From: Song Shuai <suagrfillet@gmail.com>
To: guoren@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org,
mark.rutland@arm.com, paul.walmsley@sifive.com,
palmer@dabbelt.com, aou@eecs.berkeley.edu
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
Song Shuai <suagrfillet@gmail.com>
Subject: [PATCH] riscv/ftrace: fix ftrace_modify_call bug
Date: Tue, 22 Nov 2022 15:54:40 +0800 [thread overview]
Message-ID: <20221122075440.1165172-1-suagrfillet@gmail.com> (raw)
With this commit (riscv: ftrace: Reduce the detour code size to half)
patched, ftrace bug occurred When hosting kprobe and function tracer
at the same function.
Obviously, the variable caller in ftrace_modify_call was assigned by
rec->ip with 4 offset failing the code replacing at function entry.
And the caller should be assigned by rec->ip directly to indicate
the function entry.
The following is the ftrace bug log.
```
[ 419.632855] 00000000f8776803: expected (ffe00297 1a4282e7) but got (1a8282e7 f0227179)
[ 419.633390] ------------[ ftrace bug ]------------
[ 419.633553] ftrace failed to modify
[ 419.633569] [<ffffffff802091cc>] kernel_read+0x0/0x52
[ 419.633863] actual: 97:02:e0:ff:e7:82:82:1a
[ 419.634087] Updating ftrace call site to call a different ftrace function
[ 419.634279] ftrace record flags: e0000002
[ 419.634487] (2) R
[ 419.634487] expected tramp: ffffffff800093cc
[ 419.634935] ------------[ cut here ]------------
```
Signed-off-by: Song Shuai <suagrfillet@gmail.com>
---
arch/riscv/kernel/ftrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 8c77f236fc71..61b24d767e2e 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -132,7 +132,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned int call[2];
- unsigned long caller = rec->ip + 4;
+ unsigned long caller = rec->ip;
int ret;
make_call_t0(caller, old_addr, call);
--
2.20.1
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next reply other threads:[~2022-11-22 7:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-22 7:54 Song Shuai [this message]
2022-11-22 8:57 ` [PATCH] riscv/ftrace: fix ftrace_modify_call bug Guo Ren
2022-11-22 9:11 ` Song Shuai
[not found] ` <CAJF2gTT=r4VeWqpe+Tw2JDdTDU+r2mJiPmHq_i8eV5YRmrrLRA@mail.gmail.com>
2022-11-22 9:51 ` Song Shuai
2022-11-22 8:57 ` Conor Dooley
2022-11-22 9:46 ` Song Shuai
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