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