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 12FD01F5852; Sun, 20 Jul 2025 11:23:12 +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=1753010593; cv=none; b=jtlfeWemERl9uLmSAxikkxoqRtGh/2irGyXXLsAAtYfC0JgEncf24rHVwRiccvEiujT8oDQH1F9iSQK7WkL1vvBFj93a+0idIIzFf3nYJa/pxslbXZGJ5JU4AACGbXV1PYNtyoPV0tmIOqZKsTQyi+zqxJjJPTTFdyc9CzEGoQ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753010593; c=relaxed/simple; bh=8GkNnGB9PJwqATm3sX3AOk9WvCD0miwnL+LDh1/M6u0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UrnvIjPbCvMvyNU42Pu+nQZYuvgfyo5RZKWdQdHBASUxNSyWD76+OHGovfEqyyXCJilGpyKwn3VVgOS66hUlMcg2ES2HbZzPrpMAY59jGBlrNivTCTKCVmlzjF44YyZZoknZ8R/RbskQyxRc+nlOxpcq1sRU9oV+ZLjeu3YCeOg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sE/akasG; 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="sE/akasG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E3F8C4CEE7; Sun, 20 Jul 2025 11:23:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753010592; bh=8GkNnGB9PJwqATm3sX3AOk9WvCD0miwnL+LDh1/M6u0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sE/akasG850XX+dmDsddnCMSeWmAzyByllJ4irqJKpeqOmRseXzEXMjTwZw4Ghz8I kvmOdVl4nEFF69cw7DYCqGwxouXqdEd6Kkt5IyqvP4e/54XX67BSEdME9HqQIqeFdk yP/C19lNE1eNs73sqN0LW7k3Hs80xKtE6XJVy4E25E9/uNG/yjmw87J8slHi5SxbbL LWSaDS+PUziZGXcEkWywhMiF7y6u7jVHlZKHwI8EDctDYwHpGpwExYhxABE9jgKUPq dv+YiaQMwzEeO6ko4+tWHg6oV3QXjjYH5pdn20K9rMwILaGG56GYXk7vwVnJWfSOMn SC5pouoOEB8yw== From: Jiri Olsa To: Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko Cc: "Masami Hiramatsu (Google)" , 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 , Alan Maguire , David Laight , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Ingo Molnar Subject: [PATCHv6 perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines Date: Sun, 20 Jul 2025 13:21:18 +0200 Message-ID: <20250720112133.244369-9-jolsa@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250720112133.244369-1-jolsa@kernel.org> References: <20250720112133.244369-1-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Acked-by: Andrii Nakryiko Acked-by: Oleg Nesterov Acked-by: Masami Hiramatsu (Google) Signed-off-by: Jiri Olsa --- 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 1882d06b9138..78ab2009576c 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 } -- 2.50.1