lkml.org 
[lkml]   [2022]   [Mar]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: linux-next: build warnings after merge of the tip tree
On Tue, 22 Mar 2022 09:08:22 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Mar 22, 2022 at 02:31:36PM +0900, Masami Hiramatsu wrote:
>
> > > Also, I think both should fix regs->ss.
> >
> > I'm not sure this part. Since the return trampoline should run in the same
> > context of the called function, isn't ss same there too?
>
> It creates pt_regs on the stack, so the trampolines do:
>
> push $arch_rethook_trampoline
> push %rsp
> pushf
> sub $24, %rsp /* cs, ip, orig_ax */
> push %rdi
> ...
> push %r15
>
> That means that if anybody looks at regs->ss, it'll find
> $arch_rethook_trampoline, which isn't a valid segment descriptor, or am
> I just really bad at counting today?

Ah, got it. It seems that the ss was skipped from the beginning, and
no one argued that.

> I'm thinking you want a copy of __KERNEL_DS in that stack slot, not a
> function pointer.

The function pointer is for unwinding stack which involves the kretprobe.
Anyway, I can add a slot for ss if it is neeeded. But if it always be
__KERNEL_DS, is it worth to save it?

Thank you,


--
Masami Hiramatsu <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2022-03-22 10:15    [W:0.322 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site