From 02dabc247ad68b41758bf39f11e2d682b8b32dd7 Mon Sep 17 00:00:00 2001
From: "Daniel T. Lee" <danieltimlee@gmail.com>
Date: Fri, 18 Aug 2023 18:01:14 +0900
Subject: [PATCH] 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>
---
samples/bpf/offwaketime.bpf.c | 2 +-
samples/bpf/tracex1.bpf.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/samples/bpf/offwaketime.bpf.c b/samples/bpf/offwaketime.bpf.c
index 8e51058111783..3200a0f449690 100644
--- 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 bb78bdbffa87a..f3be14a03964d 100644
--- 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;
--
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