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Accepting request 896646 from home:michals

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- Handle zero sized per-cpu veriables in Linux BTF.
  + btf_encoder-fix-and-complete-filtering-out-zero-sized-per-CPU-variables.patch

OBS-URL: https://build.opensuse.org/request/show/896646
OBS-URL: https://build.opensuse.org/package/show/devel:tools/dwarves?expand=0&rev=65
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Jan Engelhardt 2021-06-01 10:55:47 +00:00 committed by Git OBS Bridge
parent f2236ad99a
commit 9aca74399e
3 changed files with 91 additions and 0 deletions
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84
btf_encoder-fix-and-complete-filtering-out-zero-sized-per-CPU-variables.patch Normal file
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@ -0,0 +1,84 @@
From 0d17503db0580a6635d103fed030724b38ba1364 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 24 May 2021 16:42:22 -0700
Subject: [PATCH] btf_encoder: fix and complete filtering out zero-sized
per-CPU variables
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Upstram: accepted - expected version 1.22
Git-commit: 0d17503db0580a6635d103fed030724b38ba1364
btf_encoder is ignoring zero-sized per-CPU ELF symbols, but the same has to be
done for DWARF variables when matching them with ELF symbols. This is due to
zero-sized DWARF variables matching unrelated (non-zero-sized) variable that
happens to be allocated at the exact same address, leading to a lot of
confusion in BTF.
See [0] for when this causes big problems.
[0] https://lore.kernel.org/bpf/CAEf4BzZ0-sihSL-UAm21JcaCCY92CqfNxycHRZYXcoj8OYb=wA@mail.gmail.com/
Committer notes:
Kept the {} around the if block with more than one line, which
simplifies the original patch by just removing that assignment
to the 'dwarf_name' variable.
Reported-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: bpf@vger.kernel.org
Cc: dwarves@vger.kernel.org
Cc: kernel-team@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
btf_encoder.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/btf_encoder.c b/btf_encoder.c
index c711f12..033c927 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -538,6 +538,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
cu__for_each_variable(cu, core_id, pos) {
uint32_t size, type, linkage;
const char *name, *dwarf_name;
+ const struct tag *tag;
uint64_t addr;
int id;
@@ -550,6 +551,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
/* addr has to be recorded before we follow spec */
addr = var->ip.addr;
+ dwarf_name = variable__name(var, cu);
/* DWARF takes into account .data..percpu section offset
* within its segment, which for vmlinux is 0, but for kernel
@@ -583,7 +585,6 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
* per-CPU symbols have non-zero values.
*/
if (var->ip.addr == 0) {
- dwarf_name = variable__name(var, cu);
if (!dwarf_name || strcmp(dwarf_name, name))
continue;
}
@@ -600,6 +601,13 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
break;
}
+ tag = cu__type(cu, var->ip.tag.type);
+ if (tag__size(tag, cu) == 0) {
+ if (btf_elf__verbose)
+ fprintf(stderr, "Ignoring zero-sized per-CPU variable '%s'...\n", dwarf_name ?: "<missing name>");
+ continue;
+ }
+
type = var->ip.tag.type + type_id_off;
linkage = var->external ? BTF_VAR_GLOBAL_ALLOCATED : BTF_VAR_STATIC;
--
2.31.1

6
dwarves.changes
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@ -1,3 +1,9 @@
-------------------------------------------------------------------
Tue Jun 1 10:28:25 UTC 2021 - Michal Suchanek <msuchanek@suse.com>
- Handle zero sized per-cpu veriables in Linux BTF.
+ btf_encoder-fix-and-complete-filtering-out-zero-sized-per-CPU-variables.patch
-------------------------------------------------------------------
Mon May 3 08:45:43 UTC 2021 - Jiri Slaby <jslaby@suse.cz>

1
dwarves.spec
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@ -29,6 +29,7 @@ Source: https://fedorapeople.org/~acme/dwarves/dwarves-%version.tar.xz
Source2: https://fedorapeople.org/~acme/dwarves/dwarves-%version.tar.sign
Source9: baselibs.conf
Patch0: remove-ftrace-filter.patch
Patch1: btf_encoder-fix-and-complete-filtering-out-zero-sized-per-CPU-variables.patch
BuildRequires: cmake
BuildRequires: libdw-devel >= 0.171
%if 0%{?suse_version} < 1550