Re: [PATCH v2 1/2] dl-runtime: reloc_{offset,index} now functions arch overide'able

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 01/06/2020 19:18, Vineet Gupta wrote:
> The existing macros are fragile and expect local variables with a
> certain name. Fix this by defining them as functions with default
> implementation in a new header dl-runtime.h which arches can override
> if need be.
> 
> This came up during ARC port review, hence the need for argument pltgot
> in reloc_index() which is not needed by existing ports.
> 
> This patch potentially only affects hppa/x86 ports,
> build tested for both those configs and a few more.
> 
> Suggested-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

LGTM, thanks.  There are just style nits in the one-line comment
for new files.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

> ---
>  elf/dl-runtime.c            | 28 +++++++++++++++++-----------
>  elf/dl-runtime.h            | 30 ++++++++++++++++++++++++++++++
>  sysdeps/hppa/dl-runtime.c   |  4 ----
>  sysdeps/hppa/dl-runtime.h   | 31 +++++++++++++++++++++++++++++++
>  sysdeps/x86_64/dl-runtime.c |  9 ---------
>  sysdeps/x86_64/dl-runtime.h | 35 +++++++++++++++++++++++++++++++++++
>  6 files changed, 113 insertions(+), 24 deletions(-)
>  create mode 100644 elf/dl-runtime.h
>  create mode 100644 sysdeps/hppa/dl-runtime.h
>  delete mode 100644 sysdeps/x86_64/dl-runtime.c
>  create mode 100644 sysdeps/x86_64/dl-runtime.h
> 
> diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
> index cf5f1d3e82e1..85a229f6f019 100644
> --- a/elf/dl-runtime.c
> +++ b/elf/dl-runtime.c
> @@ -27,6 +27,7 @@
>  #include "dynamic-link.h"
>  #include <tls.h>
>  #include <dl-irel.h>
> +#include <dl-runtime.h>
>  
>  
>  #if (!ELF_MACHINE_NO_RELA && !defined ELF_MACHINE_PLT_REL) \
> @@ -42,13 +43,6 @@
>  # define ARCH_FIXUP_ATTRIBUTE
>  #endif
>  
> -#ifndef reloc_offset
> -# define reloc_offset reloc_arg
> -# define reloc_index  reloc_arg / sizeof (PLTREL)
> -#endif
> -
> -
> -
>  /* This function is called through a special trampoline from the PLT the
>     first time each PLT entry is called.  We must perform the relocation
>     specified in the PLT of the given shared object, and return the resolved
> @@ -68,8 +62,11 @@ _dl_fixup (
>      = (const void *) D_PTR (l, l_info[DT_SYMTAB]);
>    const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
>  
> +  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
> +
>    const PLTREL *const reloc
> -    = (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
> +    = (const void *) (D_PTR (l, l_info[DT_JMPREL])
> +		      + reloc_offset (pltgot, reloc_arg));
>    const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
>    const ElfW(Sym) *refsym = sym;
>    void *const rel_addr = (void *)(l->l_addr + reloc->r_offset);

Ok.

> @@ -180,9 +177,12 @@ _dl_profile_fixup (
>  			l, reloc_arg);
>      }
>  
> +  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
> +
>    /* This is the address in the array where we store the result of previous
>       relocations.  */
> -  struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
> +  struct reloc_result *reloc_result
> +    = &l->l_reloc_result[reloc_index (pltgot, reloc_arg, sizeof (PLTREL))];
>  
>   /* CONCURRENCY NOTES:
>  


Ok.
> @@ -219,8 +219,11 @@ _dl_profile_fixup (
>  	= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
>        const char *strtab = (const char *) D_PTR (l, l_info[DT_STRTAB]);
>  
> +      const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
> +
>        const PLTREL *const reloc
> -	= (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
> +	= (const void *) (D_PTR (l, l_info[DT_JMPREL])
> +			  + reloc_offset (pltgot, reloc_arg));
>        const ElfW(Sym) *refsym = &symtab[ELFW(R_SYM) (reloc->r_info)];
>        const ElfW(Sym) *defsym = refsym;
>        lookup_t result;

Ok.

> @@ -485,11 +488,14 @@ _dl_call_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
>  		  const void *inregs, void *outregs)
>  {
>  #ifdef SHARED
> +  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
> +
>    /* This is the address in the array where we store the result of previous
>       relocations.  */
>    // XXX Maybe the bound information must be stored on the stack since
>    // XXX with bind_not a new value could have been stored in the meantime.
> -  struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
> +  struct reloc_result *reloc_result =
> +    &l->l_reloc_result[reloc_index (pltgot, reloc_arg, sizeof (PLTREL))];
>    ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
>  					    l_info[DT_SYMTAB])
>  		       + reloc_result->boundndx);

Ok.

