From bac59d18c7018a2fd5e800a1e72a8271bf404977 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@roeck-us.net>
Date: Thu, 30 Jan 2020 18:11:59 -0800
Subject: [PATCH] x86/setup: Fix static memory detection
When booting x86 images in qemu, the following warning is seen randomly
if DEBUG_LOCKDEP is enabled.
WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:1119
lockdep_register_key+0xc0/0x100
static_obj() returns true if an address is between _stext and _end.
On x86, this includes the brk memory space. Problem is that this memory
block is not static on x86; its unused portions are released after init
and can be allocated. This results in the observed warning if a lockdep
object is allocated from this memory.
Solve the problem by implementing arch_is_kernel_initmem_freed() for
x86 and have it return true if an address is within the released memory
range.
The same problem was solved for s390 with commit
7a5da02de8d6e ("locking/lockdep: check for freed initmem in static_obj()"),
which introduced arch_is_kernel_initmem_freed().
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200131021159.9178-1-linux@roeck-us.net
---
arch/x86/include/asm/sections.h | 20 ++++++++++++++++++++
arch/x86/kernel/setup.c | 1 -
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 036c360910c5d..a6e8373a5170f 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -2,6 +2,8 @@
#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>
@@ -14,4 +16,22 @@ extern char __end_rodata_hpage_align[];
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/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index a74262c714849..e6b545047f381 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -64,7 +64,6 @@ RESERVE_BRK(dmi_alloc, 65536);
* at link time, with RESERVE_BRK*() facility reserving additional
* chunks.
*/
-static __initdata
unsigned long _brk_start = (unsigned long)__brk_base;
unsigned long _brk_end = (unsigned long)__brk_base;
--
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