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[RFC,bpf-next,1/4] bpf: Rollback to text_poke when arch not supported ftrace direct call

Message ID 20221219133736.1387008-2-pulehui@huaweicloud.com (mailing list archive)
State Superseded
Headers show
Series Support bpf trampoline for RV64 | expand

Checks

Context Check Description
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Commit Message

Pu Lehui Dec. 19, 2022, 1:37 p.m. UTC 
From: Pu Lehui <pulehui@huawei.com>

The current bpf trampoline attach to kernel functions via ftrace direct
call API, while text_poke is applied for bpf2bpf attach and tail call
optimization. For architectures that do not support ftrace direct call,
text_poke is still able to attach bpf trampoline to kernel functions.
Let's relax it by rollback to text_poke when architecture not supported.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
---
 kernel/bpf/trampoline.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)
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Patch

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index d6395215b849..386197a7952c 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -228,15 +228,11 @@  static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
 static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 {
 	void *ip = tr->func.addr;
-	unsigned long faddr;
 	int ret;
 
-	faddr = ftrace_location((unsigned long)ip);
-	if (faddr) {
-		if (!tr->fops)
-			return -ENOTSUPP;
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS) &&
+	    !!ftrace_location((unsigned long)ip))
 		tr->func.ftrace_managed = true;
-	}
 
 	if (bpf_trampoline_module_get(tr))
 		return -ENOENT;