diff mbox series

[v9,1/3] elf: Add a test for PT_LOAD segments with mixed p_align [BZ #28676]

Message ID 20220121211205.268178-2-hjl.tools@gmail.com
State Committed
Headers show
Series Add p_align tests for PT_LOAD segments | expand

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Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

H.J. Lu Jan. 21, 2022, 9:12 p.m. UTC
Add tst-p_alignmod1-edit to edit the copy of tst-p_alignmod-base.so to
reduce p_align of the first PT_LOAD segment by half and verify that the
shared library is mapped with the maximum p_align of all PT_LOAD segments.
---
 elf/Makefile               |  17 +++++
 elf/tst-elf-edit.h         | 126 +++++++++++++++++++++++++++++++++++++
 elf/tst-p_align.h          |  20 ++++++
 elf/tst-p_align1.c         |  27 ++++++++
 elf/tst-p_alignmod-base.c  |  41 ++++++++++++
 elf/tst-p_alignmod1-edit.c |  27 ++++++++
 6 files changed, 258 insertions(+)
 create mode 100644 elf/tst-elf-edit.h
 create mode 100644 elf/tst-p_align.h
 create mode 100644 elf/tst-p_align1.c
 create mode 100644 elf/tst-p_alignmod-base.c
 create mode 100644 elf/tst-p_alignmod1-edit.c

Comments

Adhemerval Zanella Jan. 24, 2022, 2:16 p.m. UTC | #1
On 21/01/2022 18:12, H.J. Lu wrote:
> Add tst-p_alignmod1-edit to edit the copy of tst-p_alignmod-base.so to
> reduce p_align of the first PT_LOAD segment by half and verify that the
> shared library is mapped with the maximum p_align of all PT_LOAD segments.

LGTM, thanks.

