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samples/bpf: fix symbol mismatch by compiler optimization

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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>
This commit is contained in:
Daniel T. Lee 2023-08-18 18:01:14 +09:00 committed by Alexei Starovoitov
parent 4a0ee78890
commit 02dabc247a
2 changed files with 3 additions and 2 deletions
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2
samples/bpf/offwaketime.bpf.c
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@ -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);

3
samples/bpf/tracex1.bpf.c
View file

@ -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;