[PATCH v8 0/4] Properly align all PT_LOAD segments with tests

[PATCH v8 0/4] Properly align all PT_LOAD segments with tests

[H.J. Lu]

Changes from v7:

1. Skip non-power of two alignment when considering the maximum p_align.
2. Add tst-p_alignmod-base.c to build tst-p_alignmod-base.so with

bool
__attribute__ ((weak, noclone, noinline))
is_aligned_p (void *p, int align)
{
  return (((uintptr_t) p) & (align - 1)) == 0;
}

3. Update the Copyright year.

Changes from v6:

1. Rebase.
2. Add tests for other p_align cases.

Linker may set p_align of a PT_LOAD segment larger than p_align of the
first PT_LOAD segment to satisfy a section alignment.  We should align
the first PT_LOAD segment to the maximum p_align of all PT_LOAD segments.


H.J. Lu (4):
  elf: Properly align all PT_LOAD segments [BZ #28676]
  elf: Add a test for PT_LOAD segments with mixed p_align [BZ #28676]
  elf: Add a test for PT_LOAD segments with p_align == 1 [BZ #28688]
  elf: Add a test for PT_LOAD segments with invalid p_align [BZ #28688]

 elf/Makefile               |  38 +++++++++++
 elf/dl-load.c              |   9 ++-
 elf/tst-elf-edit.h         | 126 +++++++++++++++++++++++++++++++++++++
 elf/tst-p_align.h          |  20 ++++++
 elf/tst-p_align1.c         |  27 ++++++++
 elf/tst-p_align2.c         |  27 ++++++++
 elf/tst-p_align3.c         |  27 ++++++++
 elf/tst-p_align3.sh        |  27 ++++++++
 elf/tst-p_alignmod-base.c  |  41 ++++++++++++
 elf/tst-p_alignmod1-edit.c |  34 ++++++++++
 elf/tst-p_alignmod2-edit.c |  27 ++++++++
 elf/tst-p_alignmod3.c      |  25 ++++++++
 12 files changed, 427 insertions(+), 1 deletion(-)
 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_align2.c
 create mode 100644 elf/tst-p_align3.c
 create mode 100755 elf/tst-p_align3.sh
 create mode 100644 elf/tst-p_alignmod-base.c
 create mode 100644 elf/tst-p_alignmod1-edit.c
 create mode 100644 elf/tst-p_alignmod2-edit.c
 create mode 100644 elf/tst-p_alignmod3.c

-- 
2.34.1

[PATCH v8 1/4] elf: Properly align all PT_LOAD segments [BZ #28676]

[H.J. Lu]

Linker may set p_align of a PT_LOAD segment larger than p_align of the
first PT_LOAD segment to satisfy a section alignment:

Elf file type is DYN (Shared object file)
Entry point 0x0
There are 10 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000834 0x0000000000000834  R E    0x1000
  LOAD           0x0000000000000e00 0x0000000000001e00 0x0000000000001e00
                 0x0000000000000230 0x0000000000000230  RW     0x1000
  LOAD           0x0000000000400000 0x0000000000400000 0x0000000000400000
                 0x0000000000000004 0x0000000000000008  RW     0x400000
...

 Section to Segment mapping:
  Segment Sections...
   00     .note.gnu.property .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame
   01     .init_array .fini_array .data.rel.ro .dynamic .got .got.plt
   02     .data .bss

We should align the first PT_LOAD segment to the maximum p_align of all
PT_LOAD segments, similar to the kernel commit:

commit ce81bb256a224259ab686742a6284930cbe4f1fa
Author: Chris Kennelly <ckennelly@google.com>
Date:   Thu Oct 15 20:12:32 2020 -0700

    fs/binfmt_elf: use PT_LOAD p_align values for suitable start address
---
 elf/dl-load.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 12744caf91..5b0ff41ee1 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1101,6 +1101,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
     size_t nloadcmds = 0;
     bool has_holes = false;
     bool empty_dynamic = false;
+    ElfW(Addr) p_align_max = 0;
 
     /* The struct is initialized to zero so this is not necessary:
     l->l_ld = 0;
@@ -1146,7 +1147,9 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	  c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
 	  c->dataend = ph->p_vaddr + ph->p_filesz;
 	  c->allocend = ph->p_vaddr + ph->p_memsz;
-	  c->mapalign = ph->p_align;
+	  /* Remember the maximum p_align.  */
+	  if (powerof2 (ph->p_align) && ph->p_align > p_align_max)
+	    p_align_max = ph->p_align;
 	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
 