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

> ---
>  elf/Makefile               |  17 +++++
>  elf/tst-elf-edit.h         | 126 +++++++++++++++++++++++++++++++++++++
>  elf/tst-p_align.h          |  20 ++++++
>  elf/tst-p_align1.c         |  27 ++++++++
>  elf/tst-p_alignmod-base.c  |  41 ++++++++++++
>  elf/tst-p_alignmod1-edit.c |  27 ++++++++
>  6 files changed, 258 insertions(+)
>  create mode 100644 elf/tst-elf-edit.h
>  create mode 100644 elf/tst-p_align.h
>  create mode 100644 elf/tst-p_align1.c
>  create mode 100644 elf/tst-p_alignmod-base.c
>  create mode 100644 elf/tst-p_alignmod1-edit.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 692a65b061..cdb41c686e 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -412,6 +412,8 @@ tests += \
>    tst-nodelete-opened \
>    tst-noload \
>    tst-null-argv \
> +  tst-p_alignmod1-edit \
> +  tst-p_align1 \
>    tst-relsort1 \
>    tst-ro-dynamic \
>    tst-rtld-run-static \
> @@ -728,6 +730,7 @@ modules-names = \
>    tst-nodelete-dlclose-plugin \
>    tst-nodelete-opened-lib \
>    tst-null-argv-lib \
> +  tst-p_alignmod-base \
>    tst-relsort1mod1 \
>    tst-relsort1mod2 \
>    tst-ro-dynamic-mod \
> @@ -2578,3 +2581,17 @@ CFLAGS-tst-dl_find_object-mod6.c += -funwind-tables
>  CFLAGS-tst-dl_find_object-mod7.c += -funwind-tables
>  CFLAGS-tst-dl_find_object-mod8.c += -funwind-tables
>  CFLAGS-tst-dl_find_object-mod9.c += -funwind-tables
> +
> +$(objpfx)tst-p_alignmod-base.so: $(libsupport)
> +LDFLAGS-tst-p_alignmod-base.so += -Wl,-z,max-page-size=0x200000
> +
> +$(objpfx)tst-p_align1: $(objpfx)tst-p_alignmod1.so
> +
> +# Make a copy of tst-p_alignmod-base.so and lower p_align of the first
> +# PT_LOAD segment.
> +$(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
> +			     $(objpfx)tst-p_alignmod-base.so
> +	rm -f $@
> +	cp $(objpfx)tst-p_alignmod-base.so $@
> +	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
> +	  $(objpfx)tst-p_alignmod1-edit $@
> diff --git a/elf/tst-elf-edit.h b/elf/tst-elf-edit.h
> new file mode 100644
> index 0000000000..b764e78933
> --- /dev/null
> +++ b/elf/tst-elf-edit.h
> @@ -0,0 +1,126 @@
> +/* Update p_align of the first PT_LOAD segment.
> +   Copyright (C) 2022 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 <stdio.h>
> +#include <stdbool.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <link.h>
> +#include <error.h>
> +#include <errno.h>
> +#include <sys/stat.h>
> +#include <sys/mman.h>
> +
> +const char *file_name;
> +
> +static size_t update_p_align (size_t);
> +
> +int
> +main (int argc, char ** argv)
> +{
> +  if (argc != 2)
> +    {
> +      printf ("Usage: %s: file\n", argv[0]);
> +      return 0;
> +    }
> +
> +  file_name = argv[1];
> +  struct stat statbuf;
> +  int errno_saved;
> +
> +  if (stat (file_name, &statbuf) < 0)
> +    error (1, errno, "%s: not exist", file_name);
> +
> +  ElfW(Ehdr) *ehdr;
> +
> +  if (statbuf.st_size < sizeof (*ehdr))
> +    error (1, 0, "%s: too small", file_name);
> +
> +  int fd = open (file_name, O_RDWR);
> +  if (fd < 0)
> +    error (1, errno, "%s: can't open", file_name);
> +
> +  /* Map in the whole file.  */
> +  void *base = mmap (NULL, statbuf.st_size, PROT_READ | PROT_WRITE,
> +		     MAP_SHARED, fd, 0);
> +  if (base == MAP_FAILED)
> +    {
> +      errno_saved = errno;
> +      close (fd);
> +      error (1, errno_saved, "%s: failed to map", file_name);
> +    }
> +
> +  ehdr = (ElfW(Ehdr) *) base;
> +  if (ehdr->e_ident[EI_MAG0] != ELFMAG0
> +      || ehdr->e_ident[EI_MAG1] != ELFMAG1
> +      || ehdr->e_ident[EI_MAG2] != ELFMAG2
> +      || ehdr->e_ident[EI_MAG3] != ELFMAG3)
> +    {
> +      close (fd);
> +      error (1, 0, "%s: bad ELF header", file_name);
> +    }
> +
> +  if (ehdr->e_type != ET_DYN)
> +    {
> +      close (fd);
> +      error (1, 0, "%s: not shared library", file_name);
> +    }
> +
> +  bool unsupported_class = true;
> +  switch (ehdr->e_ident[EI_CLASS])
> +    {
> +    default:
> +      break;
> +
> +    case ELFCLASS32:
> +      unsupported_class = __ELF_NATIVE_CLASS != 32;
> +      break;
> +
> +    case ELFCLASS64:
> +      unsupported_class = __ELF_NATIVE_CLASS != 64;
> +      break;
> +    }
> +
> +  if (unsupported_class)
> +    {
> +      close (fd);
> +      error (1, 0, "%s: unsupported ELF class: %d",
> +	     file_name, ehdr->e_ident[EI_CLASS]);
> +    }
> +
> +  size_t phdr_size = sizeof (ElfW(Phdr)) * ehdr->e_phentsize;
> +  if (statbuf.st_size < (ehdr->e_phoff + phdr_size))
> +    {
> +      close (fd);
> +      error (1, 0, "%s: too small", file_name);
> +    }
> +
> +  ElfW(Phdr) *phdr = (ElfW(Phdr) *) (base + ehdr->e_phoff);
> +  for (int i = 0; i < ehdr->e_phnum; i++, phdr++)
> +    if (phdr->p_type == PT_LOAD)
> +      {
> +	/* Update p_align of the first PT_LOAD segment.  */
> +	phdr->p_align = update_p_align (phdr->p_align);
> +	break;
> +      }
> +
> +  munmap (base, statbuf.st_size);
> +  close (fd);
> +
> +  return 0;
> +}
> diff --git a/elf/tst-p_align.h b/elf/tst-p_align.h
> new file mode 100644
> index 0000000000..cef92330fb
> --- /dev/null
> +++ b/elf/tst-p_align.h
> @@ -0,0 +1,20 @@
> +/* Prototypes to check different alignments of PT_LOAD segments in
> +   a shared library.
> +   Copyright (C) 2022 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/>.  */
> +
> +extern int do_load_test (void);
> diff --git a/elf/tst-p_align1.c b/elf/tst-p_align1.c
> new file mode 100644
> index 0000000000..961c7fbbf1
> --- /dev/null
> +++ b/elf/tst-p_align1.c
> @@ -0,0 +1,27 @@
> +/* Check different alignments of PT_LOAD segments in a shared library.
> +   Copyright (C) 2022 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 "tst-p_align.h"
> +
> +static int
> +do_test (void)
> +{
> +  return do_load_test ();
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/elf/tst-p_alignmod-base.c b/elf/tst-p_alignmod-base.c
> new file mode 100644
> index 0000000000..0fc1b75523
> --- /dev/null
> +++ b/elf/tst-p_alignmod-base.c
> @@ -0,0 +1,41 @@
> +/* Check alignment of PT_LOAD segment in a shared library.
> +   Copyright (C) 2022 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 <stdio.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <support/check.h>
> +#include <tst-file-align.h>
> +#include "tst-p_align.h"
> +
> +int foo __attribute__ ((aligned (ALIGN))) = 1;
> +
> +bool
> +__attribute__ ((weak, noclone, noinline))
> +is_aligned_p (void *p, int align)
> +{
> +  return (((uintptr_t) p) & (align - 1)) == 0;
> +}
> +
> +int
> +do_load_test (void)
> +{
> +  printf ("foo: %p\n", &foo);
> +  TEST_VERIFY (is_aligned_p (&foo, ALIGN));
> +  return 0;
> +}
> diff --git a/elf/tst-p_alignmod1-edit.c b/elf/tst-p_alignmod1-edit.c
> new file mode 100644
> index 0000000000..06d9c636fd
> --- /dev/null
> +++ b/elf/tst-p_alignmod1-edit.c
> @@ -0,0 +1,27 @@
> +/* Reduce p_align of the first PT_LOAD segment by half.
> +   Copyright (C) 2022 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 "tst-elf-edit.h"
> +
> +/* Reduce p_align by half.  */
> +
> +static size_t
> +update_p_align (size_t p_align)
> +{
> +  return p_align >> 1;
> +}
Joseph Myers Jan. 24, 2022, 9:21 p.m. UTC | #2
On Mon, 24 Jan 2022, Adhemerval Zanella via Libc-alpha wrote:

