[lkml]   [2017]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] x86/selftests: add clobbers for int80 on x86_64
On 02/10/2017 07:13 PM, Andy Lutomirski wrote:
> On Fri, Feb 10, 2017 at 3:52 AM, Dmitry Safonov <> wrote:
>> Kernel erases R8..R11 registers prior returning to userspace
>> from int80:
>> GCC can reuse this registers and doesn't expect them to change
>> during syscall invocation. I met this kind of bug in CRIU once
>> gcc 6.1 and clang stored local variables in those registers
>> and the kernel zerofied them during syscall:
>> By that reason I suggest to add those registers to clobbers
>> in selftests.
> Seems reasonable, but presumably INT80_CLOBBERS should be defined the
> same way in all the tests. IOW, if the "flags" clobber is actually
> needed, it should be "flags", INT80_CLOBBERS (possibly without the
> comma if it's problematic).

Well, that was my initial attempt: I've defined it as:
+# define INT80_CLOBBERS , "r8", "r9", "r10", "r11"

But that hanging comma looks awful, so I added "flags" there.
And if I do define it without coma and leave it in asm statement,
32-bit version would be unhappy.
So, I found that it's easier to define it with flags included.


 \ /
  Last update: 2017-02-10 17:51    [W:0.045 / U:2.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site