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Bug#1028200: marked as done (glibc: FTBFS on alpha due to buggy GL(dl_phdr) and GL(dl_phnum) [BZ #29864])

Your message dated Tue, 16 May 2023 19:50:11 +0000
with message-id <E1pz0gV-00DW3d-Jz@fasolo.debian.org>
and subject line Bug#1028200: fixed in glibc 2.37-1
has caused the Debian Bug report #1028200,
regarding glibc: FTBFS on alpha due to buggy GL(dl_phdr) and GL(dl_phnum) [BZ #29864]
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
1028200: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1028200
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Source: glibc
Version: 2.36-8
Severity: normal
Tags: patch upstream
User: debian-alpha@lists.debian.org
Usertags: alpha
X-Debbugs-Cc: debian-alpha@lists.debian.org

Hello!

glibc fails to build from source on alpha with many testsuite failures [1]
due to a regression introduced in glibc 2.34 [2].

According to the discussion on the libc-alpha mailing list, this issue
affects multiple architectures for static builds. It just happens that
it causes segmentation faults on alpha [3].

A proposed patch by Adhemveral Zanella has been posted on the list [4]
but not been merged yet. I tested the first version of the patch [3] and
can confirm that it works. I will test the posted version [4] now.

Adhemerval said that he plans to backport the patch down to 2.34, so it
will eventually show up in 2.36 as well. Either way, it might be a good
idea to already carry the patch in Debian but I'm not sure.

Thanks,
Adrian

> [1] https://buildd.debian.org/status/logs.php?pkg=glibc&arch=alpha
> [2] https://sourceware.org/pipermail/libc-alpha/2023-January/144445.html
> [3] https://sourceware.org/pipermail/libc-alpha/2023-January/144452.html
> [4] https://sourceware.org/pipermail/libc-alpha/2023-January/144457.html

--
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
--- Begin Message --- 
The 73fc4e28b9464f0e refactor did not add the GL(dl_phdr) and
GL(dl_phnum) for static build, relying on the __ehdr_start symbol,
which is always added by the static linker, to get the correct values.

This is problematic in some ways:

  - The segment may see its in-memory size differ from its in-file
    size (or the binary may have holes).  The Linux has fixed is to
    provide concise values for both AT_PHDR and AT_PHNUM (commit
    0da1d5002745c - "fs/binfmt_elf: Fix AT_PHDR for unusual ELF files")

  - Some archs (alpha for instance) the hidden weak reference is not
    correctly pulled by the static linker and  __ehdr_start address
    end up being 0, which makes GL(dl_phdr) and GL(dl_phnum) have both
    invalid values (and triggering a segfault later on libc.so while
    accessing TLS variables).

The safer fix is to just restore the previous behavior to setup
GL(dl_phdr) and GL(dl_phnum) for static based on kernel auxv.  The
__ehdr_start fallback can also be simplified by not assuming weak
linkage (as for PIE).

The libc-static.c auxv init logic is moved to dl-support.c, since
the later is build without SHARED and then GLRO macro is defined
to access the variables directly.

The _dl_phdr is also assumed to be always non NULL, since an invalid
NULL values does not trigger TLS initialization (which is used in
various libc systems).

Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
---
 csu/libc-start.c                        | 21 ----------
 csu/libc-tls.c                          | 25 ++++++------
 elf/dl-support.c                        | 52 ++++++++++++++++---------
 sysdeps/unix/sysv/linux/dl-parse_auxv.h |  1 +
 4 files changed, 46 insertions(+), 53 deletions(-)

diff --git a/csu/libc-start.c b/csu/libc-start.c
index 543560f36c..bfeee6d851 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -262,28 +262,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   }
 #  endif
   _dl_aux_init (auxvec);
-  if (GL(dl_phdr) == NULL)
 # endif
-    {
-      /* Starting from binutils-2.23, the linker will define the
-         magic symbol __ehdr_start to point to our own ELF header
-         if it is visible in a segment that also includes the phdrs.
-         So we can set up _dl_phdr and _dl_phnum even without any
-         information from auxv.  */
-
-      extern const ElfW(Ehdr) __ehdr_start
-# if BUILD_PIE_DEFAULT
-	__attribute__ ((visibility ("hidden")));
-# else
-	__attribute__ ((weak, visibility ("hidden")));
-      if (&__ehdr_start != NULL)
-# endif
-        {
-          assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
-          GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
-          GL(dl_phnum) = __ehdr_start.e_phnum;
-        }
-    }
 
