linux-kernel - [PATCH 2/3] bpf/trampoline: Allow ftrace location to differ from trampoline attach address

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Message-Id: <2a32e4723f7e56c675ffd6aa0762789e56dce2e1.1645096227.git.naveen.n.rao@linux.vnet.ibm.com>
Date:   Thu, 17 Feb 2022 17:06:24 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Nicholas Piggin <npiggin@...il.com>, <bpf@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/3] bpf/trampoline: Allow ftrace location to differ from trampoline attach address

On some architectures, ftrace location can include multiple
instructions, and does not necessarily match the function entry address
returned by kallsyms_lookup(). Drop the check in is_ftrace_location() to
accommodate the same.

Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
 kernel/bpf/trampoline.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4b6974a195c138..c47c80874bee3f 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -124,8 +124,6 @@ static int is_ftrace_location(void *ip)
 	addr = ftrace_location((long)ip);
 	if (!addr)
 		return 0;
-	if (WARN_ON_ONCE(addr != (long)ip))
-		return -EFAULT;
 	return 1;
 }
 
-- 
2.35.1