linux-kernel - [PATCH v3 2/4] mm: Make generic arch_is_kernel_initmem

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Message-Id: <1d40783e676e07858be97d881f449ee7ea8adfb1.1633001016.git.christophe.leroy@csgroup.eu>
Date:   Thu, 30 Sep 2021 13:23:44 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Andrew Morton <akpm@...ux-foundation.org>, arnd@...db.de
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arch@...r.kernel.org,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: [PATCH v3 2/4] mm: Make generic arch_is_kernel_initmem_freed() do what it says

Commit 7a5da02de8d6 ("locking/lockdep: check for freed initmem in
static_obj()") added arch_is_kernel_initmem_freed() which is supposed
to report whether an object is part of already freed init memory.

For the time being, the generic version of arch_is_kernel_initmem_freed()
always reports 'false', allthough free_initmem() is generically called
on all architectures.

Therefore, change the generic version of arch_is_kernel_initmem_freed()
to check whether free_initmem() has been called. If so, then check
if a given address falls into init memory.

To ease the use of system_state, move it out of line into its only
caller which is lockdep.c

Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v3: Move it out of sections.h into lockdep.c and fix the comment.

v2: Change to using the new SYSTEM_FREEING_INITMEM state
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 include/asm-generic/sections.h | 14 --------------
 kernel/locking/lockdep.c       | 15 +++++++++++++++
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d16302d3eb59..596ab2092289 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -80,20 +80,6 @@ static inline int arch_is_kernel_data(unsigned long addr)
 }
 #endif
 
-/*
- * Check if an address is part of freed initmem. This is needed on architectures
- * with virt == phys kernel mapping, for code that wants to check if an address
- * is part of a static object within [_stext, _end]. 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 inline int arch_is_kernel_initmem_freed(unsigned long addr)
-{
-	return 0;
-}
-#endif
-
 /**
  * memory_contains - checks if an object is contained within a memory region
  * @begin: virtual address of the beginning of the memory region
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index bf1c00c881e4..8e118caf835e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -788,6 +788,21 @@ 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,
-- 
2.31.1