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Date: Fri, 09 Apr 2010 17:09:32 -0400
From: Masami Hiramatsu <mhiramat@...hat.com>
To: Jason Baron <jbaron@...hat.com>
CC: linux-kernel@...r.kernel.org, mingo@...e.hu,
mathieu.desnoyers@...ymtl.ca, hpa@...or.com, tglx@...utronix.de,
rostedt@...dmis.org, andi@...stfloor.org, roland@...hat.com,
rth@...hat.com, fweisbec@...il.com, avi@...hat.com
Subject: Re: [PATCH 9/9] jump label: jump_label_text_reserved() to reserve
our jump points
Jason Baron wrote:
> Add a jump_label_text_reserved(void *start, void *end), so that other
> pieces of code that want to modify kernel text, can first verify that
> jump label has not reserved the instruction.
>
> Signed-off-by: Jason Baron <jbaron@...hat.com>
Acked-by: Masami Hiramatsu <mhiramat@...hat.com>
At least kprobes parts. :)
Thank you,
> ---
> arch/x86/kernel/kprobes.c | 3 +-
> include/linux/jump_label.h | 6 +++
> kernel/jump_label.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
> kernel/kprobes.c | 3 +-
> 4 files changed, 93 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
> index b43bbae..87bcf63 100644
> --- a/arch/x86/kernel/kprobes.c
> +++ b/arch/x86/kernel/kprobes.c
> @@ -1194,7 +1194,8 @@ static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
> }
> /* Check whether the address range is reserved */
> if (ftrace_text_reserved(src, src + len - 1) ||
> - alternatives_text_reserved(src, src + len - 1))
> + alternatives_text_reserved(src, src + len - 1) ||
> + jump_label_text_reserved(src, src + len - 1))
> return -EBUSY;
>
> return len;
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index 7238805..90ca4b6 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -31,6 +31,7 @@ extern void arch_jump_label_transform(struct jump_entry *entry,
> enum jump_label_type type);
>
> extern void jump_label_update(const char *name, enum jump_label_type type);
> +extern int jump_label_text_reserved(void *start, void *end);
>
> extern void apply_jump_label_nops(struct module *mod);
>
> @@ -65,6 +66,11 @@ static inline int apply_jump_label_nops(struct module *mod)
> return 0;
> }
>
> +static inline int jump_label_text_reserved(void *start, void *end)
> +{
> + return 0;
> +}
> +
> #endif
>
> #endif
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index 7e7458b..24bba61 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -179,6 +179,89 @@ void jump_label_update(const char *name, enum jump_label_type type)
> mutex_unlock(&jump_label_mutex);
> }
>
> +static int addr_conflict(struct jump_entry *entry, void *start, void *end)
> +{
> + if (entry->code <= (unsigned long)end &&
> + entry->code + IDEAL_NOP_SIZE_5 > (unsigned long)start)
> + return 1;
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_MODULES
> +
> +static int module_conflict(void *start, void *end)
> +{
> + struct hlist_head *head;
> + struct hlist_node *node, *node_next, *module_node, *module_node_next;
> + struct jump_label_entry *e;
> + struct jump_label_module_entry *e_module;
> + struct jump_entry *iter;
> + int i, count;
> + int conflict = 0;
> +
> + for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
> + head = &jump_label_table[i];
> + hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
> + hlist_for_each_entry_safe(e_module, module_node,
> + module_node_next,
> + &(e->modules), hlist) {
> + count = e_module->nr_entries;
> + iter = e_module->table;
> + while (count--) {
> + if (addr_conflict(iter, start, end)) {
> + conflict = 1;
> + goto out;
> + }
> + iter++;
> + }
> + }
> + }
> + }
> +out:
> + return conflict;
> +}
> +
> +#endif
> +
> +/***
> + * jump_label_text_reserved - check if addr range is reserved
> + * @start: start text addr
> + * @end: end text addr
> + *
> + * checks if the text addr located between @start and @end
> + * overlaps with any of the jump label patch addresses. Code
> + * that wants to modify kernel text should first verify that
> + * it does not overlap with any of the jump label addresses.
> + *
> + * returns 1 if there is an overlap, 0 otherwise
> + */
> +int jump_label_text_reserved(void *start, void *end)
> +{
> + struct jump_entry *iter;
> + struct jump_entry *iter_start = __start___jump_table;
> + struct jump_entry *iter_stop = __start___jump_table;
> + int conflict = 0;
> +
> + mutex_lock(&jump_label_mutex);
> + iter = iter_start;
> + while (iter < iter_stop) {
> + if (addr_conflict(iter, start, end)) {
> + conflict = 1;
> + goto out;
> + }
> + iter++;
> + }
> +
> + /* now check modules */
> +#ifdef CONFIG_MODULES
> + conflict = module_conflict(start, end);
> +#endif
> +out:
> + mutex_unlock(&jump_label_mutex);
> + return conflict;
> +}
> +
> static int init_jump_label(void)
> {
> int ret;
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index fa034d2..a57755f 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1140,7 +1140,8 @@ int __kprobes register_kprobe(struct kprobe *p)
> preempt_disable();
> if (!kernel_text_address((unsigned long) p->addr) ||
> in_kprobes_functions((unsigned long) p->addr) ||
> - ftrace_text_reserved(p->addr, p->addr)) {
> + ftrace_text_reserved(p->addr, p->addr) ||
> + jump_label_text_reserved(p->addr, p->addr)) {
> preempt_enable();
> return -EINVAL;
> }
--
Masami Hiramatsu
e-mail: mhiramat@...hat.com
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