From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66892C00454 for ; Tue, 10 Dec 2019 21:15:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32452206EC for ; Tue, 10 Dec 2019 21:15:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576012505; bh=RH4Oi4KY2cBvtGs8sL4JvqF5q9DMTHE4jUZynnxH8Sc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YaItdqlgVvfpr25EYRpvSqbGHHBc1K0RwlslaXS2cRIhlrTB8AmPQZomFcjyBERIB WWMaO6dJJ9asE1XGM7h72FY0kmq6gw54W1bZSYefGjIyGjmdbjI7Ep+KAd9UvQC0Sa UMekl/tRcLA2NfUfoGnopZpt3iK6uo9nvzLrwrkQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729424AbfLJVNp (ORCPT ); Tue, 10 Dec 2019 16:13:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:39814 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729344AbfLJVNb (ORCPT ); Tue, 10 Dec 2019 16:13:31 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0993D2077B; Tue, 10 Dec 2019 21:13:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576012409; bh=RH4Oi4KY2cBvtGs8sL4JvqF5q9DMTHE4jUZynnxH8Sc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zQOyTGVXxW5CUEZCBeR/CFi2sw9BBijmXAumI4+ERl1z+x4XCTt+tWun6vTRdXtJh gr4meJzW1UUMaKkZHloDMBZQ76vULq5rieZFVHOsLW4V7TWsKq+MVtrdJ/AhmW1Suf nleberJ0n+vV6ColGLGUt1T3McYUjyWtxqrWXYXA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrii Nakryiko , Alexei Starovoitov , Yonghong Song , Sasha Levin , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 327/350] libbpf: Fix call relocation offset calculation bug Date: Tue, 10 Dec 2019 16:07:12 -0500 Message-Id: <20191210210735.9077-288-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191210210735.9077-1-sashal@kernel.org> References: <20191210210735.9077-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrii Nakryiko [ Upstream commit a0d7da26ce86a25e97ae191cb90574ada6daea98 ] When relocating subprogram call, libbpf doesn't take into account relo->text_off, which comes from symbol's value. This generally works fine for subprograms implemented as static functions, but breaks for global functions. Taking a simplified test_pkt_access.c as an example: __attribute__ ((noinline)) static int test_pkt_access_subprog1(volatile struct __sk_buff *skb) { return skb->len * 2; } __attribute__ ((noinline)) static int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb) { return skb->len + val; } SEC("classifier/test_pkt_access") int test_pkt_access(struct __sk_buff *skb) { if (test_pkt_access_subprog1(skb) != skb->len * 2) return TC_ACT_SHOT; if (test_pkt_access_subprog2(2, skb) != skb->len + 2) return TC_ACT_SHOT; return TC_ACT_UNSPEC; } When compiled, we get two relocations, pointing to '.text' symbol. .text has st_value set to 0 (it points to the beginning of .text section): 0000000000000008 000000050000000a R_BPF_64_32 0000000000000000 .text 0000000000000040 000000050000000a R_BPF_64_32 0000000000000000 .text test_pkt_access_subprog1 and test_pkt_access_subprog2 offsets (targets of two calls) are encoded within call instruction's imm32 part as -1 and 2, respectively: 0000000000000000 test_pkt_access_subprog1: 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) 1: 64 00 00 00 01 00 00 00 w0 <<= 1 2: 95 00 00 00 00 00 00 00 exit 0000000000000018 test_pkt_access_subprog2: 3: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) 4: 04 00 00 00 