   __tunables_init (__environ);
 
diff --git a/csu/libc-tls.c b/csu/libc-tls.c
index ca4def2613..51d3cf99bf 100644
--- a/csu/libc-tls.c
+++ b/csu/libc-tls.c
@@ -119,19 +119,18 @@ __libc_setup_tls (void)
   __tls_pre_init_tp ();
 
   /* Look through the TLS segment if there is any.  */
-  if (_dl_phdr != NULL)
-    for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
-      if (phdr->p_type == PT_TLS)
-	{
-	  /* Remember the values we need.  */
-	  memsz = phdr->p_memsz;
-	  filesz = phdr->p_filesz;
-	  initimage = (void *) phdr->p_vaddr + main_map->l_addr;
-	  align = phdr->p_align;
-	  if (phdr->p_align > max_align)
-	    max_align = phdr->p_align;
-	  break;
-	}
+  for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
+    if (phdr->p_type == PT_TLS)
+      {
+	/* Remember the values we need.  */
+	memsz = phdr->p_memsz;
+	filesz = phdr->p_filesz;
+	initimage = (void *) phdr->p_vaddr + main_map->l_addr;
+	align = phdr->p_align;
+	if (phdr->p_align > max_align)
+	  max_align = phdr->p_align;
+	break;
+      }
 
   /* Calculate the size of the static TLS surplus, with 0 auditors.  */
   _dl_tls_static_surplus_init (0);
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 614b5b3e0c..b5ec5bd6d1 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -250,12 +250,27 @@ _dl_aux_init (ElfW(auxv_t) *av)
 #endif
 
   _dl_auxv = av;
-  dl_parse_auxv_t auxv_values;
-  /* Use an explicit initialization loop here because memset may not
-     be available yet.  */
-  for (int i = 0; i < array_length (auxv_values); ++i)
-    auxv_values[i] = 0;
+  dl_parse_auxv_t auxv_values = { 0, };
   _dl_parse_auxv (av, auxv_values);
+
+  _dl_phdr = (void*) auxv_values[AT_PHDR];
+  _dl_phnum = auxv_values[AT_PHNUM];
+
+  if (_dl_phdr == NULL)
+    {
+      /* Starting from binutils-2.23, the linker will define the
+         magic symbol __ehdr_start to point to our own ELF header
+         if it is visible in a segment that also includes the phdrs.
+         So we can set up _dl_phdr and _dl_phnum even without any
+         information from auxv.  */
+
+      extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
+      assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
+      _dl_phdr = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
+      _dl_phnum = __ehdr_start.e_phnum;
+    }
+
+  assert (_dl_phdr != NULL);
 }
 #endif
 
@@ -324,20 +339,19 @@ _dl_non_dynamic_init (void)
   if (_dl_platform != NULL)
     _dl_platformlen = strlen (_dl_platform);
 
-  if (_dl_phdr != NULL)
-    for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
-      switch (ph->p_type)
-	{
-	/* Check if the stack is nonexecutable.  */
-	case PT_GNU_STACK:
-	  _dl_stack_flags = ph->p_flags;
-	  break;
-
-	case PT_GNU_RELRO:
-	  _dl_main_map.l_relro_addr = ph->p_vaddr;
-	  _dl_main_map.l_relro_size = ph->p_memsz;
-	  break;
-	}
+  for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
+    switch (ph->p_type)
+      {
+      /* Check if the stack is nonexecutable.  */
+      case PT_GNU_STACK:
+	_dl_stack_flags = ph->p_flags;
+	break;
+
+      case PT_GNU_RELRO:
+	_dl_main_map.l_relro_addr = ph->p_vaddr;
+	_dl_main_map.l_relro_size = ph->p_memsz;
+	break;
+      }
 
   call_function_static_weak (_dl_find_object_init);
 
diff --git a/sysdeps/unix/sysv/linux/dl-parse_auxv.h b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
index bf9374371e..2bf3a0ca6b 100644
--- a/sysdeps/unix/sysv/linux/dl-parse_auxv.h
+++ b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
@@ -21,6 +21,7 @@
 #include <fpu_control.h>
 #include <ldsodefs.h>
 #include <link.h>
+#include <dl-auxv.h>  /* For DL_PLATFORM_AUXV  */
 
 typedef ElfW(Addr) dl_parse_auxv_t[AT_MINSIGSTKSZ + 1];
 
-- 
2.34.1

--- End Message ---

--- End Message ---
--- Begin Message --- 
Source: glibc
Source-Version: 2.37-1
Done: Aurelien Jarno <aurel32@debian.org>

