From 83535cb2bfa0fabbb31dbcbc6ffe759a03757c0f Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 20 Nov 2019 23:07:43 -0800 Subject: [PATCH] libbpf: Support initialized global variables Initialized global variables are no different in ELF from static variables, and don't require any extra support from libbpf. But they are matching semantics of global data (backed by BPF maps) more closely, preventing LLVM/Clang from aggressively inlining constant values and not requiring volatile incantations to prevent those. This patch enables global variables. It still disables uninitialized variables, which will be put into special COM (common) ELF section, because BPF doesn't allow uninitialized data to be accessed. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20191121070743.1309473-5-andriin@fb.com --- src/libbpf.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/src/libbpf.c b/src/libbpf.c index 64bc75f..a4e250a 100644 --- a/src/libbpf.c +++ b/src/libbpf.c @@ -1835,8 +1835,8 @@ static int bpf_program__record_reloc(struct bpf_program *prog, return -LIBBPF_ERRNO__RELOC; } if (!shdr_idx || shdr_idx >= SHN_LORESERVE) { - pr_warn("relocation: not yet supported relo for non-static global \'%s\' variable in special section (0x%x) found in insns[%d].code 0x%x\n", - name, shdr_idx, insn_idx, insn->code); + pr_warn("invalid relo for \'%s\' in special section 0x%x; forgot to initialize global var?..\n", + name, shdr_idx); return -LIBBPF_ERRNO__RELOC; } @@ -1876,11 +1876,6 @@ static int bpf_program__record_reloc(struct bpf_program *prog, pr_warn("bad data relo against section %u\n", shdr_idx); return -LIBBPF_ERRNO__RELOC; } - if (GELF_ST_BIND(sym->st_info) == STB_GLOBAL) { - pr_warn("relocation: not yet supported relo for non-static global \'%s\' variable found in insns[%d].code 0x%x\n", - name, insn_idx, insn->code); - return -LIBBPF_ERRNO__RELOC; - } if (!obj->caps.global_data) { pr_warn("relocation: kernel does not support global \'%s\' variable access in insns[%d]\n", name, insn_idx);