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    Subject[tip:perf/core] jump label: Add jump_label_text_reserved() to reserve jump points
    Commit-ID:  4c3ef6d79328c0e23ade60cbfc8d496123a6855c
    Gitweb: http://git.kernel.org/tip/4c3ef6d79328c0e23ade60cbfc8d496123a6855c
    Author: Jason Baron <jbaron@redhat.com>
    AuthorDate: Fri, 17 Sep 2010 11:09:08 -0400
    Committer: Steven Rostedt <rostedt@goodmis.org>
    CommitDate: Wed, 22 Sep 2010 16:30:46 -0400

    jump label: Add jump_label_text_reserved() to reserve jump points

    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.

    Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
    Signed-off-by: Jason Baron <jbaron@redhat.com>
    LKML-Reference: <06236663a3a7b1c1f13576bb9eccb6d9c17b7bfe.1284733808.git.jbaron@redhat.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    arch/x86/kernel/kprobes.c | 3 +-
    include/linux/jump_label.h | 8 ++++-
    kernel/jump_label.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
    kernel/kprobes.c | 3 +-
    4 files changed, 94 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
    index e05952a..1cbd54c 100644
    --- a/arch/x86/kernel/kprobes.c
    +++ b/arch/x86/kernel/kprobes.c
    @@ -1218,7 +1218,8 @@ 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 de58656..b72cd9f 100644
    --- a/include/linux/jump_label.h
    +++ b/include/linux/jump_label.h
    @@ -20,9 +20,10 @@ extern struct jump_entry __stop___jump_table[];

    extern void arch_jump_label_transform(struct jump_entry *entry,
    enum jump_label_type type);
    +extern void arch_jump_label_text_poke_early(jump_label_t addr);
    extern void jump_label_update(unsigned long key, enum jump_label_type type);
    extern void jump_label_apply_nops(struct module *mod);
    -extern void arch_jump_label_text_poke_early(jump_label_t addr);
    +extern int jump_label_text_reserved(void *start, void *end);

    #define enable_jump_label(key) \
    jump_label_update((unsigned long)key, JUMP_LABEL_ENABLE);
    @@ -53,6 +54,11 @@ static inline int jump_label_apply_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 460fd40..7be868b 100644
    --- a/kernel/jump_label.c
    +++ b/kernel/jump_label.c
    @@ -177,6 +177,89 @@ void jump_label_update(unsigned long key, 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 + JUMP_LABEL_NOP_SIZE > (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 __init int init_jump_label(void)
    {
    int ret;
    diff --git a/kernel/kprobes.c b/kernel/kprobes.c
    index 18904e4..ec4210c 100644
    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -1147,7 +1147,8 @@ 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;
    }

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