Re: [PATCH] Also find CFI in sections of type SHT_X86_64_UNWIND
Hi Milian,
On Tue, 2018-11-06 at 00:12 +0100, Milian Wolff wrote:
> On Montag, 5. November 2018 00:04:32 CET Mark Wielaard wrote:
>
> Interestingly, when I try to reproduce this on my laptop (i.e. compile even
> the trivial C example), then I cannot reproduce this at all anymore - the
> .eh_frame sections show up as PROGBITS. My desktop at work still shows this
> behavior though (also see below). I can't quite explain this difference...
It seems to only happen with a specific combination of gcc and the gold
linker, I could only generate the SHT_X86_64_UNWIND sections only on
fedora 29 with gcc 8.2.1 and gold version 2.31.1-13.fc29 (1.16).
> > - It might be better to change the check to shdr->sh_type != SHT_NOBITS
> > The idea is probably that we don't want to look at the data in case
> > this is a .debug file which has it removed. This might be better than
> > adding a check for X86_64_UNWIND since then we would also need to
> > check the arch. Does != SHT_NOBITS work for you?
>
> Yes, since SHT_NOBITS is not equal to SHT_X86_64_UNWIND :)
OK, then lets change your patch to do that as attached.
> > - What does eu-readelf -S show?
> > I think we need a x86_64_section_type_name () ebl hook to show it
> > correctly.
>
> Yes, that looks like it:
And the other attached patch should clean that up.
Thanks,
Mark
From e556deeb6498b9a5fc320c1d9ee23c6fcdcab384 Mon Sep 17 00:00:00 2001
From: Milian Wolff
Date: Mon, 29 Oct 2018 16:21:26 +0100
Subject: [PATCH 1/2] Also find CFI in sections of type SHT_X86_64_UNWIND
On my system with g++ (GCC) 8.2.1 20180831 with GNU gold (GNU Binutils
2.31.1) 1.16, the .eh_frame section does not have type PROGBITS
but rather is using X86_64_UNWIND nowadays:
```
$ echo "int main(){ return 0; }" > test.c
$ gcc test.c
$ readelf --sections a.out | grep .eh_frame
[14] .eh_frame X86_64_UNWIND0670 0670
[15] .eh_frame_hdr X86_64_UNWIND0724 0724
```
Without this patch, libdw refuses to use the available unwind
information, leading to broken backtraces while unwinding. With the
patch applied, unwinding works once more in such situations.
Signed-off-by: Milian Wolff
Signed-off-by: Mark Wielaard
---
libdw/ChangeLog | 4
libdw/dwarf_getcfi_elf.c | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index ebe002c..627fdde 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,7 @@
+2018-10-29 Milian Wolff
+
+ * dwarf_getcfi_elf.c (getcfi_shdr): Check sh_type != SHT_NOBITS.
+
2018-09-13 Mark Wielaard
* dwarf_begin_elf.c (check_section): Drop ehdr argument, add and
diff --git a/libdw/dwarf_getcfi_elf.c b/libdw/dwarf_getcfi_elf.c
index 315cc02..adcaea0 100644
--- a/libdw/dwarf_getcfi_elf.c
+++ b/libdw/dwarf_getcfi_elf.c
@@ -298,7 +298,7 @@ getcfi_shdr (Elf *elf, const GElf_Ehdr *ehdr)
}
else if (!strcmp (name, ".eh_frame"))
{
- if (shdr->sh_type == SHT_PROGBITS)
+ if (shdr->sh_type != SHT_NOBITS)
return getcfi_scn_eh_frame (elf, ehdr, scn, shdr,
hdr_scn, hdr_vaddr);
else
--
1.8.3.1
From 3ca96596538cb57d9f23f6f5ddfc8e145e8b2177 Mon Sep 17 00:00:00 2001
From: Mark Wielaard
Date: Tue, 6 Nov 2018 12:01:25 +0100
Subject: [PATCH 2/2] backends: Add x86_64 section_type_name for
SHT_X86_64_UNWIND.
Makes sure that eu-readelf and eu-elflint recognize and show the
x86_64 specific section type correctly.
Signed-off-by: Mark Wielaard
---
backends/ChangeLog | 5 +
backends/x86_64_init.c | 3 ++-
backends/x86_64_symbol.c | 14 +-
3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/backends/ChangeLog b/backends/ChangeLog
index 768c270..e2a0281 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,3 +1,8 @@
+2018-11-06 Mark Wielaard
+
+ * x86_64_symbol.c (x86_64_section_type_name): New function.
+ * x86_64_init.c (x86_64_int): Hook section_type_name.
+
2018-10-20 Mark Wielaard
* ppc_initreg.c (ppc_set_initial_registers_tid): Use define instead of
diff --git a/backends/x86_64_init.c b/backends/x86_64_init.c
index adfa479..49f6c6c 100644
--- a/backends/x86_64_init.c
+++ b/backends/x86_64_init.c
@@ -1,5 +1,5 @@
/* Initialization of x86-64 specific backend library.
- Copyright (C) 2002-2009, 2013 Red Hat, Inc.
+ Copyright (C) 2002-2009, 2013, 2018 Red Hat, Inc.
Copyright (C) H.J. Lu , 2015.
This file is part of elfutils.
Written by Ulrich Drepper , 2002.
@@ -55,6 +55,7 @@ x86_64_init (Elf *elf __attribute__ ((unused)),
eh->name = "AMD x86-64";
x86_64_init_reloc (eh);
HOOK (eh, reloc_simple_type);
+ HOOK (eh, section_type_name);
if (eh->class == ELFCLASS32)
eh->core_note = x32_core_note;
else
diff --git a/backends/x86_64_symbol.c b/backends/x86_64_symbol.c
index e07b180..98457bc 100644
--- a/backends/x86_64_symbol.c
+++ b/backends/x86_64_symbol.c
@@ -1,5 +1,5 @@
/* x86_64 specific symbolic name handling.