We believe that the bug you reported is fixed in the latest version of
glibc, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1028200@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Aurelien Jarno <aurel32@debian.org> (supplier of updated glibc package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Format: 1.8
Date: Tue, 16 May 2023 21:17:22 +0200
Source: glibc
Architecture: source
Version: 2.37-1
Distribution: experimental
Urgency: medium
Maintainer: GNU Libc Maintainers <debian-glibc@lists.debian.org>
Changed-By: Aurelien Jarno <aurel32@debian.org>
Closes: 806912 1028200
Changes:
 glibc (2.37-1) experimental; urgency=medium
 .
   [ Aurelien Jarno ]
   * New upstream release:
     - Fix GL(dl_phdr) and GL(dl_phnum) for static builds.  Closes: #1028200.
     - debian/symbols.wildcard: add 2.36 and GLIBC_ABI_DT_RELR.
     - debian/patches/localedata/locales-fr.diff: rebased.
     - debian/patches/alpha/local-string-functions.diff: rebased.
     - debian/patches/arm/git-atomic-compiler-builtins.diff: upstreamed.
     - debian/patches/hurd-i386/git-htl-pthread-self-early.diff: upstreamed.
     - debian/patches/hurd-i386/git-static-pie.diff: upstreamed.
     - debian/patches/hurd-i386/git-ipv6.diff: upstreamed.
     - debian/patches/hurd-i386/git-ip_mreqn.diff: upstreamed.
     - debian/patches/hurd-i386/git-bootstrap-enable_secure.diff: upstreamed.
     - debian/patches/hurd-i386/git-cond-destroy.diff: upstreamed.
     - debian/patches/hurd-i386/git-strerror_X.diff: upstreamed.
     - debian/patches/hurd-i386/git-xpg_strerror.diff: upstreamed.
     - debian/patches/hurd-i386/git-readlink-fifo.diff: upstreamed.
     - debian/patches/hurd-i386/git-net-route.h.diff: upstreamed.
     - debian/patches/hurd-i386/git-SOMAXCONN.diff: upstreamed.
     - debian/patches/hurd-i386/git-sigtimedwait.diff: upstreamed.
     - debian/patches/hurd-i386/git-getrandom-chroot.diff: upstreamed.
     - debian/patches/hurd-i386/git-mach-headers-freestanding.diff: upstreamed.
     - debian/patches/hurd-i386/git-sem_wait_race.diff: upstreamed.
     - debian/patches/hurd-i386/local-enable-ldconfig.diff: rebased.
     - debian/patches/any/local-ldso-disable-hwcap.diff: removed, obsolete.
     - debian/patches/any/local-ldconfig-multiarch.diff: rebased.
     - debian/patches/any/git-floatn-gcc-13-support.diff: upstreamed.
     - debian/patches/hurd-i386/submitted-net.diff: rebased.
     - debian/patches/hurd-i386/local-no-bootstrap-fs-access.diff: removed,
       obsolete.
   * Stop building libc6.1-alphaev67 package, as support for legacy hwcaps has
     been removed upstream:
     - debian/control.in/libc: add a conflicts against libc6.1-alphaev67 on
       alpha.
     - debian/control.in/opt: remove libc6.1-alphaev67 entry.
     - debian/patches/alpha/local-string-functions.diff: remove, obsolete.
     - debian/rules: drop DEBUG_libc6.1-alphaev67.
     - debian/script.in/nohwcap.sh: drop code to support libc6.1-alphaev67.
     debian/testsuite-xfail-debian.mk: simplify alpha condition.
   * Drop support for optimized packages from the packaging (Closes: #806912):
     - debian/control.in/opt: removed.
     - debian/rules.d/control.mk: drop support for including control.in/opt.
     - debian/script.in/nohwcap.sh: removed.
     - debian/rules.d/debhelper.mk: dropped code to include nohwcap.sh.
     - debian/debhelper.in/libc.postinst: removed call to nohwcap code.
     - debian/debhelper.in/libc.preinst: remove code creating
       /etc/ld.so.nohwcap.
     - debian/debhelper.in/glibc-source.lintian-overrides: removed otherbuild
       entries.
     - debian/debhelper.in/libc-otherbuild.*: removed.
   * debian/sysdeps/alpha.mk: temporarily build for EV56 until the baseline is
     raised at the GCC level.
 .
   [ Samuel Thibault ]
   * debian/patches/hurd-i386/git-tst-system.diff: Fix tst-system link.
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 91e3b13573d81b5736e9c09b5f8babbf5c8d4990 19503016 glibc_2.37.orig.tar.xz
 0212e35f39a12358209c2bb6e0fdb127749bb396 783592 glibc_2.37-1.debian.tar.xz
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Checksums-Sha256:
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Files:
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--- End Message ---
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