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Message-ID: <CAP-5=fXtWMo2fqZe9sTr_3eanWsyoBLEpo-SFM+RE+V1jKYTjw@mail.gmail.com>
Date: Wed, 11 Jan 2023 13:35:05 -0800
From: Ian Rogers <irogers@...gle.com>
To: luolongjun@...wei.com
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
mark.rutland@....com, alexander.shishkin@...ux.intel.com,
jolsa@...nel.org, namhyung@...nel.org,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
sangyan@...wei.com, luanjianhai@...wei.com, zhuling8@...wei.com,
lizongwu@...wei.com, luolongjuna@...il.com
Subject: Re: [PATCH] uprobes: list all active uprobes in the system
On Wed, Jan 11, 2023 at 2:49 AM <luolongjun@...wei.com> wrote:
>
> From: Longjun Luo <luolongjun@...wei.com>
>
> Since uprobes will replace instructions in the process
> memory, it is necessary to provide one way to list
> all active uprobes. One can access this file through
> /sys/kernel/debug/uprobes/list.
>
> Output looks like this
> =====================
> inode+offset/ref_ctr_offset 4160760670+0x30a10/0x0
> ref 1
> register_rwsem (unlocked)
> consumer_rwsem (unlocked)
> consumers-1
> handler 0xffffffffc03ee02e(handler) uprobe
> ret_handler 0x0000000000000000( )
> filter 0xffffffffc03ee010(filter) uprobe
> consumers-2
> handler 0xffffffffc03e902e(handler_1) uprobe_1
> ret_handler 0x0000000000000000( )
> filter 0xffffffffc03e9010(filter_1) uprobe_1
>
> Signed-off-by: Longjun Luo <luolongjun@...wei.com>
> ---
> kernel/events/uprobes.c | 120 ++++++++++++++++++++++++++++++++++++----
> 1 file changed, 109 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index d9e357b7e17c..2fa9b910abc7 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -27,6 +27,9 @@
> #include <linux/task_work.h>
> #include <linux/shmem_fs.h>
> #include <linux/khugepaged.h>
> +#include <linux/rbtree.h>
> +#include <linux/debugfs.h>
> +#include <linux/kallsyms.h>
>
> #include <linux/uprobes.h>
>
> @@ -40,7 +43,7 @@ static struct rb_root uprobes_tree = RB_ROOT;
> */
> #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
>
> -static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
> +static DECLARE_RWSEM(uprobes_treelock); /* serialize rbtree access */
>
> #define UPROBES_HASH_SZ 13
> /* serialize uprobe->pending_list */
> @@ -672,9 +675,9 @@ static struct uprobe *find_uprobe(struct inode *inode, loff_t offset)
> {
> struct uprobe *uprobe;
>
> - spin_lock(&uprobes_treelock);
> + down_read(&uprobes_treelock);
> uprobe = __find_uprobe(inode, offset);
> - spin_unlock(&uprobes_treelock);
> + up_read(&uprobes_treelock);
>
> return uprobe;
> }
> @@ -704,9 +707,9 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
> {
> struct uprobe *u;
>
> - spin_lock(&uprobes_treelock);
> + down_write(&uprobes_treelock);
> u = __insert_uprobe(uprobe);
> - spin_unlock(&uprobes_treelock);
> + up_write(&uprobes_treelock);
>
> return u;
> }
> @@ -938,9 +941,9 @@ static void delete_uprobe(struct uprobe *uprobe)
> if (WARN_ON(!uprobe_is_active(uprobe)))
> return;
>
> - spin_lock(&uprobes_treelock);
> + down_write(&uprobes_treelock);
> rb_erase(&uprobe->rb_node, &uprobes_tree);
> - spin_unlock(&uprobes_treelock);
> + up_write(&uprobes_treelock);
> RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
> put_uprobe(uprobe);
> }
> @@ -1301,7 +1304,7 @@ static void build_probe_list(struct inode *inode,
> min = vaddr_to_offset(vma, start);
> max = min + (end - start) - 1;
>
> - spin_lock(&uprobes_treelock);
> + down_read(&uprobes_treelock);
> n = find_node_in_range(inode, min, max);
> if (n) {
> for (t = n; t; t = rb_prev(t)) {
> @@ -1319,7 +1322,7 @@ static void build_probe_list(struct inode *inode,
> get_uprobe(u);
> }
> }
> - spin_unlock(&uprobes_treelock);
> + up_read(&uprobes_treelock);
> }
>
> /* @vma contains reference counter, not the probed instruction. */
> @@ -1410,9 +1413,9 @@ vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long e
> min = vaddr_to_offset(vma, start);
> max = min + (end - start) - 1;
>
> - spin_lock(&uprobes_treelock);
> + down_read(&uprobes_treelock);
> n = find_node_in_range(inode, min, max);
> - spin_unlock(&uprobes_treelock);
> + up_read(&uprobes_treelock);
>
> return !!n;
> }
> @@ -2357,3 +2360,98 @@ void __init uprobes_init(void)
>
> BUG_ON(register_die_notifier(&uprobe_exception_nb));
> }
> +
> +#ifdef CONFIG_DEBUG_FS
> +
> +static void *uprobe_seq_start(struct seq_file *m, loff_t *pos)
> +{
> + loff_t num = *pos;
> + struct rb_node *rbp;
> +
> + down_read(&uprobes_treelock);
Is there a missing corresponding up_read?
