perf build: Add ability to build with a generated vmlinux.h

Commit a887466562b4 ("perf bpf skels: Stop using vmlinux.h generated
from BTF, use subset of used structs + CO-RE") made it so that
vmlinux.h was uncondtionally included from
tools/perf/util/vmlinux.h. This change reverts part of that change (so
that vmlinux.h is once again generated) and makes it so that the
vmlinux.h used at build time is selected from the VMLINUX_H
variable. By default the VMLINUX_H variable is set to the vmlinux.h
added in change a887466562b4, but if GEN_VMLINUX_H=1 is passed on the
build command line then the previous generation behavior kicks in.

The build with GEN_VMLINUX_H=1 currently fails with:

    util/bpf_skel/lock_contention.bpf.c:419:8: error: redefinition of 'rq'
    struct rq {};
           ^
    /tmp/perf/util/bpf_skel/.tmp/../vmlinux.h:45630:8: note: previous definition is here
    struct rq {
           ^
    1 error generated.

Signed-off-by: Ian Rogers <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: James Clark <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Yang Jihong <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Tiezhu Yang <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
[ Format the error message and add a comment for GEN_VMLINUX_H ]
Signed-off-by: Namhyung Kim <[email protected]>

0 files changed, 0 insertions, 0 deletions