lkml.org 
[lkml]   [2020]   [Mar]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: Fix static memory detection
ping ... I still see this problem.

Guenter

On Thu, Jan 30, 2020 at 06:11:59PM -0800, Guenter Roeck wrote:
> 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;
>

\
 
 \ /
  Last update: 2020-03-17 14:45    [W:0.041 / U:1.764 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site