Messages in this thread Patch in this message | | | From | Guenter Roeck <> | Subject | [PATCH] x86: Fix static memory detection | Date | Thu, 30 Jan 2020 18:11:59 -0800 |
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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> --- 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 036c360910c5..a6e8373a5170 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 1e4c20a1efec..08f5ceed70e0 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; -- 2.17.1
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