On Wed, May 31, 2017 at 10:44 PM, Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > Some asm (and inline asm) code does special things to the stack which > objtool can't understand. (Nor can GCC or GNU assembler, for that > matter.) In such cases we need a facility for the code to provide > annotations, so the unwinder can unwind through it. > > This provides such a facility, in the form of CFI hints. They're > similar to the GNU assembler .cfi* directives, but they give more > information, and are needed in far fewer places, because objtool can > fill in the blanks by following branches and adjusting the stack pointer > for pushes and pops. Two minor suggestions: Could you prefix these with something other than "CFI_"? For those of use who have read the binutils manual, using "CFI_" sounds awfully like .cfi_, and people might expect the semantics to be the same. > +#define CFI_HINT(cfa_reg, cfa_offset, type) \ > + "999: \n\t" \ Have you checked if 999 is used elsewhere? My personal preference is to use: .Ldescriptive_text_\@: instead of a hopefully-unique number. I never researched the history, but I suspect that the convention of using large numbers came from early binutils versions that didn't have \@, but we use \@ fairly extensively in the kernel these days, so it would seem that we no longer support binutils versions that old. -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
