bpf: Force uprobe bpf program to always return 0

JIRA: https://issues.redhat.com/browse/RHEL-85485

commit f505005
Author: Jiri Olsa <jolsa@kernel.org>
Date:   Fri Nov 8 14:45:33 2024 +0100

    bpf: Force uprobe bpf program to always return 0

    As suggested by Andrii make uprobe multi bpf programs to always return 0,
    so they can't force uprobe removal.

    Keeping the int return type for uprobe_prog_run, because it will be used
    in following session changes.

    Fixes: 89ae89f ("bpf: Add multi uprobe link")
    Suggested-by: Andrii Nakryiko <andrii@kernel.org>
    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Acked-by: Andrii Nakryiko <andrii@kernel.org>
    Link: https://lore.kernel.org/bpf/20241108134544.480660-3-jolsa@kernel.org

Signed-off-by: Viktor Malik <vmalik@redhat.com>

Author: viktormalik

kernel/trace/bpf_trace.c

@@ -3208,7 +3208,6 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
 	struct bpf_prog *prog = link->link.prog;
 	bool sleepable = prog->sleepable;
 	struct bpf_run_ctx *old_run_ctx;
-	int err = 0;
 
 	if (link->task && !same_thread_group(current, link->task))
 		return 0;
@@ -3221,7 +3220,7 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
 	migrate_disable();
 
 	old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
-	err = bpf_prog_run(link->link.prog, regs);
+	bpf_prog_run(link->link.prog, regs);
 	bpf_reset_run_ctx(old_run_ctx);
 
 	migrate_enable();
@@ -3230,7 +3229,7 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
 		rcu_read_unlock_trace();
 	else
 		rcu_read_unlock();
-	return err;
+	return 0;
 }
 
 static bool