Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-07-11 Thread Ingo Molnar
* Josh Poimboeuf wrote: > Anyway, I used some linker magic to temporarily move the unwinder code to the > end of .text, so that unwinder changes don't add unexpected side effects to > the > microbenchmark behavior. Now I'm getting more consistent results: the packed > struct is measuring ~2

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-07-10 Thread Josh Poimboeuf
On Fri, Jul 07, 2017 at 11:44:37AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf wrote: > > > On Thu, Jun 29, 2017 at 10:06:52AM -0500, Josh Poimboeuf wrote: > > > On Thu, Jun 29, 2017 at 04:46:18PM +0200, Ingo Molnar wrote: > > > > > > > > * Josh Poimboeuf wrote: > > > > > > > > > > Plus, s

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-07-07 Thread Ingo Molnar
* Josh Poimboeuf wrote: > On Thu, Jun 29, 2017 at 10:06:52AM -0500, Josh Poimboeuf wrote: > > On Thu, Jun 29, 2017 at 04:46:18PM +0200, Ingo Molnar wrote: > > > > > > * Josh Poimboeuf wrote: > > > > > > > > Plus, shouldn't we use __packed for 'struct undwarf' to minimize the > > > > > struct

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-07-06 Thread Josh Poimboeuf
On Thu, Jun 29, 2017 at 10:06:52AM -0500, Josh Poimboeuf wrote: > On Thu, Jun 29, 2017 at 04:46:18PM +0200, Ingo Molnar wrote: > > > > * Josh Poimboeuf wrote: > > > > > > Plus, shouldn't we use __packed for 'struct undwarf' to minimize the > > > > structure's size (to 6 bytes AFAICS?) - or is o

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Josh Poimboeuf
On Thu, Jun 29, 2017 at 04:46:18PM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf wrote: > > > > Plus, shouldn't we use __packed for 'struct undwarf' to minimize the > > > structure's size (to 6 bytes AFAICS?) - or is optimal packing of the main > > > undwarf array already guaranteed on every

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Ingo Molnar
* Josh Poimboeuf wrote: > > Plus, shouldn't we use __packed for 'struct undwarf' to minimize the > > structure's size (to 6 bytes AFAICS?) - or is optimal packing of the main > > undwarf array already guaranteed on every platform with this layout? > > Ah yes, it should definitely be packed (a

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Josh Poimboeuf
On Thu, Jun 29, 2017 at 09:25:12AM +0200, Ingo Molnar wrote: > > +/* > > + * This struct contains a simplified version of the DWARF Call Frame > > + * Information standard. It contains only the necessary parts of the real > > + * DWARF, simplified for ease of access by the in-kernel unwinder. It

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Josh Poimboeuf
On Thu, Jun 29, 2017 at 09:14:14AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf wrote: > > > Now that objtool knows the states of all registers on the stack for each > > instruction, it's straightforward to generate debuginfo for an unwinder > > to use. > > > > Instead of generating DWARF, ge

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Ingo Molnar
* Josh Poimboeuf wrote: > +#ifndef _UNDWARF_TYPES_H > +#define _UNDWARF_TYPES_H > + > +/* > + * The UNDWARF_REG_* registers are base registers which are used to find > other > + * registers on the stack. > + * > + * The CFA (call frame address) is the value of the stack pointer on the > + * pre

Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation

2017-06-29 Thread Ingo Molnar
* Josh Poimboeuf wrote: > Now that objtool knows the states of all registers on the stack for each > instruction, it's straightforward to generate debuginfo for an unwinder > to use. > > Instead of generating DWARF, generate a new format called undwarf, which > is more suitable for an in-kernel