 	  /* Determine whether there is a gap between the last segment
@@ -1221,6 +1224,10 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	goto lose;
       }
 
+    /* Align all PT_LOAD segments to the maximum p_align.  */
+    for (size_t i = 0; i < nloadcmds; i++)
+      loadcmds[i].mapalign = p_align_max;
+
     /* dlopen of an executable is not valid because it is not possible
        to perform proper relocations, handle static TLS, or run the
        ELF constructors.  For PIE, the check needs the dynamic
-- 
2.34.1

[PATCH v8 2/4] elf: Add a test for PT_LOAD segments with mixed p_align [BZ #28676]

[H.J. Lu]

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               |  16 +++++
 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 |  34 ++++++++++
 6 files changed, 264 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..94ebcab1fa 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 +2581,16 @@ 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: $(libsupport)
+
+$(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..cdb453e696
--- /dev/null
+++ b/elf/tst-p_alignmod1-edit.c
@@ -0,0 +1,34 @@
+/* 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)
+{
+  size_t pagesize = sysconf (_SC_PAGESIZE);
+  size_t new_p_align = p_align >> 1;
+
+  if (new_p_align >= pagesize)
+    error (1, 0, "%s: new p_align (0x%zx) >= page size (0x%zx)",
+	   file_name, new_p_align, pagesize);
+
+  return new_p_align;
+}
-- 
2.34.1

[PATCH v8 3/4] elf: Add a test for PT_LOAD segments with p_align == 1 [BZ #28688]

[H.J. Lu]

Add tst-p_alignmod2-edit to edit the copy of tst-p_alignmod-base.so to
set p_align of the first PT_LOAD segment to 1 and verify that the shared
library can be loaded normally.
---
 elf/Makefile               | 13 +++++++++++++
 elf/tst-p_align2.c         | 27 +++++++++++++++++++++++++++
 elf/tst-p_alignmod2-edit.c | 27 +++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)
 create mode 100644 elf/tst-p_align2.c
 create mode 100644 elf/tst-p_alignmod2-edit.c

diff --git a/elf/Makefile b/elf/Makefile
index 94ebcab1fa..92a6a3baf1 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -413,7 +413,9 @@ tests += \
   tst-noload \
   tst-null-argv \
   tst-p_alignmod1-edit \
+  tst-p_alignmod2-edit \
   tst-p_align1 \
+  tst-p_align2 \
   tst-relsort1 \
   tst-ro-dynamic \
   tst-rtld-run-static \
@@ -2594,3 +2596,14 @@ $(objpfx)tst-p_alignmod1.so: $(objpfx)tst-p_alignmod1-edit \
 	cp $(objpfx)tst-p_alignmod-base.so $@
 	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
 	  $(objpfx)tst-p_alignmod1-edit $@
+
+$(objpfx)tst-p_align2: $(objpfx)tst-p_alignmod2.so
+
+# Make a copy of tst-p_alignmod-base.so and update p_align of the first
+# PT_LOAD segment.
+$(objpfx)tst-p_alignmod2.so: $(objpfx)tst-p_alignmod2-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_alignmod2-edit $@
diff --git a/elf/tst-p_align2.c b/elf/tst-p_align2.c
new file mode 100644
index 0000000000..961c7fbbf1
--- /dev/null
+++ b/elf/tst-p_align2.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_alignmod2-edit.c b/elf/tst-p_alignmod2-edit.c
new file mode 100644
index 0000000000..4c2ae65b4e
--- /dev/null
+++ b/elf/tst-p_alignmod2-edit.c
@@ -0,0 +1,27 @@
+/* Set p_align of the first PT_LOAD segment to 1.
+   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"
+
+/* Set p_align to 1.  */
+
+static size_t
+update_p_align (size_t p_align __attribute__ ((unused)))
+{
+  return 1;
+}
-- 
2.34.1

[PATCH v8 4/4] elf: Add a test for PT_LOAD segments with invalid p_align [BZ #28688]

[H.J. Lu]

