From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2678D22F767; Mon, 14 Jul 2025 07:23:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752477824; cv=none; b=QQAj/lSbO77qBb85an2lQLeqflM3CZGwokQWTkIyrUj07WR33iP77eCGETgoS9nOsIFbV2Z33+bApR27JoIqQu/IJK1BOrvYxv/uk26NbP8UvXJn5wD+3RH6sWezYi0yIK6GQnt8TYOdS0FfDccX1/gPA/yzQDHLFfc9p2YOiAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752477824; c=relaxed/simple; bh=IYR1PWD+TFjz+HdMhUoBPAdd7rh92NNnRH3cV7LbYSM=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=GmVxjidfXM32f/YduR9dAdS7Ccao2nD8WZ0xSBim9p2Sg6RUpKTTwCxmI+O8a7Dg2vZdsLls5KCqA9ozYDp8J7RHmPGdkSy2/pl2gtet9uPnDpWBc0BT2837ft6QwWyBppEobqUGjzg0MsJ2LKNPYCOyT56o6XJw9IKGsqBIWHE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ibCNhVJE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ibCNhVJE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89F9AC4CEED; Mon, 14 Jul 2025 07:23:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752477822; bh=IYR1PWD+TFjz+HdMhUoBPAdd7rh92NNnRH3cV7LbYSM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ibCNhVJEzhMI0W7M9WIBfCK4fCRK4YjqB0JwcbDjDwKLBpZ7KWOvWHY0ybyYGn8Yy fk6S3o2I5o3t5DZ7cw8F8PLFIz1xLi9rYMhHclQs/RNWVQZV1l+b3WuTuf5m4c9T4s xenT7ltaDDJ5lgNPZoMsjr9Sjt8/9pM1M080iRYl16V4/JOyQJ2e9V+vHz0l6IRHfh UTo7yZkMQnJsq8gYRSFzjIHMEBuubOkhLz4pUwxgRMZkGtM+PjaN3zqI3RvfdsI/5r D9tzfYMdY8agkdRRUNRdck3DFq/06fH6zsAqiZzLehA0xJmvro5l1egGvYCGWHUbnR 2esd0UNwXzrfw== Date: Mon, 14 Jul 2025 16:23:38 +0900 From: Masami Hiramatsu (Google) To: Jiri Olsa Cc: Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Masami Hiramatsu , Alan Maguire , David Laight , Thomas =?UTF-8?B?V2Vpw59zY2h1aA==?= , Ingo Molnar Subject: Re: [PATCHv5 perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines Message-Id: <20250714162338.0c9e13b530c835f3010b3ff0@kernel.org> In-Reply-To: <20250711082931.3398027-9-jolsa@kernel.org> References: <20250711082931.3398027-1-jolsa@kernel.org> <20250711082931.3398027-9-jolsa@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 11 Jul 2025 10:29:16 +0200 Jiri Olsa wrote: > Adding support to add special mapping for user space trampoline with > following functions: > > uprobe_trampoline_get - find or add uprobe_trampoline > uprobe_trampoline_put - remove or destroy uprobe_trampoline > > The user space trampoline is exported as arch specific user space special > mapping through tramp_mapping, which is initialized in following changes > with new uprobe syscall. > > The uprobe trampoline needs to be callable/reachable from the probed address, > so while searching for available address we use is_reachable_by_call function > to decide if the uprobe trampoline is callable from the probe address. > > All uprobe_trampoline objects are stored in uprobes_state object and are > cleaned up when the process mm_struct goes down. Adding new arch hooks > for that, because this change is x86_64 specific. > > Locking is provided by callers in following changes. > > Signed-off-by: Jiri Olsa Looks good to me. Acked-by: Masami Hiramatsu (Google) Thank you! > --- > arch/x86/kernel/uprobes.c | 144 ++++++++++++++++++++++++++++++++++++++ > include/linux/uprobes.h | 6 ++ > kernel/events/uprobes.c | 10 +++ > kernel/fork.c | 1 + > 4 files changed, 161 insertions(+) > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > index 77050e5a4680..6c4dcbdd0c3c 100644 > --- a/arch/x86/kernel/uprobes.c > +++ b/arch/x86/kernel/uprobes.c > @@ -608,6 +608,150 @@ static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) > *sr = utask->autask.saved_scratch_register; > } > } > + > +static int tramp_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma) > +{ > + return -EPERM; > +} > + > +static struct page *tramp_mapping_pages[2] __ro_after_init; > + > +static struct vm_special_mapping tramp_mapping = { > + .name = "[uprobes-trampoline]", > + .mremap = tramp_mremap, > + .pages = tramp_mapping_pages, > +}; > + > +struct uprobe_trampoline { > + struct hlist_node node; > + unsigned long vaddr; > +}; > + > +static bool is_reachable_by_call(unsigned long vtramp, unsigned long vaddr) > +{ > + long delta = (long)(vaddr + 5 - vtramp); > + > + return delta >= INT_MIN && delta <= INT_MAX; > +} > + > +static unsigned long find_nearest_trampoline(unsigned long vaddr) > +{ > + struct vm_unmapped_area_info info = { > + .length = PAGE_SIZE, > + .align_mask = ~PAGE_MASK, > + }; > + unsigned long low_limit, high_limit; > + unsigned long low_tramp, high_tramp; > + unsigned long call_end = vaddr + 5; > + > + if (check_add_overflow(call_end, INT_MIN, &low_limit)) > + low_limit = PAGE_SIZE; > + > + high_limit = call_end + INT_MAX; > + > + /* Search up from the caller address. */ > + info.low_limit = call_end; > + info.high_limit = min(high_limit, TASK_SIZE); > + high_tramp = vm_unmapped_area(&info); > + > + /* Search