linux-kernel - Re: [PATCHv6 perf/core 10/22] uprobes/x86: Add support to optimize uprobes

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Message-ID: <aLfkzE_eMYE40QjD@krava>
Date: Wed, 3 Sep 2025 08:48:44 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Andrii Nakryiko <andrii@...nel.org>,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, x86@...nel.org,
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...lab.com>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv6 perf/core 10/22] uprobes/x86: Add support to optimize
 uprobes

On Tue, Aug 19, 2025 at 09:15:15PM +0200, Peter Zijlstra wrote:
> On Sun, Jul 20, 2025 at 01:21:20PM +0200, Jiri Olsa wrote:
> 
> > +static bool __is_optimized(uprobe_opcode_t *insn, unsigned long vaddr)
> > +{
> > +	struct __packed __arch_relative_insn {
> > +		u8 op;
> > +		s32 raddr;
> > +	} *call = (struct __arch_relative_insn *) insn;
> 
> Not something you need to clean up now I suppose, but we could do with
> unifying this thing. we have a bunch of instances around.

found two below, maybe we could use 'union text_poke_insn' instead like below?

jirka


---
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 6079d15dab8c..7fd03897d776 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -109,14 +109,10 @@ const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
 static nokprobe_inline void
 __synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
 {
-	struct __arch_relative_insn {
-		u8 op;
-		s32 raddr;
-	} __packed *insn;
-
-	insn = (struct __arch_relative_insn *)dest;
-	insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
-	insn->op = op;
+	union text_poke_insn *insn = dest;
+
+	insn->disp = (s32)((long)(to) - ((long)(from) + 5));
+	insn->opcode = op;
 }
 
 /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 0a8c0a4a5423..bac14f3165c3 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -1046,14 +1046,11 @@ static int copy_from_vaddr(struct mm_struct *mm, unsigned long vaddr, void *dst,
 
 static bool __is_optimized(uprobe_opcode_t *insn, unsigned long vaddr)
 {
-	struct __packed __arch_relative_insn {
-		u8 op;
-		s32 raddr;
-	} *call = (struct __arch_relative_insn *) insn;
+	union text_poke_insn *call = (union text_poke_insn *) insn;
 
 	if (!is_call_insn(insn))
 		return false;
-	return __in_uprobe_trampoline(vaddr + 5 + call->raddr);
+	return __in_uprobe_trampoline(vaddr + 5 + call->disp);
 }
 
 static int is_optimized(struct mm_struct *mm, unsigned long vaddr)