lkml.org 
[lkml]   [2015]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 1/3] x86: Create and use a TOP_OF_KERNEL_STACK_PADDING macro
On Tue, Mar 10, 2015 at 8:22 PM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
> On 03/10/2015 07:05 PM, Andy Lutomirski wrote:
>> x86_32, unlike x86_64, pads the top of the kernel stack. Document
>> this padding and give it a name.
>>
>> This should make no change whatsoever to the compiled kernel image.
>> It also doesn't fix any of the current bugs in this area.
>>
>> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
>> ---
>> arch/x86/include/asm/processor.h | 3 ++-
>> arch/x86/include/asm/thread_info.h | 30 ++++++++++++++++++++++++++++++
>> 2 files changed, 32 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
>> index 48a61c1c626e..88d9aa745898 100644
>> --- a/arch/x86/include/asm/processor.h
>> +++ b/arch/x86/include/asm/processor.h
>> @@ -849,7 +849,8 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
>> #define task_pt_regs(task) \
>> ({ \
>> struct pt_regs *__regs__; \
>> - __regs__ = (struct pt_regs *)(KSTK_TOP(task_stack_page(task))-8); \
>> + __regs__ = (struct pt_regs *)(KSTK_TOP(task_stack_page(task)) - \
>> + TOP_OF_KERNEL_STACK_PADDING); \
>> __regs__ - 1; \
>> })

While we are at it, this macro can be simplified further. It uses KSTK_TOP,
and it's the only use of that macro. In turn, KSTK_TOP uses THREAD_SIZE_LONGS,
and it is the only use of that macro too!
(And to nitpick, this macro is whitespace-damaged. Seven space indent).

I'll send a patch based on your current git.


\
 
 \ /
  Last update: 2015-03-13 15:21    [W:0.193 / U:3.976 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site