From nobody Tue Oct 7 18:28:33 2025 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 DDF552DAFC2; Tue, 8 Jul 2025 13:25:19 +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=1751981120; cv=none; b=Xbwv50yMJ2PwZS9tgeqR/t+kKyJu84KT94mxZLVmpm0MsvkLqqai7MEk4VsP8Y2RmwOk5Yfpo33NneNvtAgiQqVhqowB+JoPBuwUdQqi2gDqeempdx+cR+3dTrZEWBqHplLpfRJl14mgySU+EErMsf1d8wIS5ELroUZmrPS/SWY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751981120; c=relaxed/simple; bh=TfiMNWvwIbj3NRpIgH9XqCJd6LNbrjlPRNb89Yx2TNE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pW7Pyy7xqmISvJaunvD/pUDpEL3kV5+7Vsekmv/L4hDwIvKaqm/+BZqrKP3zL9ymywTWEEhrK7ezNd9pVyJkirtdHqtXhemBePF/sD1cABR93fXlnW87CpH14SKdiG0u52WfhUfBK6lL0Yt+nbJ5SPRQS6CXXWGg+9QBYf+SP2w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZOz88AP9; 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="ZOz88AP9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57C52C4CEED; Tue, 8 Jul 2025 13:25:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751981119; bh=TfiMNWvwIbj3NRpIgH9XqCJd6LNbrjlPRNb89Yx2TNE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZOz88AP9DHT14DPaBFmO86ZQLaoK9ZtNo0InHnqpRT/YzbgOqkrCdI7kD7H8JSG+6 mdSH0EEJfRPOVfATLDZWw0rW5MA5QKhhe9+Y8KqUV27xFgtEudPc6CuHhvxlcBEBjQ 7wraqu7W6SCjIqD0rDcKIrVlfGWDkmXaDycbtp35ykT3KZH3CS/Kc/nY1FS0inZLLi D6RrX4xEeEHvE+GpmtnEc3IM4t6gm8Ja1mdNrswFP7f53sEfCxd3L2qcZesr1eVEYv 6ghlucxhRO4SFktiKbxnz8nw8oQGmZVSKZ/sOoiSlyS+Uonms75A+o/4hzDX/+EvJX J/w5Sne89TEZg== From: Jiri Olsa To: Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko Cc: 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 , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Ingo Molnar Subject: [PATCHv4 perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines Date: Tue, 8 Jul 2025 15:23:17 +0200 Message-ID: <20250708132333.2739553-9-jolsa@kernel.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250708132333.2739553-1-jolsa@kernel.org> References: <20250708132333.2739553-1-jolsa@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 addres= s, so while searching for available address we use is_reachable_by_call functi= on 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 --- arch/x86/kernel/uprobes.c | 169 ++++++++++++++++++++++++++++++++++++++ include/linux/uprobes.h | 6 ++ kernel/events/uprobes.c | 10 +++ kernel/fork.c | 1 + 4 files changed, 186 insertions(+) diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 77050e5a4680..6336bb961907 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -608,6 +608,175 @@ static void riprel_post_xol(struct arch_uprobe *aupro= be, struct pt_regs *regs) *sr =3D utask->autask.saved_scratch_register; } } + +static int tramp_mremap(const struct vm_special_mapping *sm, struct vm_are= a_struct *new_vma) +{ + return -EPERM; +} + +static struct page *tramp_mapping_pages[2] __ro_after_init; + +static struct vm_special_mapping tramp_mapping =3D { + .name =3D "[uprobes-trampoline]", + .mremap =3D tramp_mremap, + .pages =3D 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 =3D (long)(vaddr + 5 - vtramp); + + return delta >=3D INT_MIN && delta <=3D INT_MAX; +} + +#define __4GB (1UL << 32) +#define MASK_4GB ~(__4GB - 1) +#define PAGE_COUNT(addr) ((addr & ~MASK_4GB) >> PAGE_SHIFT) + +static unsigned long find_nearest_trampoline(unsigned long vaddr) +{ + struct vm_unmapped_area_info info =3D { + .length =3D PAGE_SIZE, + .align_mask =3D ~PAGE_MASK, + }; + unsigned long limit, low_limit =3D PAGE_SIZE, high_limit =3D TASK_SIZE; + unsigned long cross_4GB, low_4GB, high_4GB; + unsigned long low_tramp, high_tramp; + unsigned long call_end =3D vaddr + 5; + + /* + * The idea is to create a trampoline every 4GB, so we need to find free + * page closest to the 4GB alignment. We find intersecting 4GB alignment + * address and search up and down to find the closest free page. + */ + + low_4GB =3D call_end & MASK_4GB; + high_4GB =3D low_4GB + __4GB; + + /* Restrict limits to be within (PAGE_SIZE,TASK_SIZE) boundaries. */ + if (!check_add_overflow(call_end, INT_MIN, &limit)) + low_limit =3D limit; + if (low_limit =3D=3D PAGE_SIZE) + low_4GB =3D low_limit; + + high_limit =3D call_end + INT_MAX; + if (high_limit > TASK_SIZE) + high_limit =3D high_4GB =3D TASK_SIZE; + + /* Get 4GB alligned address that's within 2GB distance from call_end */ + if (low_limit <=3D low_4GB) + cross_4GB =3D low_4GB; + else + cross_4GB =3D high_4GB; + + /* Search up from intersecting 4GB alignment address. */ + info.low_limit =3D cross_4GB; + info.high_limit =3D high_limit; + high_tramp =3D vm_unmapped_area(&info); + + /* Search down from intersecting 4GB alignment address. */ + info.low_limit =3D low_limit; + info.high_limit =3D cross_4GB; + info.flags =3D VM_UNMAPPED_AREA_TOPDOWN; + low_tramp =3D 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 4GB alignment address. */ + if (cross_4GB - low_tramp < high_tramp - cross_4GB) + return low_tramp; + return high_tramp; +} + +static struct uprobe_trampoline *create_uprobe_trampoline(unsigned long va= ddr) +{ + struct pt_regs *regs =3D task_pt_regs(current); + struct mm_struct *mm =3D current->mm; + struct uprobe_trampoline *tramp; + struct vm_area_struct *vma; + + if (!user_64bit_mode(regs)) + return NULL; + + vaddr =3D find_nearest_trampoline(vaddr); + if (IS_ERR_VALUE(vaddr)) + return NULL; + + tramp =3D kzalloc(sizeof(*tramp), GFP_KERNEL); + if (unlikely(!tramp)) + return NULL; + + tramp->vaddr =3D vaddr; + vma =3D _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 =3D ¤t->mm->uprobes_state; + struct uprobe_trampoline *tramp =3D 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 =3D false; + return tramp; + } + } + + tramp =3D create_uprobe_trampoline(vaddr); + if (!tramp) + return NULL; + + *new =3D 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 =3D &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 =20 struct uprobe; struct vm_area_struct; @@ -185,6 +186,9 @@ struct xol_area; =20 struct uprobes_state { struct xol_area *xol_area; +#ifdef CONFIG_X86_64 + struct hlist_head head_tramps; +#endif }; =20 typedef int (*uprobe_write_verify_t)(struct page *page, unsigned long vadd= r, @@ -233,6 +237,8 @@ extern void uprobe_handle_trampoline(struct pt_regs *re= gs); 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; } =20 +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); =20 + arch_uprobe_clear_state(mm); + if (!area) return; =20 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 *m= m) { #ifdef CONFIG_UPROBES mm->uprobes_state.xol_area =3D NULL; + arch_uprobe_init_state(mm); #endif } =20 --=20 2.50.0