[PATCH v5 01/22] elf: Avoid unnecessary slowdown from profiling with audit (BZ#15533)

[Florian Weimer]

* Adhemerval Zanella:

> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
> index 0d5b727c64..27f792b7b2 100644
> --- a/elf/dl-reloc.c
> +++ b/elf/dl-reloc.c
> @@ -203,11 +203,25 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>    const char *errstring = NULL;
>    int lazy = reloc_mode & RTLD_LAZY;
>    int skip_ifunc = reloc_mode & __RTLD_NOIFUNC;
> +  bool consider_symbind = false;

This needs __attribute__ ((unused)) or some fairly complex preprocessor
conditional.  Otherwise, the profiling builds performed by
build-many-glibcs.py fail.

>  #ifdef SHARED
>    /* If we are auditing, install the same handlers we need for profiling.  */
>    if ((reloc_mode & __RTLD_AUDIT) == 0)
> -    consider_profiling |= GLRO(dl_audit) != NULL;
> +    {
> +      struct audit_ifaces *afct = GLRO(dl_audit);
> +      for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
> +	{
> +	  /* Profiling is needed only if PLT hooks are provided.  */
> +	  if (afct->ARCH_LA_PLTENTER != NULL
> +	      || afct->ARCH_LA_PLTEXIT != NULL)
> +	    consider_profiling = 1;
> +	  if (afct->symbind != NULL)
> +	    consider_symbind = true;
> +
> +	  afct = afct->next;
> +	}
> +    }
>  #elif defined PROF
>    /* Never use dynamic linker profiling for gprof profiling code.  */
>  # define consider_profiling 0
> @@ -272,7 +286,7 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
>      ELF_DYNAMIC_RELOCATE (l, scope, lazy, consider_profiling, skip_ifunc);
>  
>  #ifndef PROF
> -    if (__glibc_unlikely (consider_profiling)
> +    if (consider_profiling | consider_symbind
>  	&& l->l_info[DT_PLTRELSZ] != NULL)
>        {
>  	/* Allocate the array which will contain the already found
> diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
> index 61c260ddb8..b0c788eb22 100644
> --- a/elf/dl-runtime.c
> +++ b/elf/dl-runtime.c
> @@ -44,6 +44,84 @@
>  # define ARCH_FIXUP_ATTRIBUTE
>  #endif
>  
> +#ifdef SHARED
> +static void
> +_dl_audit_symbind (struct link_map *l, struct reloc_result *reloc_result,
> +		   const ElfW(Sym) *defsym, DL_FIXUP_VALUE_TYPE *value,
> +		   lookup_t result)
> +{

Maybe start out with moving this function to elf/dl-audit.c (like it
happens later)?  It will make it easier to review the changes.

What are the actual function changes for _dl_audit_symbind?  The diff
isn't very readable even with diff -uw.

Thanks,
Florian