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[85.193.35.130]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aab963b2611sm16857666b.174.2024.12.13.13.52.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Dec 2024 13:52:17 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 13 Dec 2024 22:52:15 +0100 To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Jiri Olsa , Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko , bpf@vger.kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Masami Hiramatsu , Alan Maguire , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 06/13] uprobes/x86: Add uprobe syscall to speed up uprobe Message-ID: References: <20241211133403.208920-1-jolsa@kernel.org> <20241211133403.208920-7-jolsa@kernel.org> <66e85401-b2ec-442d-bebe-c4ff3151e7e2@t-8ch.de> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Dec 13, 2024 at 04:12:46PM +0100, Thomas Weißschuh wrote: SNIP > > > > +static int __init arch_uprobes_init(void) > > > > +{ > > > > + unsigned long size = uprobe_trampoline_end - uprobe_trampoline_entry; > > > > + static struct page *pages[2]; > > > > + struct page *page; > > > > + > > > > + page = alloc_page(GFP_HIGHUSER); > > > > > > That page could be in static memory, removing the need for the explicit > > > allocation. It could also be __ro_after_init. > > > Then tramp_mapping itself can be const. > > > > hum, how would that look like? I think that to get proper page object > > you have to call alloc_page or some other page alloc family function.. > > what do I miss? > > static u8 trampoline_page[PAGE_SIZE] __ro_after_init __aligned(PAGE_SIZE); > static struct page *tramp_mapping_pages[2] __ro_after_init; > > static const struct vm_special_mapping tramp_mapping = { > .name = "[uprobes-trampoline]", > .pages = tramp_mapping_pages, > .mremap = tramp_mremap, > }; > > static int __init arch_uprobes_init(void) > { > ... > trampoline_pages[0] = virt_to_page(trampoline_page); > ... > } > > Untested, but it's similar to the stuff the vDSO implementations are > doing which I am working with at the moment. nice idea, better than allocating the page, will do that > > > > > > > Also this seems to waste the page on 32bit kernels. > > > > it's inside CONFIG_X86_64 ifdef > > > > > > > > > + if (!page) > > > > + return -ENOMEM; > > > > + pages[0] = page; > > > > + tramp_mapping.pages = (struct page **) &pages; > > > > > > tramp_mapping.pages = pages; ? > > > > I think the compiler will cry about *pages[2] vs **pages types mismatch, > > but I'll double check that > > It compiles for me. ok thanks, jirka