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From: Florian Weimer <fw@deneb.enyo.de>
To: "Maciej W. Rozycki" <macro@mips.com>
Cc: <libc-alpha@sourceware.org>,  Alan Modra <amodra@gmail.com>
Subject: Re: [PATCH 1/2] elf: Accept absolute (SHN_ABS) symbols whose value is zero [BZ #23307]
References: <alpine.DEB.2.00.1806181533590.20622@tp.orcam.me.uk>
	<alpine.DEB.2.00.1806181716230.20622@tp.orcam.me.uk>
Date: Mon, 25 Jun 2018 20:25:00 -0000
In-Reply-To: <alpine.DEB.2.00.1806181716230.20622@tp.orcam.me.uk> (Maciej
	W. Rozycki's message of "Mon, 18 Jun 2018 19:07:03 +0100")
Message-ID: <87woum3977.fsf@mid.deneb.enyo.de>
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* Maciej W. Rozycki:

> --- glibc.orig/elf/dl-lookup.c	2018-06-17 09:06:30.202407070 +0100
> +++ glibc/elf/dl-lookup.c	2018-06-18 18:12:36.138114433 +0100
> @@ -76,6 +76,7 @@ check_match (const char *const undef_nam
>    unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
>    assert (ELF_RTYPE_CLASS_PLT == 1);
>    if (__glibc_unlikely ((sym->st_value == 0 /* No value.  */
> +			 && sym->st_shndx != SHN_ABS
>  			 && stt != STT_TLS)
>  			|| ELF_MACHINE_SYM_NO_MATCH (sym)
>  			|| (type_class & (sym->st_shndx == SHN_UNDEF))))

Context here:

  unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
  assert (ELF_RTYPE_CLASS_PLT == 1);
  if (__glibc_unlikely ((sym->st_value == 0 /* No value.  */
			 && stt != STT_TLS)
			|| ELF_MACHINE_SYM_NO_MATCH (sym)
			|| (type_class & (sym->st_shndx == SHN_UNDEF))))
    return NULL;

So this looks good.

> Index: glibc/elf/tst-absolute-zero-lib.c
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ glibc/elf/tst-absolute-zero-lib.c	2018-06-18 18:12:40.102324540 +0100
> @@ -0,0 +1,25 @@
> +/* BZ #xxxxx absolute zero symbol calculation shared module.

Needs Bugzilla number.

> Index: glibc/elf/tst-absolute-zero.c
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ glibc/elf/tst-absolute-zero.c	2018-06-18 18:12:40.147611912 +0100
> @@ -0,0 +1,38 @@
> +/* BZ #xxxxx absolute zero symbol calculation main executable.

Likewise.