> diff --git a/elf/dl-runtime.h b/elf/dl-runtime.h
> new file mode 100644
> index 000000000000..dd87d799465e
> --- /dev/null
> +++ b/elf/dl-runtime.h
> @@ -0,0 +1,30 @@
> +/* Helpers for On-demand PLT fixup for shared objects. Generic version.

Double space after period.

> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, write to the Free
> +   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> +   02111-1307 USA.  */
> +
> +static inline uintptr_t
> +reloc_offset (uintptr_t plt0, uintptr_t pltn)
> +{
> +  return pltn;
> +}
> +
> +static inline uintptr_t
> +reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
> +{
> +  return pltn / size;
> +}

Ok.

> diff --git a/sysdeps/hppa/dl-runtime.c b/sysdeps/hppa/dl-runtime.c
> index 885a3f1837cb..2d061b150f06 100644
> --- a/sysdeps/hppa/dl-runtime.c
> +++ b/sysdeps/hppa/dl-runtime.c
> @@ -17,10 +17,6 @@
>     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
>     02111-1307 USA.  */
>  
> -/* Clear PA_GP_RELOC bit in relocation offset.  */
> -#define reloc_offset (reloc_arg & ~PA_GP_RELOC)
> -#define reloc_index  (reloc_arg & ~PA_GP_RELOC) / sizeof (PLTREL)
> -
>  #include <elf/dl-runtime.c>
>  
>  /* The caller has encountered a partially relocated function descriptor.

Ok.

> diff --git a/sysdeps/hppa/dl-runtime.h b/sysdeps/hppa/dl-runtime.h
> new file mode 100644
> index 000000000000..be3bc929c74c
> --- /dev/null
> +++ b/sysdeps/hppa/dl-runtime.h
> @@ -0,0 +1,31 @@
> +/* Helpers for On-demand PLT fixup for shared objects. HPAA version.

Double space after period.

> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, write to the Free
> +   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> +   02111-1307 USA.  */
> +
> +/* Clear PA_GP_RELOC bit in relocation offset.  */
> +static inline uintptr_t
> +reloc_offset (uintptr_t plt0, uintptr_t pltn)
> +{
> +  return pltn & ~PA_GP_RELOC;
> +}
> +
> +static inline uintptr_t
> +reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
> +{
> +  return (pltn & ~PA_GP_RELOC )/ size;
> +}

Ok,

> diff --git a/sysdeps/x86_64/dl-runtime.c b/sysdeps/x86_64/dl-runtime.c
> deleted file mode 100644
> index b625d1e88257..000000000000
> --- a/sysdeps/x86_64/dl-runtime.c
> +++ /dev/null
> @@ -1,9 +0,0 @@
> -/* The ABI calls for the PLT stubs to pass the index of the relocation
> -   and not its offset.  In _dl_profile_fixup and _dl_call_pltexit we
> -   also use the index.  Therefore it is wasteful to compute the offset
> -   in the trampoline just to reverse the operation immediately
> -   afterwards.  */
> -#define reloc_offset reloc_arg * sizeof (PLTREL)
> -#define reloc_index  reloc_arg
> -
> -#include <elf/dl-runtime.c>

Ok.

> diff --git a/sysdeps/x86_64/dl-runtime.h b/sysdeps/x86_64/dl-runtime.h
> new file mode 100644
> index 000000000000..b82fdce8367d
> --- /dev/null
> +++ b/sysdeps/x86_64/dl-runtime.h
> @@ -0,0 +1,35 @@
> +/* Helpers for On-demand PLT fixup for shared objects. x86_64 version.

Double space after period.

> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, write to the Free
> +   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> +   02111-1307 USA.  */
> +
> +/* The ABI calls for the PLT stubs to pass the index of the relocation
> +   and not its offset.  In _dl_profile_fixup and _dl_call_pltexit we
> +   also use the index.  Therefore it is wasteful to compute the offset
> +   in the trampoline just to reverse the operation immediately
> +   afterwards.  */
> +static inline uintptr_t
> +reloc_offset (uintptr_t plt0, uintptr_t pltn)
> +{
> +  return pltn * sizeof (ElfW(Rela));
> +}
> +
> +static inline uintptr_t
> +reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
> +{
> +  return pltn;
> +}
> 

Ok.

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