Build tst-p_alignmod3.so with 256 byte page size and verify that it is
rejected with a proper error message.
---
 elf/Makefile          |  9 +++++++++
 elf/tst-p_align3.c    | 27 +++++++++++++++++++++++++++
 elf/tst-p_align3.sh   | 27 +++++++++++++++++++++++++++
 elf/tst-p_alignmod3.c | 25 +++++++++++++++++++++++++
 4 files changed, 88 insertions(+)
 create mode 100644 elf/tst-p_align3.c
 create mode 100755 elf/tst-p_align3.sh
 create mode 100644 elf/tst-p_alignmod3.c

diff --git a/elf/Makefile b/elf/Makefile
index 92a6a3baf1..d3232ce5ff 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -416,6 +416,7 @@ tests += \
   tst-p_alignmod2-edit \
   tst-p_align1 \
   tst-p_align2 \
+  tst-p_align3 \
   tst-relsort1 \
   tst-ro-dynamic \
   tst-rtld-run-static \
@@ -733,6 +734,7 @@ modules-names = \
   tst-nodelete-opened-lib \
   tst-null-argv-lib \
   tst-p_alignmod-base \
+  tst-p_alignmod3 \
   tst-relsort1mod1 \
   tst-relsort1mod2 \
   tst-ro-dynamic-mod \
@@ -2607,3 +2609,10 @@ $(objpfx)tst-p_alignmod2.so: $(objpfx)tst-p_alignmod2-edit \
 	cp $(objpfx)tst-p_alignmod-base.so $@
 	$(test-wrapper-env) $(run-program-env) $(rtld-prefix) \
 	  $(objpfx)tst-p_alignmod2-edit $@
+
+LDFLAGS-tst-p_alignmod3.so += -Wl,-z,max-page-size=0x100,-z,common-page-size=0x100
+
+$(objpfx)tst-p_align3: $(objpfx)tst-p_alignmod3.so
+$(objpfx)tst-p_align3.out: tst-p_align3.sh $(objpfx)tst-p_align3
+	$(SHELL) $< $(common-objpfx) '$(test-program-prefix)'; \
+	$(evaluate-test)
diff --git a/elf/tst-p_align3.c b/elf/tst-p_align3.c
new file mode 100644
index 0000000000..8be9f311bd
--- /dev/null
+++ b/elf/tst-p_align3.c
@@ -0,0 +1,27 @@
+/* Check invalid p_align 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_align3.sh b/elf/tst-p_align3.sh
new file mode 100755
index 0000000000..688c4b34cc
--- /dev/null
+++ b/elf/tst-p_align3.sh
@@ -0,0 +1,27 @@
+#!/bin/sh
+# Check invalid p_align 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/>.
+
+common_objpfx=$1; shift
+test_program_prefix=$1; shift
+
+${test_program_prefix} \
+  ${common_objpfx}elf/tst-p_align3 \
+    2> ${common_objpfx}elf/tst-p_align3.out
+test $? -ne 127 && exit 1
+grep "ELF load command address/offset not page-aligned" ${common_objpfx}elf/tst-p_align3.out
diff --git a/elf/tst-p_alignmod3.c b/elf/tst-p_alignmod3.c
new file mode 100644
index 0000000000..c15de3d6f2
--- /dev/null
+++ b/elf/tst-p_alignmod3.c
@@ -0,0 +1,25 @@
+/* Check invalid p_align 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 "tst-p_align.h"
+
+int
+do_load_test (void)
+{
+  return 0;
+}
-- 
2.34.1

Re: [PATCH v8 1/4] elf: Properly align all PT_LOAD segments [BZ #28676]

[Adhemerval Zanella]

On 18/01/2022 18:57, H.J. Lu wrote:
> Linker may set p_align of a PT_LOAD segment larger than p_align of the
> first PT_LOAD segment to satisfy a section alignment:
> 
> Elf file type is DYN (Shared object file)
> Entry point 0x0
> There are 10 program headers, starting at offset 64
> 
> Program Headers:
>   Type           Offset             VirtAddr           PhysAddr
>                  FileSiz            MemSiz              Flags  Align
>   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
>                  0x0000000000000834 0x0000000000000834  R E    0x1000
>   LOAD           0x0000000000000e00 0x0000000000001e00 0x0000000000001e00
>                  0x0000000000000230 0x0000000000000230  RW     0x1000
>   LOAD           0x0000000000400000 0x0000000000400000 0x0000000000400000
>                  0x0000000000000004 0x0000000000000008  RW     0x400000
> ...
> 
>  Section to Segment mapping:
>   Segment Sections...
>    00     .note.gnu.property .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame
>    01     .init_array .fini_array .data.rel.ro .dynamic .got .got.plt
>    02     .data .bss
> 
> We should align the first PT_LOAD segment to the maximum p_align of all
> PT_LOAD segments, similar to the kernel commit:
> 
> commit ce81bb256a224259ab686742a6284930cbe4f1fa
> Author: Chris Kennelly <ckennelly@google.com>
> Date:   Thu Oct 15 20:12:32 2020 -0700
> 
>     fs/binfmt_elf: use PT_LOAD p_align values for suitable start address

LGTM, thanks.

