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Re: [PATCH] elf: Properly compute offsets of desc and next note
On Fri, Nov 24, 2017 at 2:42 PM, Simon Marchi <simon.marchi@ericsson.com> wrote:
> On 2017-11-24 05:20 PM, H.J. Lu wrote:
>> On Fri, Nov 24, 2017 at 12:53 PM, Simon Marchi
>> <simon.marchi@ericsson.com> wrote:
>>> Hi,
>>>
>>> Pedro found that this patch caused the GDB test "gdb.base/auxv.exp" to
>>> consume memory until the machine becomes unresponsive. I was able to
>>> reproduce it too, so I chose to revert the patch, to reduce the risk
>>> of it happening on other developer's machines and buildbot builders.
>>>
>>> The test can be ran with:
>>>
>>> gdb/$ make check TESTS="gdb.base/auxv.exp"
>>>
>>> (It's a good idea to ctrl-C quickly enough :))
>>>
>>> After running the test once, I was able to reproduce the issue by starting
>>> GDB manually like this:
>>>
>>> gdb/$ ./gdb -ex "core /home/emaisin/build/binutils-gdb/gdb/testsuite/outputs/gdb.base/auxv/auxv.corefile"
>>>
>>> There is an infinite loop in elf_parse_notes, the pointer "p" never
>>> gets advanced.
>>>
>>
>> This patch fixes the problem for me. Please give it a try.
>>
>> Thanks.
>
> It works fine on my side, thanks.
>
Here is the patch against master branch. Please give it try.
Thanks.
--
H.J.
From 276da9b31bd6e3eb8d1dd814c867266f59f29093 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 24 Nov 2017 14:49:36 -0800
Subject: [PATCH] Re-apply "elf: Properly compute offsets of note descriptor
and next note"
CORE PT_NOTE segments may have p_align values of 0 or 1. gABI specifies
that PT_NOTE alignment should be aligned to 4 bytes for 32-bit objects
and to 8 bytes for 64-bit objects. If segment alignment is less than 4,
we use 4 byte alignment.
---
bfd/ChangeLog | 15 +++++++++++++++
bfd/elf.c | 31 +++++++++++++++++++++----------
binutils/ChangeLog | 7 +++++++
binutils/readelf.c | 8 ++++++--
include/ChangeLog | 7 +++++++
include/elf/external.h | 16 ++++++++++++++++
6 files changed, 72 insertions(+), 12 deletions(-)
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 55fe3b4e61..0395dcf6cc 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,18 @@
+2017-11-24 H.J. Lu <hongjiu.lu@intel.com>
+
+ PR binutils/22444
+ * elf.c (elf_read_notes): Add an argument for note aligment.
+ (elf_parse_notes): Likewise.
+ (_bfd_elf_make_section_from_shdr): Pass section aligment to
+ elf_parse_notes.
+ (bfd_section_from_phdr): Pass segment aligment to elf_read_notes.
+ (elf_parse_notes): Add an argument for note aligment. Use
+ ELF_NOTE_DESC_OFFSET to get the offset of the note descriptor.
+ Use ELF_NOTE_NEXT_OFFSET to get the offset of the next note
+ entry.
+ (elf_read_notes): Add an argument for note aligment and pass it
+ to elf_parse_notes.
+
2017-11-23 Alan Modra <amodra@gmail.com>
* elf32-hppa.c (pc_dynrelocs): Define.
diff --git a/bfd/elf.c b/bfd/elf.c
index 8cd67ad59b..8f6aa53b5c 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -52,9 +52,10 @@ static int elf_sort_sections (const void *, const void *);
static bfd_boolean assign_file_positions_except_relocs (bfd *, struct bfd_link_info *);
static bfd_boolean prep_headers (bfd *);
static bfd_boolean swap_out_syms (bfd *, struct elf_strtab_hash **, int) ;
-static bfd_boolean elf_read_notes (bfd *, file_ptr, bfd_size_type) ;
+static bfd_boolean elf_read_notes (bfd *, file_ptr, bfd_size_type,
+ size_t align) ;
static bfd_boolean elf_parse_notes (bfd *abfd, char *buf, size_t size,
- file_ptr offset);
+ file_ptr offset, size_t align);
/* Swap version information in and out. The version information is
currently size independent. If that ever changes, this code will
@@ -1089,7 +1090,8 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
if (!bfd_malloc_and_get_section (abfd, newsect, &contents))
return FALSE;
- elf_parse_notes (abfd, (char *) contents, hdr->sh_size, hdr->sh_offset);
+ elf_parse_notes (abfd, (char *) contents, hdr->sh_size,
+ hdr->sh_offset, hdr->sh_addralign);
free (contents);
}
@@ -2990,7 +2992,8 @@ bfd_section_from_phdr (bfd *abfd, Elf_Internal_Phdr *hdr, int hdr_index)
case PT_NOTE:
if (! _bfd_elf_make_section_from_phdr (abfd, hdr, hdr_index, "note"))
return FALSE;
- if (! elf_read_notes (abfd, hdr->p_offset, hdr->p_filesz))
+ if (! elf_read_notes (abfd, hdr->p_offset, hdr->p_filesz,
+ hdr->p_align))
return FALSE;
return TRUE;
@@ -10970,14 +10973,21 @@ elfcore_write_register_note (bfd *abfd,
}
static bfd_boolean
-elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset)
+elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset,
+ size_t align)
{
char *p;
+ /* NB: CORE PT_NOTE segments may have p_align values of 0 or 1.
