samples/bpf: fix symbol mismatch by compiler optimization

Currently, multiple kprobe programs are suffering from symbol mismatch
due to compiler optimization. These optimizations might induce
additional suffix to the symbol name such as '.isra' or '.constprop'.

    # egrep ' finish_task_switch| __netif_receive_skb_core' /proc/kallsyms
    ffffffff81135e50 t finish_task_switch.isra.0
    ffffffff81dd36d0 t __netif_receive_skb_core.constprop.0
    ffffffff8205cc0e t finish_task_switch.isra.0.cold
    ffffffff820b1aba t __netif_receive_skb_core.constprop.0.cold

To avoid this, this commit replaces the original kprobe section to
kprobe.multi in order to match symbol with wildcard characters. Here,
asterisk is used for avoiding symbol mismatch.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230818090119.477441-5-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/samples/bpf/offwaketime.bpf.c b/samples/bpf/offwaketime.bpf.c
index 8e5105811178383dfdd4ad49a02e023846a93bb6..3200a0f449690cf0f603e4788e3bc66d163d61ec 100644 (file)
--- a/samples/bpf/offwaketime.bpf.c
+++ b/samples/bpf/offwaketime.bpf.c
@@ -118,7 +118,7 @@ int oncpu(struct trace_event_raw_sched_switch *ctx)
        /* record previous thread sleep time */
        u32 pid = ctx->prev_pid;
 #else
-SEC("kprobe/finish_task_switch")
+SEC("kprobe.multi/finish_task_switch*")
 int oncpu(struct pt_regs *ctx)
 {
        struct task_struct *p = (void *) PT_REGS_PARM1(ctx);

diff --git a/samples/bpf/tracex1.bpf.c b/samples/bpf/tracex1.bpf.c
index bb78bdbffa87af4b32979ce464b6c93a6b3ee9f0..f3be14a03964da2a4274da7115ae242b41a141cb 100644 (file)
--- a/samples/bpf/tracex1.bpf.c
+++ b/samples/bpf/tracex1.bpf.c
@@ -22,11 +22,12 @@
  * Number of arguments and their positions can change, etc.
  * In such case this bpf+kprobe example will no longer be meaningful
  */
-SEC("kprobe/__netif_receive_skb_core")
+SEC("kprobe.multi/__netif_receive_skb_core*")
 int bpf_prog1(struct pt_regs *ctx)
 {
        /* attaches to kprobe __netif_receive_skb_core,
         * looks for packets on loobpack device and prints them
+        * (wildcard is used for avoiding symbol mismatch due to optimization)
         */
        char devname[IFNAMSIZ];
        struct net_device *dev;