On Thu, Jan 08, 2015 at 05:25:14PM +0100, Denys Vlasenko wrote:
> This is a preparatory patch for change in "struct pt_regs"
> handling in entry_64.S.
>
> trace_hardirqs thunks were (ab)using a part of pt_regs
> handling code, namely SAVE_ARGS/RESTORE_ARGS macros,
> to save/restore registers across C function calls.
>
> Since SAVE_ARGS is going to be changed, open-code
> register saving/restoring here.
>
> Incidentally, this removes a bit of dead code:
> one SAVE_ARGS was used just to emit a CFI annotation,
> but it also generated unreachable assembly insns.
>
> Signed-off-by: Denys Vlasenko <[email protected]>
> CC: Linus Torvalds <[email protected]>
> CC: Oleg Nesterov <[email protected]>
> CC: "H. Peter Anvin" <[email protected]>
> CC: Andy Lutomirski <[email protected]>
> CC: Frederic Weisbecker <[email protected]>
> CC: X86 ML <[email protected]>
> CC: Alexei Starovoitov <[email protected]>
> CC: Will Drewry <[email protected]>
> CC: Kees Cook <[email protected]>
> CC: [email protected]
> ---
> arch/x86/lib/thunk_64.S | 29 ++++++++++++++++++++++++-----
> 1 file changed, 24 insertions(+), 5 deletions(-)
Hmm, this patch breaks booting my kvm guest: it stops booting at some
point and restarts itself after a couple of seconds.
The monitor says rIP points to ffffffff8167ae30 which is this:
ffffffff8167ae30 <async_page_fault>:
ffffffff8167ae30: ff 15 fa 62 31 00 callq *0x3162fa(%rip) #
ffffffff81991130 <pv_irq_ops+0x30>
ffffffff8167ae36: 48 83 ec 78 sub $0x78,%rsp
ffffffff8167ae3a: e8 d1 01 00 00 callq ffffffff8167b010
<error_entry>
ffffffff8167ae3f: 48 89 e7 mov %rsp,%rdi
ffffffff8167ae42: 48 8b 74 24 78 mov 0x78(%rsp),%rsi
ffffffff8167ae47: 48 c7 44 24 78 ff ff movq
$0xffffffffffffffff,0x78(%rsp)
ffffffff8167ae4e: ff ff
ffffffff8167ae50: e8 9b 9e 9c ff callq ffffffff81044cf0
<do_async_page_fault>
ffffffff8167ae55: e9 76 02 00 00 jmpq ffffffff8167b0d0
<error_exit>
ffffffff8167ae5a: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
HTH.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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