From e83b9f55448afce3fe1abcd1d10db9584f8042a6 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Tue, 2 Apr 2019 09:49:50 -0700 Subject: kbuild: add ability to generate BTF type info for vmlinux This patch adds new config option to trigger generation of BTF type information from DWARF debuginfo for vmlinux and kernel modules through pahole, which in turn relies on libbpf for btf_dedup() algorithm. The intent is to record compact type information of all types used inside kernel, including all the structs/unions/typedefs/etc. This enables BPF's compile-once-run-everywhere ([0]) approach, in which tracing programs that are inspecting kernel's internal data (e.g., struct task_struct) can be compiled on a system running some kernel version, but would be possible to run on other kernel versions (and configurations) without recompilation, even if the layout of structs changed and/or some of the fields were added, removed, or renamed. This is only possible if BPF loader can get kernel type info to adjust all the offsets correctly. This patch is a first time in this direction, making sure that BTF type info is part of Linux kernel image in non-loadable ELF section. BTF deduplication ([1]) algorithm typically provides 100x savings compared to DWARF data, so resulting .BTF section is not big as is typically about 2MB in size. [0] http://vger.kernel.org/lpc-bpf2018.html#session-2 [1] https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html Cc: Masahiro Yamada Cc: Arnaldo Carvalho de Melo Cc: Daniel Borkmann Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Martin KaFai Lau Signed-off-by: Andrii Nakryiko Acked-by: David S. Miller Acked-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: Daniel Borkmann --- scripts/link-vmlinux.sh | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'scripts') diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index dc0e8c5a1402..dd2b31ccca6a 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -35,7 +35,7 @@ set -e info() { if [ "${quiet}" != "silent_" ]; then - printf " %-7s %s\n" ${1} ${2} + printf " %-7s %s\n" "${1}" "${2}" fi } @@ -91,6 +91,20 @@ vmlinux_link() fi } +# generate .BTF typeinfo from DWARF debuginfo +gen_btf() +{ + local pahole_ver; + + pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/') + if [ "${pahole_ver}" -lt "113" ]; then + info "BTF" "${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13" + exit 0 + fi + + info "BTF" ${1} + LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} +} # Create ${2} .o file with all symbols from the ${1} object file kallsyms() @@ -248,6 +262,10 @@ fi info LD vmlinux vmlinux_link "${kallsymso}" vmlinux +if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then + gen_btf vmlinux +fi + if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then info SORTEX vmlinux sortextable vmlinux -- cgit v1.2.3-59-g8ed1b From 68e5ab1fc8bd9c17ed94ac172ffe0b9b7e85a59a Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Mon, 15 Apr 2019 14:58:39 -0700 Subject: kbuild: handle old pahole more gracefully when generating BTF When CONFIG_DEBUG_INFO_BTF is enabled but available version of pahole is too old to support BTF generation, build script is supposed to emit warning and proceed with the build. Due to using exit instead of return from BASH function, existing handling code prematurely exits exit code 0, not completing some of the build steps. This patch fixes issue by correctly returning just from gen_btf() function only. Fixes: e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux") Cc: Masahiro Yamada Cc: Arnaldo Carvalho de Melo Cc: Daniel Borkmann Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Martin KaFai Lau Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Daniel Borkmann --- scripts/link-vmlinux.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'scripts') diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index dd2b31ccca6a..6a148d0d51bf 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -99,7 +99,7 @@ gen_btf() pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/') if [ "${pahole_ver}" -lt "113" ]; then info "BTF" "${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13" - exit 0 + return 0 fi info "BTF" ${1} -- cgit v1.2.3-59-g8ed1b From 581b31c36cfc58df603c415ab6f3c795611c0ca1 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sun, 5 May 2019 17:10:33 -0700 Subject: kbuild: tolerate missing pahole when generating BTF When BTF generation is enabled through CONFIG_DEBUG_INFO_BTF, scripts/link-vmlinux.sh detects if pahole version is too old and gracefully continues build process, skipping BTF generation build step. But if pahole is not available, build will still fail. This patch adds check for whether pahole exists at all and bails out gracefully, if not. Cc: Alexei Starovoitov Reported-by: Yonghong Song Fixes: e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann --- scripts/link-vmlinux.sh | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'scripts') diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 6a148d0d51bf..e3c06b9482a2 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -96,6 +96,11 @@ gen_btf() { local pahole_ver; + if ! [ -x "$(command -v ${PAHOLE})" ]; then + info "BTF" "${1}: pahole (${PAHOLE}) is not available" + return 0 + fi + pahole_ver=$(${PAHOLE} --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/') if [ "${pahole_ver}" -lt "113" ]; then info "BTF" "${1}: pahole version $(${PAHOLE} --version) is too old, need at least v1.13" -- cgit v1.2.3-59-g8ed1b