Re: [PATCH 3/4] elf: Generalize name-based DSO recognition in ldconfig

[Carlos O'Donell <carlos@redhat.com>]

On 6/10/21 4:23 AM, Florian Weimer via Libc-alpha wrote:
> This introduces <dl-is_dso.h> and the _dl_is_dso function.  A
> test ensures that the official names of libc.so, ld.so, and their
> versioned names are recognized.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  elf/Makefile        |  2 +-
>  elf/dl-is_dso.h     | 33 +++++++++++++++++++++++++++++++++
>  elf/ldconfig.c      |  5 ++---
>  elf/tst-dl-is_dso.c | 35 +++++++++++++++++++++++++++++++++++
>  4 files changed, 71 insertions(+), 4 deletions(-)
>  create mode 100644 elf/dl-is_dso.h
>  create mode 100644 elf/tst-dl-is_dso.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 5c47daee12..1751f5ec67 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -223,7 +223,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>  	 tst-single_threaded tst-single_threaded-pthread \
>  	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
>  	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> -	 tst-tls20 tst-tls21 tst-dlmopen-dlerror
> +	 tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dl-is_dso

OK.

>  #	 reldep9
>  tests-internal += loadtest unload unload2 circleload1 \
>  	 neededtest neededtest2 neededtest3 neededtest4 \
> diff --git a/elf/dl-is_dso.h b/elf/dl-is_dso.h
> new file mode 100644
> index 0000000000..94e00966a1
> --- /dev/null
> +++ b/elf/dl-is_dso.h
> @@ -0,0 +1,33 @@
> +/* Heuristic for recognizing DSO file names.
> +   Copyright (C) 2021 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, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdbool.h>
> +#include <string.h>
> +
> +/* Returns true if the file name looks like a DSO name.  */
> +static bool
> +_dl_is_dso (const char *name)
> +{
> +  /* Recognize lib*.so*, ld-*.so*, ld.so.*, ld64.so.*.  ld-*.so*
> +     matches both platform dynamic linker names like ld-linux.so.2,
> +     and versioned dynamic loader names like ld-2.12.so.  */
> +  return (((strncmp (name, "lib", 3) == 0 || strncmp (name, "ld-", 3) == 0)
> +           && strstr (name, ".so") != NULL)
> +          || strncmp (name, "ld.so.", 6) == 0
> +          || strncmp (name, "ld64.so.", 8) == 0);

OK. Refactor and change. This expands the definition a bit, but it should
still be correct to capture the wider set of names.

> +}
> diff --git a/elf/ldconfig.c b/elf/ldconfig.c
> index 96bf7700b2..1037e8d0cf 100644
> --- a/elf/ldconfig.c
> +++ b/elf/ldconfig.c
> @@ -43,6 +43,7 @@
>  #include <ldconfig.h>
>  #include <dl-cache.h>
>  #include <dl-hwcaps.h>
> +#include <dl-is_dso.h>

OK.

>  
>  #include <dl-procinfo.h>
>  
> @@ -842,9 +843,7 @@ search_dir (const struct dir_entry *entry)
>  	 subdirectory (if not already processing a glibc-hwcaps
>  	 subdirectory)?  The dynamic linker is also considered as
>  	 shared library.  */
> -      if (((strncmp (direntry->d_name, "lib", 3) != 0
> -	    && strncmp (direntry->d_name, "ld-", 3) != 0)
> -	   || strstr (direntry->d_name, ".so") == NULL)
> +      if (!_dl_is_dso (direntry->d_name)

OK.

>  	  && (direntry->d_type == DT_REG
>  	      || (entry->hwcaps == NULL
>  		  && !is_hwcap_platform (direntry->d_name))))
> diff --git a/elf/tst-dl-is_dso.c b/elf/tst-dl-is_dso.c
> new file mode 100644
> index 0000000000..48d2cc9fbe
> --- /dev/null
> +++ b/elf/tst-dl-is_dso.c
> @@ -0,0 +1,35 @@
> +/* Test heuristic for recognizing DSO file names.
> +   Copyright (C) 2021 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, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <dl-is_dso.h>
> +#include <gnu/lib-names.h>
> +#include <support/check.h>
> +
> +static int
> +do_test (void)
> +{
> +  /* Official ABI names.  */
> +  TEST_VERIFY (_dl_is_dso (LIBC_SO));
> +  TEST_VERIFY (_dl_is_dso (LD_SO));

OK.

> +  /* Version-based names.  The version number does not matter.  */
> +  TEST_VERIFY (_dl_is_dso ("libc-2.12.so"));
> +  TEST_VERIFY (_dl_is_dso ("ld-2.12.so"));

OK.

> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> 


-- 
Cheers,
Carlos.