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[37.188.177.177]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493be4dd77bsm188855e9.10.2026.06.30.07.48.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2026 07:48:34 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 30 Jun 2026 16:48:30 +0200 To: Oleg Nesterov Cc: Jiri Olsa , Peter Zijlstra , Ingo Molnar , Masami Hiramatsu , Andrii Nakryiko , bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCHv4 05/13] uprobes/x86: Move optimized uprobe from nop5 to nop10 Message-ID: References: <20260526205840.173790-1-jolsa@kernel.org> <20260526205840.173790-6-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Jun 29, 2026 at 06:40:07PM +0200, Oleg Nesterov wrote: > On 06/29, Jiri Olsa wrote: > > > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -265,6 +265,10 @@ static bool is_prefix_bad(struct insn *insn) > > > > attr = inat_get_opcode_attribute(p); > > switch (attr) { > > + case INAT_MAKE_PREFIX(INAT_PFX_CS): > > + if (insn->x86_64) > > + break; > > + fallthrough; > > case INAT_MAKE_PREFIX(INAT_PFX_ES): > > case INAT_MAKE_PREFIX(INAT_PFX_DS): > > case INAT_MAKE_PREFIX(INAT_PFX_SS): > > > > or we could just skip it for nop10.. maybe that's better > > Well, if you ask me I'd agree with the "maybe that's better" plan ;) > I mean... I don't think that INAT_PFX_CS should be "special" in is_prefix_bad. > > But, whatever you do - I agree, feel free to keep my r-b. I ended up with the bigger change below, wdyt? jirka --- diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 92626fce06a9..521a120a0c78 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -266,6 +266,7 @@ static bool is_prefix_bad(struct insn *insn) attr = inat_get_opcode_attribute(p); switch (attr) { case INAT_MAKE_PREFIX(INAT_PFX_ES): + case INAT_MAKE_PREFIX(INAT_PFX_CS): case INAT_MAKE_PREFIX(INAT_PFX_DS): case INAT_MAKE_PREFIX(INAT_PFX_SS): case INAT_MAKE_PREFIX(INAT_PFX_LOCK): @@ -275,15 +276,9 @@ static bool is_prefix_bad(struct insn *insn) return false; } -static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool x86_64) +static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn) { - enum insn_mode m = x86_64 ? INSN_MODE_64 : INSN_MODE_32; u32 volatile *good_insns; - int ret; - - ret = insn_decode(insn, auprobe->insn, sizeof(auprobe->insn), m); - if (ret < 0) - return -ENOEXEC; if (is_prefix_bad(insn)) return -ENOTSUPP; @@ -292,7 +287,7 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool if (insn_masking_exception(insn)) return -ENOTSUPP; - if (x86_64) + if (insn->x86_64) good_insns = good_insns_64; else good_insns = good_insns_32; @@ -1620,16 +1615,26 @@ static int push_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) */ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr) { + enum insn_mode m = is_64bit_mm(mm) ? INSN_MODE_64 : INSN_MODE_32; u8 fix_ip_or_call = UPROBE_FIX_IP; struct insn insn; int ret; - ret = uprobe_init_insn(auprobe, &insn, is_64bit_mm(mm)); - if (ret) - return ret; + ret = insn_decode(&insn, auprobe->insn, sizeof(auprobe->insn), m); + if (ret < 0) + return -ENOEXEC; - if (can_optimize(&insn, addr)) + /* + * No need to check instruction in uprobe_init_insn in case we + * are on top of optimizable nop10. + */ + if (can_optimize(&insn, addr)) { set_bit(ARCH_UPROBE_FLAG_CAN_OPTIMIZE, &auprobe->flags); + } else { + ret = uprobe_init_insn(auprobe, &insn); + if (ret) + return ret; + } ret = branch_setup_xol_ops(auprobe, &insn); if (ret != -ENOSYS)