lkml.org 
[lkml]   [2017]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86
From
Date


On 11/17/17 9:25 AM, Oleg Nesterov wrote:
> On 11/15, Yonghong Song wrote:
>>
>> v3 -> v4:
>> . Revert most of v3 change as 32bit emulation is not really working
>> on x86_64 platform as among other issues, function emulate_push_stack()
>> needs to account for 32bit app on 64bit platform.
>> A separate effort is ongoing to address this issue.
>
> Reviewed-by: Oleg Nesterov <oleg@redhat.com>
>
>
>
> Please test your patch with the fix below, in this particular case the
> TIF_IA32 check should be fine. Although this is not what we really want,
> we should probably use user_64bit_mode(regs) which checks ->cs. But this
> needs more changes and doesn't solve other problems (get_unmapped_area)
> so I still can't decide what should we do right now...

I tested the below change with my patch. On x86_64, both 64bit and 32bit
program can be uprobe emulated properly. On x86_32, however, there is a
compilation error like below:

In function ‘check_copy_size’,
inlined from ‘copy_to_user’ at
/home/yhs/work/tip/include/linux/uaccess.h:154:6,
inlined from ‘emulate_push_stack.isra.9’ at
/home/yhs/work/tip/arch/x86/kernel/uprobes.c:535:6:
/home/yhs/work/tip/include/linux/thread_info.h:139:4: error: call to
‘__bad_copy_from’ declared with attribute error: copy source size is too
small
__bad_copy_from();

Basically, test_thread_flag(TIF_IA32) returns 0 on x86_32 system.

>
> Oleg.
>
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -516,7 +516,7 @@ struct uprobe_xol_ops {
>
> static inline int sizeof_long(void)
> {
> - return in_ia32_syscall() ? 4 : 8;
> + return test_thread_flag(TIF_IA32) ? 4 : 8;
> }
>
> static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
>

\
 
 \ /
  Last update: 2017-11-17 19:14    [W:0.051 / U:1.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site