02 00 00 00 w0 += 2 5: 95 00 00 00 00 00 00 00 exit 0000000000000000 test_pkt_access: 0: bf 16 00 00 00 00 00 00 r6 = r1 ===> 1: 85 10 00 00 ff ff ff ff call -1 2: bc 01 00 00 00 00 00 00 w1 = w0 3: b4 00 00 00 02 00 00 00 w0 = 2 4: 61 62 00 00 00 00 00 00 r2 = *(u32 *)(r6 + 0) 5: 64 02 00 00 01 00 00 00 w2 <<= 1 6: 5e 21 08 00 00 00 00 00 if w1 != w2 goto +8 7: bf 61 00 00 00 00 00 00 r1 = r6 ===> 8: 85 10 00 00 02 00 00 00 call 2 9: bc 01 00 00 00 00 00 00 w1 = w0 10: 61 62 00 00 00 00 00 00 r2 = *(u32 *)(r6 + 0) 11: 04 02 00 00 02 00 00 00 w2 += 2 12: b4 00 00 00 ff ff ff ff w0 = -1 13: 1e 21 01 00 00 00 00 00 if w1 == w2 goto +1 14: b4 00 00 00 02 00 00 00 w0 = 2 0000000000000078 LBB0_3: 15: 95 00 00 00 00 00 00 00 exit Now, if we compile example with global functions, the setup changes. Relocations are now against specifically test_pkt_access_subprog1 and test_pkt_access_subprog2 symbols, with test_pkt_access_subprog2 pointing 24 bytes into its respective section (.text), i.e., 3 instructions in: 0000000000000008 000000070000000a R_BPF_64_32 0000000000000000 test_pkt_access_subprog1 0000000000000048 000000080000000a R_BPF_64_32 0000000000000018 test_pkt_access_subprog2 Calls instructions now encode offsets relative to function symbols and are both set ot -1: 0000000000000000 test_pkt_access_subprog1: 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) 1: 64 00 00 00 01 00 00 00 w0 <<= 1 2: 95 00 00 00 00 00 00 00 exit 0000000000000018 test_pkt_access_subprog2: 3: 61 20 00 00 00 00 00 00 r0 = *(u32 *)(r2 + 0) 4: 0c 10 00 00 00 00 00 00 w0 += w1 5: 95 00 00 00 00 00 00 00 exit 0000000000000000 test_pkt_access: 0: bf 16 00 00 00 00 00 00 r6 = r1 ===> 1: 85 10 00 00 ff ff ff ff call -1 2: bc 01 00 00 00 00 00 00 w1 = w0 3: b4 00 00 00 02 00 00 00 w0 = 2 4: 61 62 00 00 00 00 00 00 r2 = *(u32 *)(r6 + 0) 5: 64 02 00 00 01 00 00 00 w2 <<= 1 6: 5e 21 09 00 00 00 00 00 if w1 != w2 goto +9 7: b4 01 00 00 02 00 00 00 w1 = 2 8: bf 62 00 00 00 00 00 00 r2 = r6 ===> 9: 85 10 00 00 ff ff ff ff call -1 10: bc 01 00 00 00 00 00 00 w1 = w0 11: 61 62 00 00 00 00 00 00 r2 = *(u32 *)(r6 + 0) 12: 04 02 00 00 02 00 00 00 w2 += 2 13: b4 00 00 00 ff ff ff ff w0 = -1 14: 1e 21 01 00 00 00 00 00 if w1 == w2 goto +1 15: b4 00 00 00 02 00 00 00 w0 = 2 0000000000000080 LBB2_3: 16: 95 00 00 00 00 00 00 00 exit Thus the right formula to calculate target call offset after relocation should take into account relocation's target symbol value (offset within section), call instruction's imm32 offset, and (subtracting, to get relative instruction offset) instruction index of call instruction itself. All that is shifted by number of instructions in main program, given all sub-programs are copied over after main program. Convert few selftests relying on bpf-to-bpf calls to use global functions instead of static ones. Fixes: 48cca7e44f9f ("libbpf: add support for bpf_call") Reported-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20191119224447.3781271-1-andriin@fb.com Signed-off-by: Sasha Levin --- tools/lib/bpf/libbpf.c | 8 ++++++-- tools/testing/selftests/bpf/progs/test_btf_haskv.c | 4 ++-- tools/testing/selftests/bpf/progs/test_btf_newkv.c | 4 ++-- tools/testing/selftests/bpf/progs/test_btf_nokv.c | 4 ++-- 4 files changed, 12 