down from the caller address. */ > + info.low_limit = max(low_limit, PAGE_SIZE); > + info.high_limit = call_end; > + info.flags = VM_UNMAPPED_AREA_TOPDOWN; > + low_tramp = vm_unmapped_area(&info); > + > + if (IS_ERR_VALUE(high_tramp) && IS_ERR_VALUE(low_tramp)) > + return -ENOMEM; > + if (IS_ERR_VALUE(high_tramp)) > + return low_tramp; > + if (IS_ERR_VALUE(low_tramp)) > + return high_tramp; > + > + /* Return address that's closest to the caller address. */ > + if (call_end - low_tramp < high_tramp - call_end) > + return low_tramp; > + return high_tramp; > +} > + > +static struct uprobe_trampoline *create_uprobe_trampoline(unsigned long vaddr) > +{ > + struct pt_regs *regs = task_pt_regs(current); > + struct mm_struct *mm = current->mm; > + struct uprobe_trampoline *tramp; > + struct vm_area_struct *vma; > + > + if (!user_64bit_mode(regs)) > + return NULL; > + > + vaddr = find_nearest_trampoline(vaddr); > + if (IS_ERR_VALUE(vaddr)) > + return NULL; > + > + tramp = kzalloc(sizeof(*tramp), GFP_KERNEL); > + if (unlikely(!tramp)) > + return NULL; > + > + tramp->vaddr = vaddr; > + vma = _install_special_mapping(mm, tramp->vaddr, PAGE_SIZE, > + VM_READ|VM_EXEC|VM_MAYEXEC|VM_MAYREAD|VM_DONTCOPY|VM_IO, > + &tramp_mapping); > + if (IS_ERR(vma)) { > + kfree(tramp); > + return NULL; > + } > + return tramp; > +} > + > +__maybe_unused > +static struct uprobe_trampoline *get_uprobe_trampoline(unsigned long vaddr, bool *new) > +{ > + struct uprobes_state *state = ¤t->mm->uprobes_state; > + struct uprobe_trampoline *tramp = NULL; > + > + if (vaddr > TASK_SIZE || vaddr < PAGE_SIZE) > + return NULL; > + > + hlist_for_each_entry(tramp, &state->head_tramps, node) { > + if (is_reachable_by_call(tramp->vaddr, vaddr)) { > + *new = false; > + return tramp; > + } > + } > + > + tramp = create_uprobe_trampoline(vaddr); > + if (!tramp) > + return NULL; > + > + *new = true; > + hlist_add_head(&tramp->node, &state->head_tramps); > + return tramp; > +} > + > +static void destroy_uprobe_trampoline(struct uprobe_trampoline *tramp) > +{ > + /* > + * We do not unmap and release uprobe trampoline page itself, > + * because there's no easy way to make sure none of the threads > + * is still inside the trampoline. > + */ > + hlist_del(&tramp->node); > + kfree(tramp); > +} > + > +void arch_uprobe_init_state(struct mm_struct *mm) > +{ > + INIT_HLIST_HEAD(&mm->uprobes_state.head_tramps); > +} > + > +void arch_uprobe_clear_state(struct mm_struct *mm) > +{ > + struct uprobes_state *state = &mm->uprobes_state; > + struct uprobe_trampoline *tramp; > + struct hlist_node *n; > + > + hlist_for_each_entry_safe(tramp, n, &state->head_tramps, node) > + destroy_uprobe_trampoline(tramp); > +} > #else /* 32-bit: */ > /* > * No RIP-relative addressing on 32-bit > diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h > index 5080619560d4..b40d33aae016 100644 > --- a/include/linux/uprobes.h > +++ b/include/linux/uprobes.h > @@ -17,6 +17,7 @@ > #include > #include > #include > +#include > > struct uprobe; > struct vm_area_struct; > @@ -185,6 +186,9 @@ struct xol_area; > > struct uprobes_state { > struct xol_area *xol_area; > +#ifdef CONFIG_X86_64 > + struct hlist_head head_tramps; > +#endif > }; > > typedef int (*uprobe_write_verify_t)(struct page *page, unsigned long vaddr, > @@ -233,6 +237,8 @@ extern void uprobe_handle_trampoline(struct pt_regs *regs); > extern void *arch_uretprobe_trampoline(unsigned long *psize); > extern unsigned long uprobe_get_trampoline_vaddr(void); > extern void uprobe_copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len); > +extern void arch_uprobe_clear_state(struct mm_struct *mm); > +extern void arch_uprobe_init_state(struct mm_struct *mm); > #else /* !CONFIG_UPROBES */ > struct uprobes_state { > }; > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 6795b8d82b9c..acec91a676b7 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1802,6 +1802,14 @@ static struct xol_area *get_xol_area(void) > return area; > } > > +void __weak arch_uprobe_clear_state(struct mm_struct *mm) > +{ > +} > + > +void __weak arch_uprobe_init_state(struct mm_struct *mm) > +{ > +} > + > /* > * uprobe_clear_state - Free the area allocated for slots. > */ > @@ -1813,6 +1821,8 @@ void uprobe_clear_state(struct mm_struct *mm) > delayed_uprobe_remove(NULL, mm); > mutex_unlock(&delayed_uprobe_lock); > > + arch_uprobe_clear_state(mm); > + > if (!area) > return; > > diff --git a/kernel/fork.c b/kernel/fork.c > index bd8c21d64746..70f2d4e2e8fe 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1009,6 +1009,7 @@ static void mm_init_uprobes_state(struct mm_struct *mm) > { > #ifdef CONFIG_UPROBES > mm->uprobes_state.xol_area = NULL; > + arch_uprobe_init_state(mm); > #endif > } > > -- > 2.50.0 > -- Masami Hiramatsu (Google)