot
  2023-09-03 19:36 ` Guenter Roeck
  0 siblings, 2 replies; 13+ messages in thread
From: Helge Deller @ 2023-08-12 15:48 UTC (permalink / raw)
  To: Andrew Morton, Greg Kroah-Hartman, Rafael J. Wysocki,
	linux-kernel, linux-parisc, Guenter Roeck, Borislav Petkov,
	Peter Zijlstra

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().

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

Tested on x86-64 and parisc.

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

---

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..957b785d0b59 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -819,34 +819,20 @@ 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;

 	/*
-	 * 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;

 	/*

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