Thanks,
Ian
> + for (rbp = rb_first(&uprobes_tree); rbp; rbp = rb_next(rbp)) {
> + if (num-- == 0)
> + return rbp;
> + }
> +
> + return NULL;
> +}
> +
> +static void *uprobe_seq_next(struct seq_file *f, void *v, loff_t *pos)
> +{
> + ++*pos;
> + return (void *)rb_next(v);
> +}
> +
> +static void uprobe_seq_stop(struct seq_file *f, void *v)
> +{
> + up_read(&uprobes_treelock);
> +}
> +
> +static int show_uprobe(struct seq_file *m, void *v)
> +{
> + struct uprobe *uprobe = rb_entry_safe(v, struct uprobe, rb_node);
> + struct uprobe_consumer *con;
> + char *modname, namebuf[KSYM_NAME_LEN];
> + const char *sym;
> + unsigned int cnt = 1;
> +
> + seq_printf(m, "inode+offset/ref_ctr_offset %lu+0x%llx/0x%llx\n",
> + uprobe->inode->i_ino, uprobe->offset, uprobe->ref_ctr_offset);
> + seq_printf(m, " ref %u\n",
> + refcount_read(&uprobe->ref));
> + seq_printf(m, " register_rwsem %s\n",
> + rwsem_is_locked(&uprobe->register_rwsem)?"(locked)":"(unlocked)");
> + seq_printf(m, " consumer_rwsem %s\n",
> + rwsem_is_locked(&uprobe->consumer_rwsem)?"(locked)":"(unlocked)");
> +
> + /* lock consumer_rwsem when hold uprobes_treelock */
> + down_read(&uprobe->consumer_rwsem);
> + for (con = uprobe->consumers; con; con = con->next, cnt++) {
> + seq_printf(m, " consumers-%u\n", cnt);
> +
> + modname = NULL;
> + sym = kallsyms_lookup((unsigned long)con->handler, NULL, NULL,
> + &modname, namebuf);
> + seq_printf(m, " handler 0x%px(%s) %s\n",
> + con->handler, (sym ? sym : " "), (modname ? modname : " "));
> +
> + modname = NULL;
> + sym = kallsyms_lookup((unsigned long)con->ret_handler, NULL, NULL,
> + &modname, namebuf);
> + seq_printf(m, " ret_handler 0x%px(%s) %s\n",
> + con->ret_handler, (sym ? sym : " "), (modname ? modname : " "));
> +
> + modname = NULL;
> + sym = kallsyms_lookup((unsigned long)con->filter, NULL, NULL,
> + &modname, namebuf);
> + seq_printf(m, " filter 0x%px(%s) %s\n",
> + con->filter, (sym ? sym : " "), (modname ? modname : " "));
> + }
> + up_read(&uprobe->consumer_rwsem);
> +
> + return 0;
> +}
> +
> +static const struct seq_operations uprobes_sops = {
> + .start = uprobe_seq_start,
> + .next = uprobe_seq_next,
> + .stop = uprobe_seq_stop,
> + .show = show_uprobe,
> +};
> +
> +DEFINE_SEQ_ATTRIBUTE(uprobes);
> +
> +static int __init debugfs_uprobe_init(void)
> +{
> + struct dentry *dir;
> +
> + dir = debugfs_create_dir("uprobes", NULL);
> +
> + debugfs_create_file("list", 0400, dir, NULL, &uprobes_fops);
> +
> + return 0;
> +}
> +late_initcall(debugfs_uprobe_init);
> +
> +#endif /* CONFIG_DEBUG_FS */
> --
> 2.38.1
>
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