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Thu, 25 Jun 2026 06:39:08 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 25 Jun 2026 15:39:06 +0200 To: Oleg Nesterov Cc: Peter Zijlstra , Ingo Molnar , Masami Hiramatsu , Andrii Nakryiko , bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCHv4 02/13] uprobes/x86: Remove struct uprobe_trampoline object Message-ID: References: <20260526205840.173790-1-jolsa@kernel.org> <20260526205840.173790-3-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 Wed, Jun 24, 2026 at 04:36:23PM +0200, Oleg Nesterov wrote: > On 05/26, Jiri Olsa wrote: > > > > Removing struct uprobe_trampoline object and it's tracking code, > > because it's not needed. We can do same thing directly on top of > > struct vm_area_struct objects. > > > > This makes the code simpler and allows easy propagation of the > > trampoline vma object into child process in following change. > > > > Note the original code called destroy_uprobe_trampoline if the > > optimiation failed, but it only freed the struct uprobe_trampoline > > object, not the vma. The new vma leak is fixed in following change. > > > > Acked-by: Andrii Nakryiko > > Signed-off-by: Jiri Olsa > > Reviewed-by: Oleg Nesterov > > --------------------------------------------------------------------- > Although I can't convince myself I fully understand this code with or > without this patch ;) > > A couple of questions below... > > > -static struct uprobe_trampoline *create_uprobe_trampoline(unsigned long vaddr) > > +static struct vm_area_struct *get_uprobe_trampoline(struct mm_struct *mm, unsigned long vaddr) > > { > > - struct pt_regs *regs = task_pt_regs(current); > > - struct mm_struct *mm = current->mm; > > - struct uprobe_trampoline *tramp; > > + VMA_ITERATOR(vmi, mm, 0); > > struct vm_area_struct *vma; > > > > - if (!user_64bit_mode(regs)) > > - return NULL; > > + if (vaddr > TASK_SIZE || vaddr < PAGE_SIZE) > > + return ERR_PTR(-EINVAL); > > Do we really need this check? It looks a bit confusing to me... > vaddr is bp_vaddr from handle_swbp(), it should be valid? true, will remove > > > + > > + for_each_vma(vmi, vma) { > > + if (!vma_is_special_mapping(vma, &tramp_mapping)) > > + continue; > > + if (is_reachable_by_call(vma->vm_start, vaddr)) > > + return vma; > > + } > > Perhaps we can later optimize this code a bit? I mean something like > > start_reachable = ...; > end_reachable = ...; > > VMA_ITERATOR(vmi, mm, start_reachable); > > for_each_vma(vmi, vma) { > if (!vma_is_special_mapping(...)) > continue; > if (vma->vm_start > end_reachable) > break; > return vma; > } looks good, will try to use that > > > static int __arch_uprobe_optimize(struct arch_uprobe *auprobe, struct mm_struct *mm, > > unsigned long vaddr) > > { > > - struct uprobe_trampoline *tramp; > > - struct vm_area_struct *vma; > > - bool new = false; > > - int err = 0; > > + struct pt_regs *regs = task_pt_regs(current); > > + struct vm_area_struct *vma, *tramp; > > > > + if (!user_64bit_mode(regs)) > > + return -EINVAL; > > vma = find_vma(mm, vaddr); > > if (!vma) > > return -EINVAL; > > I guess find_vma() can't fail, the caller arch_uprobe_optimize() has called > copy_from_vaddr() under mmap_write_lock()... Nevermind. hum, how's that.. I'll check, but where's the magic? :) thanks, jirka