Re: Add eu-strip --reloc-debug-sections-only option
On Fri, 2018-10-26 at 23:50 +0200, Mark Wielaard wrote: > eu-strip already supports --reloc-debug-sections to resolve all > relocations between .debug_ sections while creating a separate > .debug file with -f. It is sometimes useful to do the same without > doing any other stripping. > > --reloc-debug-sections-only > Similar to --reloc-debug-sections, but resolve all > trivial relocations between debug sections in > place. No other stripping is performed (operation > is not reversable, incompatible with -f, -g, > --remove-comment and --remove-section) > > For example to ease debugging, tracing and profiling some distributions > ship an uncompressed vmlinux ELF file which includes DWARF debuginfo. > Since the vmlinux ELF kernel is relocatable, the relocations between the > .debug sections are also still left in. On Fedora this file is 662M. > eu-strip --reloc-debug-sections-only will remove more than 250MB of > (unneeded) relocations between the .debug sections. > > To reuse as much code as possible this patch series first refactors > some of the code. It also makes it so that the type of ELF file doesn't > matter for doing relocations (normally it only makes sense for ET_REL > files, but the vmlinux ELF image is an ET_EXEC with SHT_RELA sections). > > It also adds a new testcase to run-strip-reloc.sh to make sure that the > result of creating a separate debug file using --reloc-debug-sections > is identical to creating a separate debug file and then running eu-strip > with --reloc-debug-sections-only. > > [PATCH 1/4] strip: Always copy over any phdrs if there are any > [PATCH 2/4] strip: Split out debug section relocation into separate helper > [PATCH 3/4] strip: Extract code to update shdrstrndx into new common function > [PATCH 4/4] strip: Add --reloc-debug-sections-only option I pushed these 4 patches to master. Cheers, Mark
Buildbot failure in Wildebeest Builder on whole buildset
The Buildbot has detected a failed build on builder whole buildset while building elfutils. Full details are available at: https://builder.wildebeest.org/buildbot/#builders/11/builds/244 Buildbot URL: https://builder.wildebeest.org/buildbot/ Worker for this Build: fedora-ppc64le Build Reason: Blamelist: Mark Wielaard BUILD FAILED: failed test (failure) Sincerely, -The BuildbotThe Buildbot has detected a failed build on builder whole buildset while building elfutils. Full details are available at: https://builder.wildebeest.org/buildbot/#builders/12/builds/242 Buildbot URL: https://builder.wildebeest.org/buildbot/ Worker for this Build: fedora-ppc64 Build Reason: Blamelist: Mark Wielaard BUILD FAILED: failed test (failure) Sincerely, -The BuildbotThe Buildbot has detected a failed build on builder whole buildset while building elfutils. Full details are available at: https://builder.wildebeest.org/buildbot/#builders/15/builds/81 Buildbot URL: https://builder.wildebeest.org/buildbot/ Worker for this Build: debian-armhf Build Reason: Blamelist: Mark Wielaard BUILD FAILED: failed test (failure) Sincerely, -The Buildbot
Re: [PATCH 4/4] strip: Add --reloc-debug-sections-only option.
On Fri, 2018-10-26 at 23:50 +0200, Mark Wielaard wrote:
> diff --git a/tests/ChangeLog b/tests/ChangeLog
> index 751a081..0870d4c 100644
> --- a/tests/ChangeLog
> +++ b/tests/ChangeLog
> @@ -1,3 +1,7 @@
> +2018-10-26 Mark Wielaard
> +
> + * run-strip-reloc.sh: Add a test for --reloc-debug-sections-only.
> +
> 2018-10-12 Mark Wielaard
>
> * run-readelf-zdebug.sh: Adjust flags output.
> diff --git a/tests/run-strip-reloc.sh b/tests/run-strip-reloc.sh
> index bbc9f58..6e54ab4 100755
> --- a/tests/run-strip-reloc.sh
> +++ b/tests/run-strip-reloc.sh
> @@ -32,6 +32,8 @@ runtest() {
>outfile2=out.stripped2
>debugfile2=out.debug2
>
> + echo "runtest $infile"
> +
>rm -f $outfile1 $debugfile1 $outfile2 $debugfile2
>
>testrun ${abs_top_builddir}/src/strip -o $outfile1 -f $debugfile1 $infile
> ||
> @@ -67,6 +69,15 @@ runtest() {
>
>testrun_compare cat readelf.out1 < readelf.out2 ||
>{ echo "*** failure readelf -w compare $infile"; status=1; }
> +
> + testrun ${abs_top_builddir}/src/strip --reloc-debug-sections-only \
> + $debugfile1 ||
> + { echo "*** failure strip --reloc-debug-sections-only $debugfile1"; \
> +status=1; }
> +
> + cmp $debugfile1 $debugfile2 ||
> + { echo "*** failure --reloc-debug-sections[-only] $debugfile1
> $debugfile2"; \
> +status=1; }
> }
>
> # Most simple hello world kernel module for various architectures.
The buildbot didn't sent any failure emails (I am still looking into
why), but this new cmp test failed on debian-armhf, fedora-ppc64 and
fedora-ppc64le:
https://builder.wildebeest.org/buildbot/#/builders/15/builds/81
https://builder.wildebeest.org/buildbot/#/builders/12/builds/242
https://builder.wildebeest.org/buildbot/#/builders/11/builds/244
It succeeds on everything else. Still investigating.
