Re: [PATCH v2 5/5] uprobes: make uprobe_register() return struct uprobe *

From: Google
Date: Wed Jul 31 2024 - 01:40:11 EST

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In reply to: Oleg Nesterov: "[PATCH v2 5/5] uprobes: make uprobe_register() return struct uprobe *"
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On Mon, 29 Jul 2024 15:45:35 +0200
Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> This way uprobe_unregister() and uprobe_apply() can use "struct uprobe *"
> rather than inode + offset. This simplifies the code and allows to avoid
> the unnecessary find_uprobe() + put_uprobe() in these functions.
>
> TODO: uprobe_unregister() still needs get_uprobe/put_uprobe to ensure that
> this uprobe can't be freed before up_write(&uprobe->register_rwsem).

Is this TODO item, or just a note? At this moment, this is natural
to use get_uprobe() to protect uprobe itself.

Thank you,

>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> include/linux/uprobes.h | 15 +++++-----
> kernel/events/uprobes.c | 56 +++++++++++++++----------------------
> kernel/trace/bpf_trace.c | 25 ++++++++---------
> kernel/trace/trace_uprobe.c | 26 ++++++++---------
> 4 files changed, 55 insertions(+), 67 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 440316fbf3c6..137ddfc0b2f8 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -16,6 +16,7 @@
> #include <linux/types.h>
> #include <linux/wait.h>
>
> +struct uprobe;
> struct vm_area_struct;
> struct mm_struct;
> struct inode;
> @@ -110,9 +111,9 @@ extern bool is_trap_insn(uprobe_opcode_t *insn);
> extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs);
> extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs);
> extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t);
> -extern int uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
> -extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
> -extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
> +extern struct uprobe *uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
> +extern int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool);
> +extern void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc);
> extern int uprobe_mmap(struct vm_area_struct *vma);
> extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
> extern void uprobe_start_dup_mmap(void);
> @@ -150,18 +151,18 @@ static inline void uprobes_init(void)
>
> #define uprobe_get_trap_addr(regs) instruction_pointer(regs)
>
> -static inline int
> +static inline struct uprobe *
> uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc)
> {
> - return -ENOSYS;
> + return ERR_PTR(-ENOSYS);
> }
> static inline int
> -uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool add)
> +uprobe_apply(struct uprobe* uprobe, struct uprobe_consumer *uc, bool add)
> {
> return -ENOSYS;
> }
> static inline void
> -uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> +uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
> {
> }
> static inline int uprobe_mmap(struct vm_area_struct *vma)
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index b7f40bad8abc..974474680820 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1099,20 +1099,14 @@ __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
> delete_uprobe(uprobe);
> }
>
> -/*
> +/**
> * uprobe_unregister - unregister an already registered probe.
> - * @inode: the file in which the probe has to be removed.
> - * @offset: offset from the start of the file.
> + * @uprobe: uprobe to remove
> * @uc: identify which probe if multiple probes are colocated.
> */
> -void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> +void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
> {
> - struct uprobe *uprobe;
> -
> - uprobe = find_uprobe(inode, offset);
> - if (WARN_ON(!uprobe))
> - return;
> -
> + get_uprobe(uprobe);
