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Re: Buildbot failure in Wildebeest Builder on whole buildset
On Tue, 2018-11-13 at 18:29 +0100, Mark Wielaard wrote:
> So we might actually have two bugs. 1) we don't handle incorrectly
> aligned compressed sections and 2) we generate such incorrectly
> aligned compressed sections ourselves.
>
> Pondering fixes.
The fixes were easy!
(Hopefully the buildbot agrees.)
I pushed the attached.
Cheers,
Mark
From cf10453f8252df81225796d98548ba6eac113df3 Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mark@klomp.org>
Date: Tue, 13 Nov 2018 21:18:09 +0100
Subject: [PATCH] libelf: Correctly setup alignment of SHF_COMPRESSED section
data.
We didn't set the alignment of SHF_COMPRESSED sections correctly.
Those sections start with an Elf(32|64)_Chdr. Make sure sh_addralign
is setup to be able to read such a struct directly. Likewise don't
trust the alignment set on any SHF_COMPRESSED section, but always
make the (raw) compressed data aligned correctly for the reading the
Elf(32|64)_Chdr directly.
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libelf/ChangeLog | 7 +++++++
libelf/elf_compress.c | 4 ++--
libelf/elf_getdata.c | 10 ++++++++--
3 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index ab078cb..93820d1 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,10 @@
+2018-11-13 Mark Wielaard <mark@klomp.org>
+
+ * elf_getdata.c (__libelf_set_rawdata_wrlock): Explicitly set the
+ alignment of SHF_COMPRESSED data to the alignment of ELF_T_CHDR.
+ * elf_compress.c (elf_compress): After compression set sh_addralign
+ to the alignment of ELF_T_CHDR.
+
2018-11-09 Mark Wielaard <mark@klomp.org>
* elf_compress_gnu.c (elf_compress_gnu): Use elf_getdata.
diff --git a/libelf/elf_compress.c b/libelf/elf_compress.c
index d96245d..be9eeab 100644
--- a/libelf/elf_compress.c
+++ b/libelf/elf_compress.c
@@ -455,14 +455,14 @@ elf_compress (Elf_Scn *scn, int type, unsigned int flags)
{
Elf32_Shdr *shdr = elf32_getshdr (scn);
shdr->sh_size = new_size;
- shdr->sh_addralign = 1;
+ shdr->sh_addralign = __libelf_type_align (ELFCLASS32, ELF_T_CHDR);
shdr->sh_flags |= SHF_COMPRESSED;
}
else
{
Elf64_Shdr *shdr = elf64_getshdr (scn);
shdr->sh_size = new_size;
- shdr->sh_addralign = 1;
+ shdr->sh_addralign = __libelf_type_align (ELFCLASS64, ELF_T_CHDR);
shdr->sh_flags |= SHF_COMPRESSED;
}
diff --git a/libelf/elf_getdata.c b/libelf/elf_getdata.c
index 2043bba..639a798 100644
--- a/libelf/elf_getdata.c
+++ b/libelf/elf_getdata.c
@@ -268,9 +268,15 @@ __libelf_set_rawdata_wrlock (Elf_Scn *scn)
/* First a test whether the section is valid at all. */
size_t entsize;
- /* Compressed data has a header, but then compressed data. */
+ /* Compressed data has a header, but then compressed data.
+ Make sure to set the alignment of the header explicitly,
+ don't trust the file alignment for the section, it is
+ often wrong. */
if ((flags & SHF_COMPRESSED) != 0)
- entsize = 1;
+ {
+ entsize = 1;
+ align = __libelf_type_align (elf->class, ELF_T_CHDR);
+ }
else if (type == SHT_HASH)
{
GElf_Ehdr ehdr_mem;
--
1.8.3.1