Pass the value of make's -j/--jobs argument to pahole, to avoid out of
memory errors and make pahole respect the "jobs" value of make.
On systems with little memory but many cores, invoking pahole using -j
without argument potentially creates too many pahole instances,
causing an out-of-memory situation. Instead, we should pass make's
"jobs" value as an argument to pahole's -j, which is likely configured
to be (much) lower than the actual core count on such systems.
If make was invoked without -j, either via cmdline or MAKEFLAGS, then
JOBS will be simply empty, resulting in the existing behavior, as
expected.
Signed-off-by: Florian Schmaus <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Tested-by: Holger Hoffstätte <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Support creation of module BTF along with distilled base BTF;
the latter is stored in a .BTF.base ELF section and supplements
split BTF references to base BTF with information about base types,
allowing for later relocation of split BTF with a (possibly
changed) base. resolve_btfids detects the presence of a .BTF.base
section and will use it instead of the base BTF it is passed in
BTF id resolution.
Modules will be built with a distilled .BTF.base section for external
module build, i.e.
make -C. -M=path2/module
...while in-tree module build as part of a normal kernel build will
not generate distilled base BTF; this is because in-tree modules
change with the kernel and do not require BTF relocation for the
running vmlinux.
Signed-off-by: Alan Maguire <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Reviewed-by: Eduard Zingerman <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
There is no need to set the pahole v1.25-only flags in an
"ifeq" version clause; we are already in a <= v1.25 branch
of "ifeq", so that combined with a "test-ge" v1.25 ensures the
flags will be applied for v1.25 only.
Suggested-by: Masahiro Yamada <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
The btf_features list can be used for pahole v1.26 and later -
it is useful because if a feature is not yet implemented it will
not exit with a failure message. This will allow us to add feature
requests to the pahole options without having to check pahole versions
in future; if the version of pahole supports the feature it will be
added.
Signed-off-by: Alan Maguire <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Tested-by: Eduard Zingerman <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
scripts/pahole-flags.sh is executed so many times.
You can confirm it, as follows:
$ cat <<EOF >> scripts/pahole-flags.sh
> echo "scripts/pahole-flags.sh was executed" >&2
> EOF
$ make -s
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
scripts/pahole-flags.sh was executed
[ lots of repeated lines... ]
This scripts is executed more than 20 times during the kernel build
because PAHOLE_FLAGS is a recursively expanded variable and exported
to sub-processes.
With GNU Make >= 4.4, it is executed more than 60 times because
exported variables are also passed to other $(shell ) invocations.
Without careful coding, it is known to cause an exponential fork
explosion. [1]
The use of $(shell ) in an exported recursive variable is likely wrong
because $(shell ) is always evaluated due to the 'export' keyword, and
the evaluation can occur multiple times by the nature of recursive
variables.
Convert the shell script to a Makefile, which is included only when
CONFIG_DEBUG_INFO_BTF=y.
[1]: https://savannah.gnu.org/bugs/index.php?64746
Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Alan Maguire <[email protected]>
Tested-by: Alan Maguire <[email protected]>
Reviewed-by: Nicolas Schier <[email protected]>
Tested-by: Miguel Ojeda <[email protected]>
Acked-by: Miguel Ojeda <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Ihor Solodrai