> > +# Make a copy of tst-p_alignmod-base.so and lower p_align of the first
> > +# PT_LOAD segment.
> > +$(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
> > +			     $(objpfx)tst-p_alignmod-base.so
> > +	rm -f $@
> > +	cp $(objpfx)tst-p_alignmod-base.so $@
> > +	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
> > +	  $(objpfx)tst-p_alignmod1-edit $@

This has broken the testsuite build for all cross-compilation situations 
not running the newly built tests.  You can't run a program built with the 
new glibc unless $(run-built-tests) is yes.  Either disable everything 
depending on running these programs unless $(run-built-tests) is yes or 
revert the commits adding them (reimplementing the editing in Python using 
only the standard library might be a possibility for the future; building 
the C program for $build wouldn't be a good idea and we'd like to phase 
out the remaining two tests that do use C programs for $build by subsuming 
them in conformtest).
Adhemerval Zanella Jan. 25, 2022, 11:33 a.m. UTC | #3
On 24/01/2022 18:21, Joseph Myers wrote:
> On Mon, 24 Jan 2022, Adhemerval Zanella via Libc-alpha wrote:
> 
>>> +# Make a copy of tst-p_alignmod-base.so and lower p_align of the first
>>> +# PT_LOAD segment.
>>> +$(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
>>> +			     $(objpfx)tst-p_alignmod-base.so
>>> +	rm -f $@
>>> +	cp $(objpfx)tst-p_alignmod-base.so $@
>>> +	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
>>> +	  $(objpfx)tst-p_alignmod1-edit $@
> 
> This has broken the testsuite build for all cross-compilation situations 
> not running the newly built tests.  You can't run a program built with the 
> new glibc unless $(run-built-tests) is yes.  Either disable everything 
> depending on running these programs unless $(run-built-tests) is yes or 
> revert the commits adding them (reimplementing the editing in Python using 
> only the standard library might be a possibility for the future; building 
> the C program for $build wouldn't be a good idea and we'd like to phase 
> out the remaining two tests that do use C programs for $build by subsuming 
> them in conformtest).
> 

I forgot about this issue and reimplementing using pythong seems a better
approach. I will work on this.
Florian Weimer Jan. 26, 2022, 10:02 a.m. UTC | #4
* Adhemerval Zanella:

