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Subject: Re: [PATCH v2 5/6] elf: Pass the fd to note processing
To:     Szabolcs Nagy <szabolcs.nagy@arm.com>, libc-alpha@sourceware.org
Cc:     Mark Rutland <mark.rutland@arm.com>,
        kernel-hardening@lists.openwall.com,
        Catalin Marinas <catalin.marinas@arm.com>,
        linux-kernel@vger.kernel.org,
        Jeremy Linton <jeremy.linton@arm.com>,
        Mark Brown <broonie@kernel.org>,
        Topi Miettinen <toiwoton@gmail.com>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org
References: <cover.1606319495.git.szabolcs.nagy@arm.com>
 <a23246987ec0a8b307a9a171193464b74a7cb416.1606319495.git.szabolcs.nagy@arm.com>
From:   Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Message-ID: <f181ee98-152a-7555-f883-b179e88aeadd@linaro.org>
Date:   Thu, 10 Dec 2020 15:35:10 -0300
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On 27/11/2020 10:21, Szabolcs Nagy via Libc-alpha wrote:
> To handle GNU property notes on aarch64 some segments need to
> be mmaped again, so the fd of the loaded ELF module is needed.
> 
> When the fd is not available (kernel loaded modules), then -1
> is passed.
> 
> The fd is passed to both _dl_process_pt_gnu_property and
> _dl_process_pt_note for consistency. Target specific note
> processing functions are updated accordingly.

LGTM, thanks.

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

> ---
>  elf/dl-load.c              | 12 +++++++-----
>  elf/rtld.c                 |  4 ++--
>  sysdeps/aarch64/dl-prop.h  |  6 +++---
>  sysdeps/generic/dl-prop.h  |  6 +++---
>  sysdeps/generic/ldsodefs.h |  5 +++--
>  sysdeps/x86/dl-prop.h      |  6 +++---
>  6 files changed, 21 insertions(+), 18 deletions(-)
> 
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index b0d65f32cc..74039f22a6 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -837,10 +837,12 @@ _dl_init_paths (const char *llp, const char *source)
>  
>  /* Process PT_GNU_PROPERTY program header PH in module L after
>     PT_LOAD segments are mapped.  Only one NT_GNU_PROPERTY_TYPE_0
> -   note is handled which contains processor specific properties.  */
> +   note is handled which contains processor specific properties.
> +   FD is -1 for the kernel mapped main executable otherwise it is
> +   the fd used for loading module L.  */
>  
>  void
> -_dl_process_pt_gnu_property (struct link_map *l, const ElfW(Phdr) *ph)
> +_dl_process_pt_gnu_property (struct link_map *l, int fd, const ElfW(Phdr) *ph)
>  {
>    const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
>    const ElfW(Addr) size = ph->p_memsz;

Ok.

> @@ -887,7 +889,7 @@ _dl_process_pt_gnu_property (struct link_map *l, const ElfW(Phdr) *ph)
>  	      last_type = type;
>  
>  	      /* Target specific property processing.  */
> -	      if (_dl_process_gnu_property (l, type, datasz, ptr) == 0)
> +	      if (_dl_process_gnu_property (l, fd, type, datasz, ptr) == 0)
>  		return;
>  
>  	      /* Check the next property item.  */

Ok.

> @@ -1379,10 +1381,10 @@ cannot enable executable stack as shared object requires");
>      switch (ph[-1].p_type)
>        {
>        case PT_NOTE:
> -	_dl_process_pt_note (l, &ph[-1]);
> +	_dl_process_pt_note (l, fd, &ph[-1]);
>  	break;
>        case PT_GNU_PROPERTY:
> -	_dl_process_pt_gnu_property (l, &ph[-1]);
> +	_dl_process_pt_gnu_property (l, fd, &ph[-1]);
>  	break;
>        }
>  

Ok.

