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    SubjectRe: [PATCH v4 10/17] x86/entry/64: Really create an error-entry-from-usermode code path
    On Mon, Jun 29, 2015 at 12:33:42PM -0700, Andy Lutomirski wrote:
    > In 539f51136500 ("x86/asm/entry/64: Disentangle error_entry/exit
    > gsbase/ebx/usermode code"), I arranged the code slightly wrong --
    > IRET faults would skip the code path that was intended to execute on
    > all error entries from user mode. Fix it up.
    >
    > This does not fix a bug, but we'll need it, and it slightly shrinks
    > the code.
    >
    > Signed-off-by: Andy Lutomirski <luto@kernel.org>
    > ---
    > arch/x86/entry/entry_64.S | 12 ++++++++----
    > 1 file changed, 8 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    > index 141a5d49dddc..cd9cbc62159c 100644
    > --- a/arch/x86/entry/entry_64.S
    > +++ b/arch/x86/entry/entry_64.S
    > @@ -1145,9 +1145,14 @@ ENTRY(error_entry)
    > testb $3, CS+8(%rsp)
    > jz error_kernelspace
    >
    > - /* We entered from user mode */
    > +error_entry_from_usermode_swapgs:
    > + /*
    > + * We entered from user mode or we're pretending to have entered
    > + * from user mode due to an IRET fault.
    > + */
    > SWAPGS
    >
    > +error_entry_from_usermode_after_swapgs:
    > error_entry_done:

    Why the second label?

    Also, please make all those labels local by prefixing them with .L
    because they appear unnecesasrily in objdump output as global symbols.

    $ objdump -d vmlinux | grep -E "^[0-9a-f]+ <(error_entry_\w*|error_kernelspace|bstep_iret|error_bad_iret)"
    ffffffff8167a4a8 <error_entry_from_usermode_swapgs>:
    ffffffff8167a4ab <error_entry_done>:
    ffffffff8167a4b1 <error_kernelspace>:
    ffffffff8167a4e0 <bstep_iret>:
    ffffffff8167a4e8 <error_bad_iret>:

    Oh, and shorter please :)

    --
    Regards/Gruss,
    Boris.

    ECO tip #101: Trim your mails when you reply.
    --


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