linux-kernel - Re: [PATCH bpf-next 2/2] rethook: kprobes: x86: Replace kretprobe with rethook on x86

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Message-ID: <20220325100940.GM8939@worktop.programming.kicks-ass.net>
Date:   Fri, 25 Mar 2022 11:09:40 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        kernel-janitors@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH bpf-next 2/2] rethook: kprobes: x86: Replace kretprobe
 with rethook on x86

On Fri, Mar 25, 2022 at 01:29:01PM +0900, Masami Hiramatsu wrote:
> Replaces the kretprobe code with rethook on x86. With this patch,
> kretprobe on x86 uses the rethook instead of kretprobe specific
> trampoline code.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  arch/x86/Kconfig                 |    1 
>  arch/x86/include/asm/unwind.h    |   23 +++----
>  arch/x86/kernel/Makefile         |    1 
>  arch/x86/kernel/kprobes/common.h |    1 
>  arch/x86/kernel/kprobes/core.c   |  107 ----------------------------------
>  arch/x86/kernel/rethook.c        |  121 ++++++++++++++++++++++++++++++++++++++
>  6 files changed, 135 insertions(+), 119 deletions(-)
>  create mode 100644 arch/x86/kernel/rethook.c

I'm thinking you'll find it builds much better with this on...

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 2de3c8c5eba9..794fdef2501a 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -550,15 +550,15 @@ bool unwind_next_frame(struct unwind_state *state)
 		}
 		/*
 		 * There is a small chance to interrupt at the entry of
-		 * __kretprobe_trampoline() where the ORC info doesn't exist.
-		 * That point is right after the RET to __kretprobe_trampoline()
+		 * arch_rethook_trampoline() where the ORC info doesn't exist.
+		 * That point is right after the RET to arch_rethook_trampoline()
 		 * which was modified return address.
-		 * At that point, the @addr_p of the unwind_recover_kretprobe()
+		 * At that point, the @addr_p of the unwind_recover_rethook()
 		 * (this has to point the address of the stack entry storing
 		 * the modified return address) must be "SP - (a stack entry)"
 		 * because SP is incremented by the RET.
 		 */
-		state->ip = unwind_recover_kretprobe(state, state->ip,
+		state->ip = unwind_recover_rethook(state, state->ip,
 				(unsigned long *)(state->sp - sizeof(long)));
 		state->regs = (struct pt_regs *)sp;
 		state->prev_regs = NULL;
@@ -573,7 +573,7 @@ bool unwind_next_frame(struct unwind_state *state)
 			goto err;
 		}
 		/* See UNWIND_HINT_TYPE_REGS case comment. */
-		state->ip = unwind_recover_kretprobe(state, state->ip,
+		state->ip = unwind_recover_rethook(state, state->ip,
 				(unsigned long *)(state->sp - sizeof(long)));
 
 		if (state->full_regs)