From 4e0dcb220bd77a5ddf0f8956740281efbf1ead90 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 31 Oct 2018 20:25:22 +0100 Subject: [PATCH iproute2-next 1/2] bpf: data section support poc To: Stephen Hemminger Cc: netdev@vger.kernel.org, daniel@iogearbox.net Signed-off-by: Daniel Borkmann --- lib/bpf.c | 40 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-) diff --git a/lib/bpf.c b/lib/bpf.c index 45f279fa4a41..eb208275ebaa 100644 --- a/lib/bpf.c +++ b/lib/bpf.c @@ -1142,6 +1142,7 @@ struct bpf_elf_ctx { Elf_Data *sym_tab; Elf_Data *str_tab; Elf_Data *btf_data; + Elf_Data *glo_data; char obj_uid[64]; int obj_fd; int btf_fd; @@ -1157,6 +1158,7 @@ struct bpf_elf_ctx { int sec_maps; int sec_text; int sec_btf; + int sec_data; char license[ELF_MAX_LICENSE_LEN]; enum bpf_prog_type type; __u32 ifindex; @@ -2037,6 +2039,15 @@ static int bpf_fetch_text(struct bpf_elf_ctx *ctx, int section, return 0; } +static int bpf_fetch_data(struct bpf_elf_ctx *ctx, int section, + struct bpf_elf_sec_data *data) +{ + ctx->sec_data = section; + ctx->glo_data = data->sec_data; + ctx->sec_done[section] = true; + return 0; +} + static void bpf_btf_report(int fd, struct bpf_elf_ctx *ctx) { fprintf(stderr, "\nBTF debug data section \'.BTF\' %s%s (%d)!\n", @@ -2246,6 +2257,11 @@ static bool bpf_has_call_data(const struct bpf_elf_ctx *ctx) return ctx->sec_text; } +static bool bpf_has_glob_data(const struct bpf_elf_ctx *ctx) +{ + return ctx->sec_data; +} + static int bpf_fetch_ancillary(struct bpf_elf_ctx *ctx, bool check_text_sec) { struct bpf_elf_sec_data data; @@ -2267,6 +2283,9 @@ static int bpf_fetch_ancillary(struct bpf_elf_ctx *ctx, bool check_text_sec) !strcmp(data.sec_name, ".text") && check_text_sec) ret = bpf_fetch_text(ctx, i, &data); + else if (data.sec_hdr.sh_type == SHT_PROGBITS && + !strcmp(data.sec_name, ".data")) + ret = bpf_fetch_data(ctx, i, &data); else if (data.sec_hdr.sh_type == SHT_SYMTAB && !strcmp(data.sec_name, ".symtab")) ret = bpf_fetch_symtab(ctx, i, &data); @@ -2380,6 +2399,21 @@ static int bpf_apply_relo_map(struct bpf_elf_ctx *ctx, struct bpf_elf_prog *prog return 0; } +static int bpf_apply_relo_glob(struct bpf_elf_ctx *ctx, struct bpf_elf_prog *prog, + GElf_Rel *relo, GElf_Sym *sym, + struct bpf_relo_props *props) +{ + unsigned int insn_off = relo->r_offset / sizeof(struct bpf_insn); + int *data; + + if (insn_off >= prog->insns_num) + return -EINVAL; + + data = ctx->glo_data->d_buf + sym->st_value; + prog->insns[insn_off].imm = *data; + return 0; +} + static int bpf_apply_relo_call(struct bpf_elf_ctx *ctx, struct bpf_elf_prog *prog, GElf_Rel *relo, GElf_Sym *sym, struct bpf_relo_props *props) @@ -2434,10 +2468,12 @@ static int bpf_apply_relo_data(struct bpf_elf_ctx *ctx, if (sym.st_shndx == ctx->sec_maps) ret = bpf_apply_relo_map(ctx, prog, &relo, &sym, props); + else if (sym.st_shndx == ctx->sec_data) + ret = bpf_apply_relo_glob(ctx, prog, &relo, &sym, props); else if (sym.st_shndx == ctx->sec_text) ret = bpf_apply_relo_call(ctx, prog, &relo, &sym, props); else - fprintf(stderr, "ELF contains non-{map,call} related relo data in entry %u pointing to section %u! Compiler bug?!\n", + fprintf(stderr, "ELF contains non-{map,data,call} related relo data in entry %u pointing to section %u! Compiler bug?!\n", relo_ent, sym.st_shndx); if (ret < 0) return ret; @@ -2533,7 +2569,7 @@ static int bpf_fetch_prog_sec(struct bpf_elf_ctx *ctx, const char *section) return ret; } - if (bpf_has_map_data(ctx) || bpf_has_call_data(ctx)) + if (bpf_has_map_data(ctx) || bpf_has_call_data(ctx) || bpf_has_glob_data(ctx)) ret = bpf_fetch_prog_relo(ctx, section, &lderr, &sseen, &prog); if (ret < 0 && !lderr) ret = bpf_fetch_prog(ctx, section, &sseen); -- 2.19.1