.cfi指令解读（二）
转自：http://sourceware.org/binutils/docs/as/CFI-directives.html
先看吧，时间太紧了没时间翻译。等什么时候有时间再说吧。
7.11 .cfi_sections section_list
.cfi_sections may be used to specify whether CFI directives should emit .eh_frame section and/or .debug_frame section. If section_list is .eh_frame, .eh_frame is emitted, if section_list is .debug_frame, .debug_frame is emitted. To emit both use .eh_frame, .debug_frame. The default if this directive is not used is .cfi_sections .eh_frame.
7.12 .cfi_startproc [simple]
.cfi_startproc is used at the beginning of each function that should have an entry in .eh_frame. It initializes some internal data structures. Don't forget to close the function by .cfi_endproc.
Unless .cfi_startproc is used along with parameter simple it also emits some architecture dependent initial CFI instructions.
7.13 .cfi_endproc
.cfi_endproc is used at the end of a function where it closes its unwind entry previously opened by .cfi_startproc, and emits it to .eh_frame.
7.14 .cfi_personality encoding [, exp]
.cfi_personality defines personality routine and its encoding. encoding must be a constant determining how the personality should be encoded. If it is 255 (DW_EH_PE_omit), second argument is not present, otherwise second argument should be a constant or a symbol name. When using indirect encodings, the symbol provided should be the location where personality can be loaded from, not the personality routine itself. The default after .cfi_startproc is .cfi_personality 0xff, no personality routine.
7.15 .cfi_lsda encoding [, exp]
.cfi_lsda defines LSDA and its encoding. encoding must be a constant determining how the LSDA should be encoded. If it is 255 (DW_EH_PE_omit), second argument is not present, otherwise second argument should be a constant or a symbol name. The default after .cfi_startproc is .cfi_lsda 0xff, no LSDA.
7.16 .cfi_def_cfa register, offset
.cfi_def_cfa defines a rule for computing CFA as: take address from register and add offset to it.
7.17 .cfi_def_cfa_register register
.cfi_def_cfa_register modifies a rule for computing CFA. From now on register will be used instead of the old one. Offset remains the same.
7.18 .cfi_def_cfa_offset offset
.cfi_def_cfa_offset modifies a rule for computing CFA. Register remains the same, but offset is new. Note that it is the absolute offset that will be added to a defined register to compute CFA address.
7.19 .cfi_adjust_cfa_offset offset
Same as .cfi_def_cfa_offset but offset is a relative value that is added/substracted from the previous offset.
7.20 .cfi_offset register, offset
Previous value of register is saved at offset offset from CFA.
7.21 .cfi_rel_offset register, offset
Previous value of register is saved at offset offset from the current CFA register. This is transformed to .cfi_offset using the known displacement of the CFA register from the CFA. This is often easier to use, because the number will match the code it's annotating.
7.22 .cfi_register register1, register2
Previous value of register1 is saved in register register2.
7.23 .cfi_restore register
.cfi_restore says that the rule for register is now the same as it was at the beginning of the function, after all initial instruction added by .cfi_startproc were executed.
7.24 .cfi_undefined register
From now on the previous value of register can't be restored anymore.
7.25 .cfi_same_value register
Current value of register is the same like in the previous frame, i.e. no restoration needed.
7.26 .cfi_remember_state,
First save all current rules for all registers by .cfi_remember_state, then totally screw them up by subsequent .cfi_* directives and when everything is hopelessly bad, use .cfi_restore_state to restore the previous saved state.
7.27 .cfi_return_column register
Change return column register, i.e. the return address is either directly in register or can be accessed by rules for register.
7.28 .cfi_signal_frame
Mark current function as signal trampoline.
7.29 .cfi_window_save
SPARC register window has been saved.
7.30 .cfi_escape expression[, ...]
Allows the user to add arbitrary bytes to the unwind info. One might use this to add OS-specific CFI opcodes, or generic CFI opcodes that GAS does not yet support.
7.31 .cfi_val_encoded_addr register, encoding, label
The current value of register is label. The value of label will be encoded in the output file according to encoding; see the description of .cfi_personality for details on this encoding.
The usefulness of equating a register to a fixed label is probably limited to the return address register. Here, it can be useful to mark a code segment that has only one return address which is reached by a direct branch and no copy of the return address exists in memory or another register.