> On 24/01/2022 18:21, Joseph Myers wrote:
>> On Mon, 24 Jan 2022, Adhemerval Zanella via Libc-alpha wrote:
>> 
>>>> +# Make a copy of tst-p_alignmod-base.so and lower p_align of the first
>>>> +# PT_LOAD segment.
>>>> +$(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
>>>> +			     $(objpfx)tst-p_alignmod-base.so
>>>> +	rm -f $@
>>>> +	cp $(objpfx)tst-p_alignmod-base.so $@
>>>> +	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
>>>> +	  $(objpfx)tst-p_alignmod1-edit $@
>> 
>> This has broken the testsuite build for all cross-compilation situations 
>> not running the newly built tests.  You can't run a program built with the 
>> new glibc unless $(run-built-tests) is yes.  Either disable everything 
>> depending on running these programs unless $(run-built-tests) is yes or 
>> revert the commits adding them (reimplementing the editing in Python using 
>> only the standard library might be a possibility for the future; building 
>> the C program for $build wouldn't be a good idea and we'd like to phase 
>> out the remaining two tests that do use C programs for $build by subsuming 
>> them in conformtest).
>> 
>
> I forgot about this issue and reimplementing using pythong seems a better
> approach. I will work on this.

Can we revert the test addition in the meantime?  It's making validation
of other changes complicated.

