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From 9783e8b3de077c2e6399a9aa83f93237690bd744 Mon Sep 17 00:00:00 2001
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From: Andrea Claudi <aclaudi@redhat.com>
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Date: Thu, 13 Jun 2019 14:37:57 +0200
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Subject: [PATCH] bpf: check map symbol type properly with newer llvm compiler
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1716361
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Upstream Status: iproute2.git commit 7a04dd84a7f93
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commit 7a04dd84a7f938f72fcef9efe8383314b0a66274
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Author: Yonghong Song <yhs@fb.com>
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Date: Mon Oct 29 15:32:03 2018 -0700
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bpf: check map symbol type properly with newer llvm compiler
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With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE.
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-bash-4.4$ cat t.c
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__attribute__((section("maps"))) int g;
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-bash-4.4$ clang -target bpf -O2 -c t.c
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-bash-4.4$ readelf -s t.o
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Symbol table '.symtab' contains 2 entries:
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Num: Value Size Type Bind Vis Ndx Name
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0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
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1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g
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The following llvm commit enables BPF target to generate
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proper symbol type and size.
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commit bf6ec206615b9718869d48b4e5400d0c6e3638dd
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Author: Yonghong Song <yhs@fb.com>
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Date: Wed Sep 19 16:04:13 2018 +0000
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[bpf] Symbol sizes and types in object file
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Clang-compiled object files currently don't include the symbol sizes and
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types. Some tools however need that information. For example, ctfconvert
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uses that information to generate FreeBSD's CTF representation from ELF
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files.
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With this patch, symbol sizes and types are included in object files.
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Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
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Reported-by: Yutaro Hayakawa <yhayakawa3720@gmail.com>
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Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but OBJECT.
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-bash-4.4$ clang -target bpf -O2 -c t.c
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-bash-4.4$ readelf -s t.o
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Symbol table '.symtab' contains 3 entries:
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Num: Value Size Type Bind Vis Ndx Name
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0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
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1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c
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2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g
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This patch makes sure bpf library accepts both NOTYPE and OBJECT types
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of global map symbols.
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Signed-off-by: Yonghong Song <yhs@fb.com>
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Acked-by: Daniel Borkmann <daniel@iogearbox.net>
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Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
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---
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lib/bpf.c | 12 +++++++++---
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1 file changed, 9 insertions(+), 3 deletions(-)
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diff --git a/lib/bpf.c b/lib/bpf.c
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index d093d0bd86eae..45f279fa4a416 100644
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--- a/lib/bpf.c
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+++ b/lib/bpf.c
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@@ -1758,11 +1758,13 @@ static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which)
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int i;
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for (i = 0; i < ctx->sym_num; i++) {
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+ int type = GELF_ST_TYPE(sym.st_info);
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+
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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- GELF_ST_TYPE(sym.st_info) != STT_NOTYPE ||
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+ (type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps ||
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sym.st_value / ctx->map_len != which)
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continue;
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@@ -1849,11 +1851,13 @@ static int bpf_map_num_sym(struct bpf_elf_ctx *ctx)
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GElf_Sym sym;
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for (i = 0; i < ctx->sym_num; i++) {
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+ int type = GELF_ST_TYPE(sym.st_info);
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+
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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- GELF_ST_TYPE(sym.st_info) != STT_NOTYPE ||
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+ (type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps)
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continue;
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num++;
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@@ -1927,10 +1931,12 @@ static int bpf_map_verify_all_offs(struct bpf_elf_ctx *ctx, int end)
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* the table again.
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*/
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for (i = 0; i < ctx->sym_num; i++) {
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+ int type = GELF_ST_TYPE(sym.st_info);
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+
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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- GELF_ST_TYPE(sym.st_info) != STT_NOTYPE ||
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+ (type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps)
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continue;
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if (sym.st_value == off)
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--
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2.20.1
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