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

> ---
>  elf/dl-load.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index 12744caf91..5b0ff41ee1 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1101,6 +1101,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>      size_t nloadcmds = 0;
>      bool has_holes = false;
>      bool empty_dynamic = false;
> +    ElfW(Addr) p_align_max = 0;
>  
>      /* The struct is initialized to zero so this is not necessary:
>      l->l_ld = 0;
> @@ -1146,7 +1147,9 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>  	  c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
>  	  c->dataend = ph->p_vaddr + ph->p_filesz;
>  	  c->allocend = ph->p_vaddr + ph->p_memsz;
> -	  c->mapalign = ph->p_align;
> +	  /* Remember the maximum p_align.  */
> +	  if (powerof2 (ph->p_align) && ph->p_align > p_align_max)
> +	    p_align_max = ph->p_align;
>  	  c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
>  
>  	  /* Determine whether there is a gap between the last segment
> @@ -1221,6 +1224,10 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>  	goto lose;
>        }
>  
> +    /* Align all PT_LOAD segments to the maximum p_align.  */
> +    for (size_t i = 0; i < nloadcmds; i++)
> +      loadcmds[i].mapalign = p_align_max;
> +
>      /* dlopen of an executable is not valid because it is not possible
>         to perform proper relocations, handle static TLS, or run the
>         ELF constructors.  For PIE, the check needs the dynamic

Re: [PATCH v8 2/4] elf: Add a test for PT_LOAD segments with mixed p_align [BZ #28676]

[Adhemerval Zanella]

On 18/01/2022 18:57, 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.
> ---
>  elf/Makefile               |  16 +++++
>  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 |  34 ++++++++++
>  6 files changed, 264 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..94ebcab1fa 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 +2581,16 @@ 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: $(libsupport)
> +
> +$(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>

I am seeing a failure with GNU ld (GNU Binutils) 2.37.20220112:

$ make test t=elf/tst-p_align1
[...]
FAIL: elf/tst-p_align1
original exit status 1
foo: 0x7fdddbecb000
error: tst-p_alignmod-base.c:39: not true: is_aligned_p (&foo, ALIGN)
error: 1 test failures

Without -Wl,-z,max-page-size=0x200000 the tst-p_alignmod-base.so is still
0x1000:

$ readelf -l elf/tst-p_alignmod-base.so 
[...]
Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000998 0x0000000000000998  R      0x1000
  LOAD           0x0000000000001000 0x0000000000001000 0x0000000000001000
                 0x0000000000000589 0x0000000000000589  R E    0x1000
  LOAD           0x0000000000002000 0x0000000000002000 0x0000000000002000
                 0x00000000000003f8 0x00000000000003f8  R      0x1000
  LOAD           0x0000000000002df0 0x0000000000003df0 0x0000000000003df0
                 0x0000000000000288 0x0000000000000288  RW     0x1000
  LOAD           0x0000000000200000 0x0000000000200000 0x0000000000200000
                 0x0000000000200004 0x0000000000200018  RW     0x1000
[...]

I think you will need to use the same strategy from tst-align3 to force the
maximum alignment:

diff --git a/elf/Makefile b/elf/Makefile
index 94ebcab1fa..cdb41c686e 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -2583,6 +2583,7 @@ 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
 
diff --git a/elf/tst-p_alignmod1-edit.c b/elf/tst-p_alignmod1-edit.c
index cdb453e696..06d9c636fd 100644
--- a/elf/tst-p_alignmod1-edit.c
+++ b/elf/tst-p_alignmod1-edit.c
@@ -23,12 +23,5 @@
 static size_t
 update_p_align (size_t p_align)
 {
-  size_t pagesize = sysconf (_SC_PAGESIZE);
-  size_t new_p_align = p_align >> 1;
-
-  if (new_p_align >= pagesize)
-    error (1, 0, "%s: new p_align (0x%zx) >= page size (0x%zx)",
-          file_name, new_p_align, pagesize);
-
-  return new_p_align;
+  return p_align >> 1;
 }

The rest looks ok.

