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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Stanislav Fomichev <sdf@google.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Sasha Levin <sashal@kernel.org>,
	linux-kbuild@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org
Subject: [PATCH AUTOSEL 5.4 179/205] bpf: Support pre-2.25-binutils objcopy for vmlinux BTF
Date: Thu, 16 Jan 2020 11:42:34 -0500
Message-ID: <20200116164300.6705-179-sashal@kernel.org> (raw)
In-Reply-To: <20200116164300.6705-1-sashal@kernel.org>

From: Stanislav Fomichev <sdf@google.com>

[ Upstream commit da5fb18225b49b97bb37c51bcbbb2990a507c364 ]

If vmlinux BTF generation fails, but CONFIG_DEBUG_INFO_BTF is set,
.BTF section of vmlinux is empty and kernel will prohibit
BPF loading and return "in-kernel BTF is malformed".

--dump-section argument to binutils' objcopy was added in version 2.25.
When using pre-2.25 binutils, BTF generation silently fails. Convert
to --only-section which is present on pre-2.25 binutils.

Documentation/process/changes.rst states that binutils 2.21+
is supported, not sure those standards apply to BPF subsystem.

v2:
* exit and print an error if gen_btf fails (John Fastabend)

v3:
* resend with Andrii's Acked-by/Tested-by tags

Fixes: 341dfcf8d78ea ("btf: expose BTF info through sysfs")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20191127161410.57327-1-sdf@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 scripts/link-vmlinux.sh | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 06495379fcd8..2998ddb323e3 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -127,7 +127,8 @@ gen_btf()
 		cut -d, -f1 | cut -d' ' -f2)
 	bin_format=$(LANG=C ${OBJDUMP} -f ${1} | grep 'file format' | \
 		awk '{print $4}')
-	${OBJCOPY} --dump-section .BTF=.btf.vmlinux.bin ${1} 2>/dev/null
+	${OBJCOPY} --set-section-flags .BTF=alloc -O binary \
+		--only-section=.BTF ${1} .btf.vmlinux.bin 2>/dev/null
 	${OBJCOPY} -I binary -O ${bin_format} -B ${bin_arch} \
 		--rename-section .data=.BTF .btf.vmlinux.bin ${2}
 }
@@ -253,6 +254,10 @@ btf_vmlinux_bin_o=""
 if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
 	if gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then
 		btf_vmlinux_bin_o=.btf.vmlinux.bin.o
+	else
+		echo >&2 "Failed to generate BTF for vmlinux"
+		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
+		exit 1
 	fi
 fi
 
-- 
2.20.1


  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200116164300.6705-1-sashal@kernel.org>
2020-01-16 16:40 ` [PATCH AUTOSEL 5.4 049/205] net: netsec: Correct dma sync for XDP_TX frames Sasha Levin
2020-01-16 16:40 ` [PATCH AUTOSEL 5.4 077/205] libbpf: Fix compatibility for kernels without need_wakeup Sasha Levin
2020-01-16 16:40 ` [PATCH AUTOSEL 5.4 080/205] libbpf: Don't use kernel-side u32 type in xsk.c Sasha Levin
2020-01-16 16:41 ` [PATCH AUTOSEL 5.4 111/205] libbpf: Fix memory leak/double free issue Sasha Levin
2020-01-16 16:41 ` [PATCH AUTOSEL 5.4 112/205] libbpf: Fix potential overflow issue Sasha Levin
2020-01-16 16:41 ` [PATCH AUTOSEL 5.4 113/205] libbpf: Fix another potential overflow issue in bpf_prog_linfo Sasha Levin
2020-01-16 16:41 ` [PATCH AUTOSEL 5.4 114/205] libbpf: Make btf__resolve_size logic always check size error condition Sasha Levin
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 155/205] libbpf: Fix call relocation offset calculation bug Sasha Levin
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 164/205] bpf: skmsg, fix potential psock NULL pointer dereference Sasha Levin
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 172/205] xdp: Fix cleanup on map free for devmap_hash map type Sasha Levin
2020-01-16 16:42 ` Sasha Levin [this message]
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 180/205] libbpf: Fix Makefile' libbpf symbol mismatch diagnostic Sasha Levin
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 186/205] bpf: Force .BTF section start to zero when dumping from vmlinux Sasha Levin
2020-01-16 16:42 ` [PATCH AUTOSEL 5.4 191/205] samples/bpf: Fix broken xdp_rxq_info due to map order assumptions Sasha Levin

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