[PATCH] tools/perf: Fix bpf__probe to set bpf_prog_type type only if differs from the desired one

Athira Rajeev atrajeev at linux.vnet.ibm.com
Mon Aug 7 14:52:23 AEST 2023

The test "BPF prologue generation" fails as below:

   Writing event: p:perf_bpf_probe/func _text+10423200 f_mode=+20(%gpr3):x32 offset=%gpr4:s64 orig=%gpr5:s32
   In map_prologue, ntevs=1
   libbpf: prog 'bpf_func__null_lseek': BPF program load failed: Permission denied
   libbpf: prog 'bpf_func__null_lseek': -- BEGIN PROG LOAD LOG --
   btf_vmlinux is malformed
   reg type unsupported for arg#0 function bpf_func__null_lseek#5
   0: R1=ctx(off=0,imm=0) R10=fp0
   0: (57) r3 &= 2
   R3 !read_ok
   processed 1 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
   libbpf: prog 'bpf_func__null_lseek': failed to load: -13
   libbpf: failed to load object '[bpf_prologue_test]'
   bpf: load objects failed: err=-13: (Permission denied)
   Failed to add events selected by BPF

This fails occurs after this commit:
commit d6e6286a12e7 ("libbpf: disassociate section handler
on explicit bpf_program__set_type() call")'

With this change, SEC_DEF handler libbpf which is determined
initially based on program's SEC() is set to NULL. The change
is made because sec_def is not valid when user sets the program
type with bpf_program__set_type function. This commit also fixed
bpf_prog_test_load() helper in selftests/bpf to force-set program
type only if it differs from the desired one.

The "bpf__probe" function in util/bpf-loader.c, also calls
bpf_program__set_type to set bpf_prog_type. Add similar fix in
here as well to avoid setting sec_def to NULL.

Reported-by: Sachin Sant <sachinp at linux.vnet.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
 tools/perf/util/bpf-loader.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 44cde27d6389..b8e0b430e302 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -870,12 +870,14 @@ int bpf__probe(struct bpf_object *obj)
 			goto out;
-		if (priv->is_tp) {
+		if (priv->is_tp && bpf_program__type(prog) != BPF_PROG_TYPE_TRACEPOINT) {
 			bpf_program__set_type(prog, BPF_PROG_TYPE_TRACEPOINT);
-		bpf_program__set_type(prog, BPF_PROG_TYPE_KPROBE);
+		if (bpf_program__type(prog) != BPF_PROG_TYPE_KPROBE)
+			bpf_program__set_type(prog, BPF_PROG_TYPE_KPROBE);
 		pev = &priv->pev;
 		err = convert_perf_probe_events(pev, 1);

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