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    SubjectRe: [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@redhat.com>

    Acked-by: Masami Hiramatsu <mhiramat@redhat.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@redhat.com


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