Re: [PATCH 4/5] x86: entry_64.S: always allocate complete "struct pt_regs"

[Denys Vlasenko]

On 08/11/2014 10:40 AM, Jan Beulich wrote:
>>>>>       CFI_ESCAPE      0x0f /* DW_CFA_def_cfa_expression */, 6, \
>>>>>                       0x77 /* DW_OP_breg7 */, 0, \
>>>>>                       0x06 /* DW_OP_deref */, \
>>>>> -                     0x08 /* DW_OP_const1u */, SS+8-RBP, \
>>>>> +                     0x08 /* DW_OP_const1u */, SS+8, \
>>>>>                       0x22 /* DW_OP_plus */
>>>>>       /* We entered an interrupt context - irqs are off: */
>>>>>       TRACE_IRQS_OFF
...
...
>>> While we are at it, what this  CFI_ESCAPE thing does here?
>>> As usual, it has no comment :/
> 
> Each of its lines has a comment; with other CFI annotations not
> each having comments, I don't see what else is needed here.

The existing comments explain what every byte means.
They are useful if CFI-literate reader wants to check correctness
of the encoding of this annotation.

There is no overall comment what this CFI annotation
*achieves*. In human language, what do we say
to DWARF decoder here?

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