> down_write(&uprobe->register_rwsem);
> __uprobe_unregister(uprobe, uc);
> up_write(&uprobe->register_rwsem);
> @@ -1120,7 +1114,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
> }
> EXPORT_SYMBOL_GPL(uprobe_unregister);
>
> -/*
> +/**
> * uprobe_register - register a probe
> * @inode: the file in which the probe has to be placed.
> * @offset: offset from the start of the file.
> @@ -1136,40 +1130,40 @@ EXPORT_SYMBOL_GPL(uprobe_unregister);
> * unregisters. Caller of uprobe_register() is required to keep @inode
> * (and the containing mount) referenced.
> *
> - * Return errno if it cannot successully install probes
> - * else return 0 (success)
> + * Return: pointer to the new uprobe on success or an ERR_PTR on failure.
> */
> -int uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset,
> - struct uprobe_consumer *uc)
> +struct uprobe *uprobe_register(struct inode *inode,
> + loff_t offset, loff_t ref_ctr_offset,
> + struct uprobe_consumer *uc)
> {
> struct uprobe *uprobe;
> int ret;
>
> /* Uprobe must have at least one set consumer */
> if (!uc->handler && !uc->ret_handler)
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
>
> /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
> if (!inode->i_mapping->a_ops->read_folio &&
> !shmem_mapping(inode->i_mapping))
> - return -EIO;
> + return ERR_PTR(-EIO);
> /* Racy, just to catch the obvious mistakes */
> if (offset > i_size_read(inode))
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
>
> /*
> * This ensures that copy_from_page(), copy_to_page() and
> * __update_ref_ctr() can't cross page boundary.
> */
> if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE))
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
> if (!IS_ALIGNED(ref_ctr_offset, sizeof(short)))
> - return -EINVAL;
> + return ERR_PTR(-EINVAL);
>
> retry:
> uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
> if (IS_ERR(uprobe))
> - return PTR_ERR(uprobe);
> + return uprobe;
>
> /*
> * We can race with uprobe_unregister()->delete_uprobe().
> @@ -1188,35 +1182,29 @@ int uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset,
>
> if (unlikely(ret == -EAGAIN))
> goto retry;
> - return ret;
> +
> + return ret ? ERR_PTR(ret) : uprobe;
> }
> EXPORT_SYMBOL_GPL(uprobe_register);
>
> -/*
> - * uprobe_apply - unregister an already registered probe.
> - * @inode: the file in which the probe has to be removed.
> - * @offset: offset from the start of the file.
> +/**
> + * uprobe_apply - add or remove the breakpoints according to @uc->filter
> + * @uprobe: uprobe which "owns" the breakpoint
> * @uc: consumer which wants to add more or remove some breakpoints
> * @add: add or remove the breakpoints
> + * Return: 0 on success or negative error code.
> */
> -int uprobe_apply(struct inode *inode, loff_t offset,
> - struct uprobe_consumer *uc, bool add)
> +int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool add)
> {
> - struct uprobe *uprobe;
> struct uprobe_consumer *con;
> int ret = -ENOENT;
>
> - uprobe = find_uprobe(inode, offset);
> - if (WARN_ON(!uprobe))
> - return ret;
> -
> down_write(&uprobe->register_rwsem);
> for (con = uprobe->consumers; con && con != uc ; con = con->next)
> ;
> if (con)
> ret = register_for_each_vma(uprobe, add ? uc : NULL);
> up_write(&uprobe->register_rwsem);
> - put_uprobe(uprobe);
>
> return ret;
> }
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index afa909e17824..4e391daafa64 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3160,6 +3160,7 @@ struct bpf_uprobe {
> loff_t offset;
> unsigned long ref_ctr_offset;
> u64 cookie;
> + struct uprobe *uprobe;
> struct uprobe_consumer consumer;
> };
>
> @@ -3178,15 +3179,12 @@ struct bpf_uprobe_multi_run_ctx {
> struct bpf_uprobe *uprobe;
> };
>
> -static void bpf_uprobe_unregister(struct path *path, struct bpf_uprobe *uprobes,
