summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorAndrii Nakryiko <andriin@fb.com>2019-04-02 09:49:50 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2019-04-03 00:53:07 +0200
commite83b9f55448afce3fe1abcd1d10db9584f8042a6 (patch)
tree4a8ccfba6f274d3b7d4e61c0d11789d9bc0706bb
parent99182beed858a1bde22f60046602b9b223225f73 (diff)
downloadlinux-e83b9f55448afce3fe1abcd1d10db9584f8042a6.tar.gz
linux-e83b9f55448afce3fe1abcd1d10db9584f8042a6.tar.bz2
linux-e83b9f55448afce3fe1abcd1d10db9584f8042a6.zip
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 <yamada.masahiro@socionext.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Alexei Starovoitov <ast@fb.com> Cc: Yonghong Song <yhs@fb.com> Cc: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Andrii Nakryiko <andriin@fb.com> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
-rw-r--r--Makefile3
-rw-r--r--lib/Kconfig.debug8
-rwxr-xr-xscripts/link-vmlinux.sh20
3 files changed, 29 insertions, 2 deletions
diff --git a/Makefile b/Makefile
index c0a34064c574..73c013378559 100644
--- a/Makefile
+++ b/Makefile
@@ -399,6 +399,7 @@ NM = $(CROSS_COMPILE)nm
STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
+PAHOLE = pahole
LEX = flex
YACC = bison
AWK = awk
@@ -453,7 +454,7 @@ KBUILD_LDFLAGS :=
GCC_PLUGINS_CFLAGS :=
export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
-export CPP AR NM STRIP OBJCOPY OBJDUMP KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
+export CPP AR NM STRIP OBJCOPY OBJDUMP PAHOLE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
export MAKE LEX YACC AWK INSTALLKERNEL PERL PYTHON PYTHON2 PYTHON3 UTS_MACHINE
export HOSTCXX KBUILD_HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0d9e81779e37..188fc17c2202 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -219,6 +219,14 @@ config DEBUG_INFO_DWARF4
But it significantly improves the success of resolving
variables in gdb on optimized code.
+config DEBUG_INFO_BTF
+ bool "Generate BTF typeinfo"
+ depends on DEBUG_INFO
+ help
+ Generate deduplicated BTF type information from DWARF debug info.
+ Turning this on expects presence of pahole tool, which will convert
+ DWARF type info into equivalent deduplicated BTF type info.
+
config GDB_SCRIPTS
bool "Provide GDB scripts for kernel debugging"
depends on DEBUG_INFO
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index dc0e8c5a1402..dd2b31ccca6a 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -35,7 +35,7 @@ set -e
info()
{
if [ "${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