insertions(+), 8 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index a267cd0c0ce28..6a87ff9936d7b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1791,9 +1791,13 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr, pr_warning("incorrect bpf_call opcode\n"); return -LIBBPF_ERRNO__RELOC; } + if (sym.st_value % 8) { + pr_warn("bad call relo offset: %lu\n", sym.st_value); + return -LIBBPF_ERRNO__RELOC; + } prog->reloc_desc[i].type = RELO_CALL; prog->reloc_desc[i].insn_idx = insn_idx; - prog->reloc_desc[i].text_off = sym.st_value; + prog->reloc_desc[i].text_off = sym.st_value / 8; obj->has_pseudo_calls = true; continue; } @@ -3239,7 +3243,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj, prog->section_name); } insn = &prog->insns[relo->insn_idx]; - insn->imm += prog->main_prog_cnt - relo->insn_idx; + insn->imm += relo->text_off + prog->main_prog_cnt - relo->insn_idx; return 0; } diff --git a/tools/testing/selftests/bpf/progs/test_btf_haskv.c b/tools/testing/selftests/bpf/progs/test_btf_haskv.c index e5c79fe0ffdb2..d65c61e64df2f 100644 --- a/tools/testing/selftests/bpf/progs/test_btf_haskv.c +++ b/tools/testing/selftests/bpf/progs/test_btf_haskv.c @@ -25,7 +25,7 @@ struct dummy_tracepoint_args { }; __attribute__((noinline)) -static int test_long_fname_2(struct dummy_tracepoint_args *arg) +int test_long_fname_2(struct dummy_tracepoint_args *arg) { struct ipv_counts *counts; int key = 0; @@ -43,7 +43,7 @@ static int test_long_fname_2(struct dummy_tracepoint_args *arg) } __attribute__((noinline)) -static int test_long_fname_1(struct dummy_tracepoint_args *arg) +int test_long_fname_1(struct dummy_tracepoint_args *arg) { return test_long_fname_2(arg); } diff --git a/tools/testing/selftests/bpf/progs/test_btf_newkv.c b/tools/testing/selftests/bpf/progs/test_btf_newkv.c index 5ee3622ddebb6..8e83317db841f 100644 --- a/tools/testing/selftests/bpf/progs/test_btf_newkv.c +++ b/tools/testing/selftests/bpf/progs/test_btf_newkv.c @@ -33,7 +33,7 @@ struct dummy_tracepoint_args { }; __attribute__((noinline)) -static int test_long_fname_2(struct dummy_tracepoint_args *arg) +int test_long_fname_2(struct dummy_tracepoint_args *arg) { struct ipv_counts *counts; int key = 0; @@ -56,7 +56,7 @@ static int test_long_fname_2(struct dummy_tracepoint_args *arg) } __attribute__((noinline)) -static int test_long_fname_1(struct dummy_tracepoint_args *arg) +int test_long_fname_1(struct dummy_tracepoint_args *arg) { return test_long_fname_2(arg); } diff --git a/tools/testing/selftests/bpf/progs/test_btf_nokv.c b/tools/testing/selftests/bpf/progs/test_btf_nokv.c index 434188c377743..3f44220447594 100644 --- a/tools/testing/selftests/bpf/progs/test_btf_nokv.c +++ b/tools/testing/selftests/bpf/progs/test_btf_nokv.c @@ -23,7 +23,7 @@ struct dummy_tracepoint_args { }; __attribute__((noinline)) -static int test_long_fname_2(struct dummy_tracepoint_args *arg) +int test_long_fname_2(struct dummy_tracepoint_args *arg) { struct ipv_counts *counts; int key = 0; @@ -41,7 +41,7 @@ static int test_long_fname_2(struct dummy_tracepoint_args *arg) } __attribute__((noinline)) -static int test_long_fname_1(struct dummy_tracepoint_args *arg) +int test_long_fname_1(struct dummy_tracepoint_args *arg) { return test_long_fname_2(arg); } -- 2.20.1