> 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..cdb453e696
> --- /dev/null
> +++ b/elf/tst-p_alignmod1-edit.c
> @@ -0,0 +1,34 @@
> +/* 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)
> +{
> +  size_t pagesize = sysconf (_SC_PAGESIZE);
> +  size_t new_p_align = p_align >> 1;
> +
> +  if (new_p_align >= pagesize)
> +    error (1, 0, "%s: new p_align (0x%zx) >= page size (0x%zx)",
> +	   file_name, new_p_align, pagesize);
> +
> +  return new_p_align;
> +}

Re: [PATCH v8 2/4] elf: Add a test for PT_LOAD segments with mixed p_align [BZ #28676]

[H.J. Lu]

On Fri, Jan 21, 2022 at 12:00 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> On 18/01/2022 18:57, 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.
> > ---
> >  elf/Makefile               |  16 +++++
> >  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 |  34 ++++++++++
> >  6 files changed, 264 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..94ebcab1fa 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 +2581,16 @@ 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: $(libsupport)
> > +
> > +$(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>
>
> I am seeing a failure with GNU ld (GNU Binutils) 2.37.20220112:
>
> $ make test t=elf/tst-p_align1
> [...]
> FAIL: elf/tst-p_align1
> original exit status 1
> foo: 0x7fdddbecb000
> error: tst-p_alignmod-base.c:39: not true: is_aligned_p (&foo, ALIGN)
> error: 1 test failures
>
> Without -Wl,-z,max-page-size=0x200000 the tst-p_alignmod-base.so is still
> 0x1000:
>
> $ readelf -l elf/tst-p_alignmod-base.so
> [...]
> Program Headers:
>   Type           Offset             VirtAddr           PhysAddr
>                  FileSiz            MemSiz              Flags  Align
>   LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
>                  0x0000000000000998 0x0000000000000998  R      0x1000
>   LOAD           0x0000000000001000 0x0000000000001000 0x0000000000001000
>                  0x0000000000000589 0x0000000000000589  R E    0x1000
>   LOAD           0x0000000000002000 0x0000000000002000 0x0000000000002000
>                  0x00000000000003f8 0x00000000000003f8  R      0x1000
>   LOAD           0x0000000000002df0 0x0000000000003df0 0x0000000000003df0
>                  0x0000000000000288 0x0000000000000288  RW     0x1000
>   LOAD           0x0000000000200000 0x0000000000200000 0x0000000000200000
>                  0x0000000000200004 0x0000000000200018  RW     0x1000
> [...]
>
> I think you will need to use the same strategy from tst-align3 to force the
> maximum alignment:
>
> diff --git a/elf/Makefile b/elf/Makefile
> index 94ebcab1fa..cdb41c686e 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -2583,6 +2583,7 @@ 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

Fixed.

>  $(objpfx)tst-p_align1: $(objpfx)tst-p_alignmod1.so
>
> diff --git a/elf/tst-p_alignmod1-edit.c b/elf/tst-p_alignmod1-edit.c
> index cdb453e696..06d9c636fd 100644
> --- a/elf/tst-p_alignmod1-edit.c
> +++ b/elf/tst-p_alignmod1-edit.c
> @@ -23,12 +23,5 @@
>  static size_t
>  update_p_align (size_t p_align)
>  {
> -  size_t pagesize = sysconf (_SC_PAGESIZE);
> -  size_t new_p_align = p_align >> 1;
> -
> -  if (new_p_align >= pagesize)
> -    error (1, 0, "%s: new p_align (0x%zx) >= page size (0x%zx)",
> -          file_name, new_p_align, pagesize);
> -
> -  return new_p_align;
> +  return p_align >> 1;
>  }

Fixed.

I sent out the v9 patch.

> The rest looks ok.
>
> > 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..cdb453e696
> > --- /dev/null
> > +++ b/elf/tst-p_alignmod1-edit.c
> > @@ -0,0 +1,34 @@
> > +/* 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)
> > +{
> > +  size_t pagesize = sysconf (_SC_PAGESIZE);
> > +  size_t new_p_align = p_align >> 1;
> > +
> > +  if (new_p_align >= pagesize)
> > +    error (1, 0, "%s: new p_align (0x%zx) >= page size (0x%zx)",
> > +        file_name, new_p_align, pagesize);
> > +
> > +  return new_p_align;
> > +}



-- 
H.J.