+ gABI specifies that PT_NOTE alignment should be aligned to 4
+ bytes for 32-bit objects and to 8 bytes for 64-bit objects. If
+ align is less than 4, we use 4 byte alignment. */
+ if (align < 4)
+ align = 4;
+
p = buf;
while (p < buf + size)
{
- /* FIXME: bad alignment assumption. */
Elf_External_Note *xnp = (Elf_External_Note *) p;
Elf_Internal_Note in;
@@ -10992,7 +11002,7 @@ elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset)
return FALSE;
in.descsz = H_GET_32 (abfd, xnp->descsz);
- in.descdata = in.namedata + BFD_ALIGN (in.namesz, 4);
+ in.descdata = p + ELF_NOTE_DESC_OFFSET (in.namesz, align);
in.descpos = offset + (in.descdata - buf);
if (in.descsz != 0
&& (in.descdata >= buf + size
@@ -11054,14 +11064,15 @@ elf_parse_notes (bfd *abfd, char *buf, size_t size, file_ptr offset)
break;
}
- p = in.descdata + BFD_ALIGN (in.descsz, 4);
+ p += ELF_NOTE_NEXT_OFFSET (in.namesz, in.descsz, align);
}
return TRUE;
}
static bfd_boolean
-elf_read_notes (bfd *abfd, file_ptr offset, bfd_size_type size)
+elf_read_notes (bfd *abfd, file_ptr offset, bfd_size_type size,
+ size_t align)
{
char *buf;
@@ -11080,7 +11091,7 @@ elf_read_notes (bfd *abfd, file_ptr offset, bfd_size_type size)
buf[size] = 0;
if (bfd_bread (buf, size, abfd) != size
- || !elf_parse_notes (abfd, buf, size, offset))
+ || !elf_parse_notes (abfd, buf, size, offset, align))
{
free (buf);
return FALSE;
diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 32df4b98f7..eab683047e 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,10 @@
+2017-11-24 H.J. Lu <hongjiu.lu@intel.com>
+
+ PR binutils/22444
+ * readelf.c (process_notes_at): Use ELF_NOTE_DESC_OFFSET to get
+ the offset of the note descriptor. Use ELF_NOTE_NEXT_OFFSET to
+ get the offset of the next note entry.
+
2017-11-23 Pavel I. Kryukov <kryukov@frtk.ru>
PR 22485
diff --git a/binutils/readelf.c b/binutils/readelf.c
index 5944ebee96..739367d899 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -17969,9 +17969,13 @@ process_notes_at (Filedata * filedata,
inote.namesz = BYTE_GET (external->namesz);
inote.namedata = external->name;
inote.descsz = BYTE_GET (external->descsz);
- inote.descdata = inote.namedata + align_power (inote.namesz, 2);
+ inote.descdata = ((char *) external
+ + ELF_NOTE_DESC_OFFSET (inote.namesz,
+ section->sh_addralign));
inote.descpos = offset + (inote.descdata - (char *) pnotes);
- next = inote.descdata + align_power (inote.descsz, 2);
+ next = ((char *) external
+ + ELF_NOTE_NEXT_OFFSET (inote.namesz, inote.descsz,
+ section->sh_addralign));
}
else
{
diff --git a/include/ChangeLog b/include/ChangeLog
index 670456cece..a7668678f8 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,10 @@
+2017-11-24 H.J. Lu <hongjiu.lu@intel.com>
+
+ PR binutils/22444
+ * elf/external.h (ELF_ALIGN_UP): New.
+ (ELF_NOTE_DESC_OFFSET): Likewise.
+ (ELF_NOTE_NEXT_OFFSET): Likewise.
+
2017-11-16 Tamar Christina <tamar.christina@arm.com>
* opcode/aarch64.h: (AARCH64_FEATURE_F16_FML): New.
diff --git a/include/elf/external.h b/include/elf/external.h
index d65bae0b21..eb0a53a9a9 100644
--- a/include/elf/external.h
+++ b/include/elf/external.h
@@ -183,6 +183,22 @@ typedef struct {
char name[1]; /* Start of the name+desc data */
} Elf_External_Note;
+/* Align an address upward to a boundary, expressed as a number of bytes.
+ E.g. align to an 8-byte boundary with argument of 8. */
+#define ELF_ALIGN_UP(addr, boundary) \
+ (((bfd_vma) (addr) + ((boundary) - 1)) & ~ (bfd_vma) ((boundary) -1))
+
+/* Compute the offset of the note descriptor from size of note entry's
+ owner string and note alignment. */
+#define ELF_NOTE_DESC_OFFSET(namesz, align) \
+ ELF_ALIGN_UP (offsetof (Elf_External_Note, name) + (namesz), (align))
+
+/* Compute the offset of the next note entry from size of note entry's
+ owner string, size of the note descriptor and note alignment. */
+#define ELF_NOTE_NEXT_OFFSET(namesz, descsz, align) \
+ ELF_ALIGN_UP (ELF_NOTE_DESC_OFFSET ((namesz), (align)) + (descsz), \
+ (align))
+
/* Relocation Entries */
typedef struct {
unsigned char r_offset[4]; /* Location at which to apply the action */
--
2.14.3