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