> diff --git a/elf/rtld.c b/elf/rtld.c
> index c4ffc8d4b7..ec62567580 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -1540,10 +1540,10 @@ dl_main (const ElfW(Phdr) *phdr,
>      switch (ph[-1].p_type)
>        {
>        case PT_NOTE:
> -	_dl_process_pt_note (main_map, &ph[-1]);
> +	_dl_process_pt_note (main_map, -1, &ph[-1]);
>  	break;
>        case PT_GNU_PROPERTY:
> -	_dl_process_pt_gnu_property (main_map, &ph[-1]);
> +	_dl_process_pt_gnu_property (main_map, -1, &ph[-1]);
>  	break;
>        }
>  

Ok.

> diff --git a/sysdeps/aarch64/dl-prop.h b/sysdeps/aarch64/dl-prop.h
> index b0785bda83..2016d1472e 100644
> --- a/sysdeps/aarch64/dl-prop.h
> +++ b/sysdeps/aarch64/dl-prop.h
> @@ -35,13 +35,13 @@ _dl_open_check (struct link_map *m)
>  }
>  
>  static inline void __attribute__ ((always_inline))
> -_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph)
> +_dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
>  {
>  }
>  
>  static inline int
> -_dl_process_gnu_property (struct link_map *l, uint32_t type, uint32_t datasz,
> -			  void *data)
> +_dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
> +			  uint32_t datasz, void *data)
>  {
>    if (type == GNU_PROPERTY_AARCH64_FEATURE_1_AND)
>      {

Ok.

> diff --git a/sysdeps/generic/dl-prop.h b/sysdeps/generic/dl-prop.h
> index f1cf576fe3..df27ff8e6a 100644
> --- a/sysdeps/generic/dl-prop.h
> +++ b/sysdeps/generic/dl-prop.h
> @@ -37,15 +37,15 @@ _dl_open_check (struct link_map *m)
>  }
>  
>  static inline void __attribute__ ((always_inline))
> -_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph)
> +_dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
>  {
>  }
>  
>  /* Called for each property in the NT_GNU_PROPERTY_TYPE_0 note of L,
>     processing of the properties continues until this returns 0.  */
>  static inline int __attribute__ ((always_inline))
> -_dl_process_gnu_property (struct link_map *l, uint32_t type, uint32_t datasz,
> -			  void *data)
> +_dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
> +			  uint32_t datasz, void *data)
>  {
>    return 0;
>  }

Ok.

> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index b1da03cafe..89eab4719d 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -933,8 +933,9 @@ extern void _dl_rtld_di_serinfo (struct link_map *loader,
>  				 Dl_serinfo *si, bool counting);
>  
>  /* Process PT_GNU_PROPERTY program header PH in module L after
> -   PT_LOAD segments are mapped.  */
> -void _dl_process_pt_gnu_property (struct link_map *l, const ElfW(Phdr) *ph);
> +   PT_LOAD segments are mapped from file FD.  */
> +void _dl_process_pt_gnu_property (struct link_map *l, int fd,
> +				  const ElfW(Phdr) *ph);
>  
>  
>  /* Search loaded objects' symbol tables for a definition of the symbol

Ok.

> diff --git a/sysdeps/x86/dl-prop.h b/sysdeps/x86/dl-prop.h
> index 89911e19e2..4eb3b85a7b 100644
> --- a/sysdeps/x86/dl-prop.h
> +++ b/sysdeps/x86/dl-prop.h
> @@ -145,15 +145,15 @@ _dl_process_cet_property_note (struct link_map *l,
>  }
>  
>  static inline void __attribute__ ((unused))
> -_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph)
> +_dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
>  {
>    const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
>    _dl_process_cet_property_note (l, note, ph->p_memsz, ph->p_align);
>  }
>  
>  static inline int __attribute__ ((always_inline))
> -_dl_process_gnu_property (struct link_map *l, uint32_t type, uint32_t datasz,
> -			  void *data)
> +_dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
> +			  uint32_t datasz, void *data)
>  {
>    return 0;
>  }
> 

Ok.