Re: [PATCH v2 dwarves 1/5] dwarves: help dwarf loader spot functions with optimized-out parameters

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Jan 30, 2023 at 05:10:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Jan 30, 2023 at 03:36:09PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > +#define NR_REGISTER_PARAMS	8
> > > +#elif defined(__arc__)
> > > +#define NR_REGISTER_PARAMS	8
> > > +#else
> > > +#define NR_REGISTER_PARAMS      0
> > > +#endif
> > 
> > This should be done as a function, something like:
> > 
> > int cu__nr_register_params(struct cu *cu)
> > {
> > 	GElf_Ehdr ehdr;
> > 
> > 	gelf_getehdr(cu->elf, &ehdr);
> > 
> > 	switch (ehdr.machine) {
> > 	...
> > 
> > }
> > 
> > I'm coding that now, will send the diff shortly.
> > 
> > This is to support cross-builds.
> 
> I made this change to this patch, please check.

And added this to that cset:

Committer notes:

Changed the NR_REGISTER_PARAMS definition from a if/elif/endif for the
native architecture into a function that uses the ELF header e_machine
to find the target architecture, to allow for cross builds. 

---

- Arnaldo

> diff --git a/dwarf_loader.c b/dwarf_loader.c
> index 752a3c1afc4494f2..81963e71715c8435 100644
> --- a/dwarf_loader.c
> +++ b/dwarf_loader.c
> @@ -994,29 +994,29 @@ static struct class_member *class_member__new(Dwarf_Die *die, struct cu *cu,
>  
>  /* How many function parameters are passed via registers?  Used below in
>   * determining if an argument has been optimized out or if it is simply
> - * an argument > NR_REGISTER_PARAMS.  Setting NR_REGISTER_PARAMS to 0
> - * allows unsupported architectures to skip tagging optimized-out
> + * an argument > cu__nr_register_params().  Making cu__nr_register_params()
> + * return 0 allows unsupported architectures to skip tagging optimized-out
>   * values.
>   */
> -#if defined(__x86_64__)
> -#define NR_REGISTER_PARAMS      6
> -#elif defined(__s390__)
> -#define NR_REGISTER_PARAMS	5
> -#elif defined(__aarch64__)
> -#define NR_REGISTER_PARAMS      8
> -#elif defined(__mips__)
> -#define NR_REGISTER_PARAMS	8
> -#elif defined(__powerpc__)
> -#define NR_REGISTER_PARAMS	8
> -#elif defined(__sparc__)
> -#define NR_REGISTER_PARAMS	6
> -#elif defined(__riscv) && __riscv_xlen == 64
> -#define NR_REGISTER_PARAMS	8
> -#elif defined(__arc__)
> -#define NR_REGISTER_PARAMS	8
> -#else
> -#define NR_REGISTER_PARAMS      0
> -#endif
> +static int arch__nr_register_params(const GElf_Ehdr *ehdr)
> +{
> +	switch (ehdr->e_machine) {
> +	case EM_S390:	 return 5;
> +	case EM_SPARC:
> +	case EM_SPARCV9:
> +	case EM_X86_64:	 return 6;
> +	case EM_AARCH64:
> +	case EM_ARC:
> +	case EM_ARM:
> +	case EM_MIPS:
> +	case EM_PPC:
> +	case EM_PPC64:
> +	case EM_RISCV:	 return 8;
> +	default:	 break;
> +	}
> +
> +	return 0;
> +}
>  
>  static struct parameter *parameter__new(Dwarf_Die *die, struct cu *cu,
>  					struct conf_load *conf, int param_idx)
> @@ -1031,7 +1031,7 @@ static struct parameter *parameter__new(Dwarf_Die *die, struct cu *cu,
>  		tag__init(&parm->tag, cu, die);
>  		parm->name = attr_string(die, DW_AT_name, conf);
>  
> -		if (param_idx >= NR_REGISTER_PARAMS)
> +		if (param_idx >= cu->nr_register_params)
>  			return parm;
>  		/* Parameters which use DW_AT_abstract_origin to point at
>  		 * the original parameter definition (with no name in the DIE)
> @@ -2870,6 +2870,7 @@ static int cu__set_common(struct cu *cu, struct conf_load *conf,
>  		return DWARF_CB_ABORT;
>  
>  	cu->little_endian = ehdr.e_ident[EI_DATA] == ELFDATA2LSB;
> +	cu->nr_register_params = arch__nr_register_params(&ehdr);
>  	return 0;
>  }
>  
> diff --git a/dwarves.h b/dwarves.h
> index fd1ca3ae9f4ab531..ddf56f0124e0ec03 100644
> --- a/dwarves.h
> +++ b/dwarves.h
> @@ -262,6 +262,7 @@ struct cu {
>  	uint8_t		 has_addr_info:1;
>  	uint8_t		 uses_global_strings:1;
>  	uint8_t		 little_endian:1;
> +	uint8_t		 nr_register_params;
>  	uint16_t	 language;
>  	unsigned long	 nr_inline_expansions;
>  	size_t		 size_inline_expansions;

-- 

- Arnaldo