Thanks,
Florian
diff mbox series

Patch

diff --git a/elf/Makefile b/elf/Makefile
index 692a65b061..cdb41c686e 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -412,6 +412,8 @@  tests += \
   tst-nodelete-opened \
   tst-noload \
   tst-null-argv \
+  tst-p_alignmod1-edit \
+  tst-p_align1 \
   tst-relsort1 \
   tst-ro-dynamic \
   tst-rtld-run-static \
@@ -728,6 +730,7 @@  modules-names = \
   tst-nodelete-dlclose-plugin \
   tst-nodelete-opened-lib \
   tst-null-argv-lib \
+  tst-p_alignmod-base \
   tst-relsort1mod1 \
   tst-relsort1mod2 \
   tst-ro-dynamic-mod \
@@ -2578,3 +2581,17 @@  CFLAGS-tst-dl_find_object-mod6.c += -funwind-tables
 CFLAGS-tst-dl_find_object-mod7.c += -funwind-tables
 CFLAGS-tst-dl_find_object-mod8.c += -funwind-tables
 CFLAGS-tst-dl_find_object-mod9.c += -funwind-tables
+
+$(objpfx)tst-p_alignmod-base.so: $(libsupport)
+LDFLAGS-tst-p_alignmod-base.so += -Wl,-z,max-page-size=0x200000
+
+$(objpfx)tst-p_align1: $(objpfx)tst-p_alignmod1.so
+
+# Make a copy of tst-p_alignmod-base.so and lower p_align of the first
+# PT_LOAD segment.
+$(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
+			     $(objpfx)tst-p_alignmod-base.so
+	rm -f $@
+	cp $(objpfx)tst-p_alignmod-base.so $@
+	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
+	  $(objpfx)tst-p_alignmod1-edit $@
diff --git a/elf/tst-elf-edit.h b/elf/tst-elf-edit.h
new file mode 100644
index 0000000000..b764e78933
--- /dev/null
+++ b/elf/tst-elf-edit.h
@@ -0,0 +1,126 @@ 
+/* Update p_align of the first PT_LOAD segment.
+   Copyright (C) 2022 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 <stdio.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <link.h>
+#include <error.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+const char *file_name;
+
+static size_t update_p_align (size_t);
+
+int
+main (int argc, char ** argv)
+{
+  if (argc != 2)
+    {
+      printf ("Usage: %s: file\n", argv[0]);
+      return 0;
+    }
+
+  file_name = argv[1];
+  struct stat statbuf;
+  int errno_saved;
+
+  if (stat (file_name, &statbuf) < 0)
+    error (1, errno, "%s: not exist", file_name);
+
+  ElfW(Ehdr) *ehdr;
+
+  if (statbuf.st_size < sizeof (*ehdr))
+    error (1, 0, "%s: too small", file_name);
+
+  int fd = open (file_name, O_RDWR);
+  if (fd < 0)
+    error (1, errno, "%s: can't open", file_name);
+
+  /* Map in the whole file.  */
+  void *base = mmap (NULL, statbuf.st_size, PROT_READ | PROT_WRITE,
+		     MAP_SHARED, fd, 0);
+  if (base == MAP_FAILED)
+    {
+      errno_saved = errno;
+      close (fd);
+      error (1, errno_saved, "%s: failed to map", file_name);
+    }
+
+  ehdr = (ElfW(Ehdr) *) base;
+  if (ehdr->e_ident[EI_MAG0] != ELFMAG0
+      || ehdr->e_ident[EI_MAG1] != ELFMAG1
+      || ehdr->e_ident[EI_MAG2] != ELFMAG2
+      || ehdr->e_ident[EI_MAG3] != ELFMAG3)
+    {
+      close (fd);
+      error (1, 0, "%s: bad ELF header", file_name);
+    }
+
+  if (ehdr->e_type != ET_DYN)
+    {
+      close (fd);
+      error (1, 0, "%s: not shared library", file_name);
+    }
+
+  bool unsupported_class = true;
+  switch (ehdr->e_ident[EI_CLASS])
+    {
+    default:
+      break;
+
+    case ELFCLASS32:
+      unsupported_class = __ELF_NATIVE_CLASS != 32;
+      break;
+
+    case ELFCLASS64:
+      unsupported_class = __ELF_NATIVE_CLASS != 64;
+      break;
+    }
+
+  if (unsupported_class)
+    {
+      close (fd);
+      error (1, 0, "%s: unsupported ELF class: %d",
+	     file_name, ehdr->e_ident[EI_CLASS]);
+    }
+
+  size_t phdr_size = sizeof (ElfW(Phdr)) * ehdr->e_phentsize;
+  if (statbuf.st_size < (ehdr->e_phoff + phdr_size))
+    {
+      close (fd);
+      error (1, 0, "%s: too small", file_name);
+    }
+
+  ElfW(Phdr) *phdr = (ElfW(Phdr) *) (base + ehdr->e_phoff);
+  for (int i = 0; i < ehdr->e_phnum; i++, phdr++)
+    if (phdr->p_type == PT_LOAD)
+      {
+	/* Update p_align of the first PT_LOAD segment.  */
+	phdr->p_align = update_p_align (phdr->p_align);
+	break;
+      }
+
+  munmap (base, statbuf.st_size);
+  close (fd);
+
+  return 0;
+}
diff --git a/elf/tst-p_align.h b/elf/tst-p_align.h
new file mode 100644
index 0000000000..cef92330fb
--- /dev/null
+++ b/elf/tst-p_align.h
@@ -0,0 +1,20 @@ 
+/* Prototypes to check different alignments of PT_LOAD segments in
+   a shared library.
+   Copyright (C) 2022 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/>.  */
+
+extern int do_load_test (void);
diff --git a/elf/tst-p_align1.c b/elf/tst-p_align1.c
new file mode 100644
index 0000000000..961c7fbbf1
--- /dev/null
+++ b/elf/tst-p_align1.c
@@ -0,0 +1,27 @@ 
+/* Check different alignments of PT_LOAD segments in a shared library.
+   Copyright (C) 2022 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 "tst-p_align.h"
+
+static int
+do_test (void)
+{
+  return do_load_test ();
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-p_alignmod-base.c b/elf/tst-p_alignmod-base.c
new file mode 100644
index 0000000000..0fc1b75523
--- /dev/null
+++ b/elf/tst-p_alignmod-base.c
@@ -0,0 +1,41 @@ 
+/* Check alignment of PT_LOAD segment in a shared library.
+   Copyright (C) 2022 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 <stdio.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <support/check.h>
+#include <tst-file-align.h>
+#include "tst-p_align.h"
+
+int foo __attribute__ ((aligned (ALIGN))) = 1;
+
+bool
+__attribute__ ((weak, noclone, noinline))
+is_aligned_p (void *p, int align)
+{
+  return (((uintptr_t) p) & (align - 1)) == 0;
+}
+
+int
+do_load_test (void)
+{
+  printf ("foo: %p\n", &foo);
+  TEST_VERIFY (is_aligned_p (&foo, ALIGN));
+  return 0;
+}
diff --git a/elf/tst-p_alignmod1-edit.c b/elf/tst-p_alignmod1-edit.c
new file mode 100644
index 0000000000..06d9c636fd
--- /dev/null
+++ b/elf/tst-p_alignmod1-edit.c
@@ -0,0 +1,27 @@ 
+/* Reduce p_align of the first PT_LOAD segment by half.
+   Copyright (C) 2022 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 "tst-elf-edit.h"
+
+/* Reduce p_align by half.  */
+
+static size_t
+update_p_align (size_t p_align)
+{
+  return p_align >> 1;
+}