> - u32 cnt)
> +static void bpf_uprobe_unregister(struct bpf_uprobe *uprobes, u32 cnt)
> {
> u32 i;
>
> - for (i = 0; i < cnt; i++) {
> - uprobe_unregister(d_real_inode(path->dentry), uprobes[i].offset,
> - &uprobes[i].consumer);
> - }
> + for (i = 0; i < cnt; i++)
> + uprobe_unregister(uprobes[i].uprobe, &uprobes[i].consumer);
> }
>
> static void bpf_uprobe_multi_link_release(struct bpf_link *link)
> @@ -3194,7 +3192,7 @@ static void bpf_uprobe_multi_link_release(struct bpf_link *link)
> struct bpf_uprobe_multi_link *umulti_link;
>
> umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
> - bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
> + bpf_uprobe_unregister(umulti_link->uprobes, umulti_link->cnt);
> if (umulti_link->task)
> put_task_struct(umulti_link->task);
> path_put(&umulti_link->path);
> @@ -3480,12 +3478,13 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
> &bpf_uprobe_multi_link_lops, prog);
>
> for (i = 0; i < cnt; i++) {
> - err = uprobe_register(d_real_inode(link->path.dentry),
> - uprobes[i].offset,
> - uprobes[i].ref_ctr_offset,
> - &uprobes[i].consumer);
> - if (err) {
> - bpf_uprobe_unregister(&path, uprobes, i);
> + uprobes[i].uprobe = uprobe_register(d_real_inode(link->path.dentry),
> + uprobes[i].offset,
> + uprobes[i].ref_ctr_offset,
> + &uprobes[i].consumer);
> + if (IS_ERR(uprobes[i].uprobe)) {
> + err = PTR_ERR(uprobes[i].uprobe);
> + bpf_uprobe_unregister(uprobes, i);
> goto error_free;
> }
> }
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 1f590f989c1e..52e76a73fa7c 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -58,8 +58,8 @@ struct trace_uprobe {
> struct dyn_event devent;
> struct uprobe_consumer consumer;
> struct path path;
> - struct inode *inode;
> char *filename;
> + struct uprobe *uprobe;
> unsigned long offset;
> unsigned long ref_ctr_offset;
> unsigned long nhit;
> @@ -1084,16 +1084,16 @@ typedef bool (*filter_func_t)(struct uprobe_consumer *self,
>
> static int trace_uprobe_enable(struct trace_uprobe *tu, filter_func_t filter)
> {
> - int ret;
> + struct inode *inode = d_real_inode(tu->path.dentry);
> + struct uprobe *uprobe;
>
> tu->consumer.filter = filter;
> - tu->inode = d_real_inode(tu->path.dentry);
> -
> - ret = uprobe_register(tu->inode, tu->offset, tu->ref_ctr_offset, &tu->consumer);
> - if (ret)
> - tu->inode = NULL;
> + uprobe = uprobe_register(inode, tu->offset, tu->ref_ctr_offset, &tu->consumer);
> + if (IS_ERR(uprobe))
> + return PTR_ERR(uprobe);
>
> - return ret;
> + tu->uprobe = uprobe;
> + return 0;
> }
>
> static void __probe_event_disable(struct trace_probe *tp)
> @@ -1104,11 +1104,11 @@ static void __probe_event_disable(struct trace_probe *tp)
> WARN_ON(!uprobe_filter_is_empty(tu->tp.event->filter));
>
> list_for_each_entry(tu, trace_probe_probe_list(tp), tp.list) {
> - if (!tu->inode)
> + if (!tu->uprobe)
> continue;
>
> - uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
> - tu->inode = NULL;
> + uprobe_unregister(tu->uprobe, &tu->consumer);
> + tu->uprobe = NULL;
> }
> }
>
> @@ -1305,7 +1305,7 @@ static int uprobe_perf_close(struct trace_event_call *call,
> return 0;
>
> list_for_each_entry(tu, trace_probe_probe_list(tp), tp.list) {
> - ret = uprobe_apply(tu->inode, tu->offset, &tu->consumer, false);
> + ret = uprobe_apply(tu->uprobe, &tu->consumer, false);
> if (ret)
> break;
> }
> @@ -1329,7 +1329,7 @@ static int uprobe_perf_open(struct trace_event_call *call,
> return 0;
>
> list_for_each_entry(tu, trace_probe_probe_list(tp), tp.list) {
> - err = uprobe_apply(tu->inode, tu->offset, &tu->consumer, true);
> + err = uprobe_apply(tu->uprobe, &tu->consumer, true);
> if (err) {
> uprobe_perf_close(call, event);
> break;
> --
> 2.25.1.362.g51ebf55
>
>

--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

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