Re: [PATCH 7/7] DWARF: add the config option

[Ingo Molnar]

* Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:

> > How are you handling control flow?
> 
> Control flow of what?
> 
> > > Here's the struct in its current state:
> > > 
> > > 	#define UNDWARF_REG_UNDEFINED		0
> > > 	#define UNDWARF_REG_CFA			1
> > > 	#define UNDWARF_REG_SP			2
> > > 	#define UNDWARF_REG_FP			3
> > > 	#define UNDWARF_REG_SP_INDIRECT		4
> > > 	#define UNDWARF_REG_FP_INDIRECT		5
> > > 	#define UNDWARF_REG_R10			6
> > > 	#define UNDWARF_REG_DI			7
> > > 	#define UNDWARF_REG_DX			8
> > > 
> > 
> > Why only those registers?  Also, if you have the option I would really
> > suggest using the actual x86 register numbers (ax, ex, dx, bx, sp, bp,
> > si, di, r8-r15 in that order.)
> 
> Those are the only registers which are ever needed as the base for
> finding the previous stack frame.  99% of the time it's sp or bp, the
> other registers are needed for aligned stacks and entry code.
> 
> Using the actual register numbers isn't an option because I don't need
> them all and they need to fit in a small number of bits.
> 
> This construct might be useful for other arches, which is why I called
> it "FP" instead of "BP".  But then I ruined that with the last 3 :-)

Please call it BP - 'FP' can easily be read as floating-point, making it all 
super-confusing. We should use canonical x86 register names and ordering - even
if not all registers are used straight away.

Thanks,

	Ingo