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    Subject[tip: perf/kprobes] csky: kprobes: Use generic kretprobe trampoline handler
    The following commit has been merged into the perf/kprobes branch of tip:

    Commit-ID: 03c8a4a447008c1a755cd32bc89af24119bd08f1
    Gitweb: https://git.kernel.org/tip/03c8a4a447008c1a755cd32bc89af24119bd08f1
    Author: Masami Hiramatsu <mhiramat@kernel.org>
    AuthorDate: Sat, 29 Aug 2020 22:00:58 +09:00
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitterDate: Tue, 08 Sep 2020 11:52:33 +02:00

    csky: kprobes: Use generic kretprobe trampoline handler

    Use the generic kretprobe trampoline handler. Don't use
    framepointer verification.

    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Acked-by: Guo Ren <guoren@kernel.org>
    Link: https://lore.kernel.org/r/159870605775.1229682.2627276871589951304.stgit@devnote2
    ---
    arch/csky/kernel/probes/kprobes.c | 77 +------------------------------
    1 file changed, 2 insertions(+), 75 deletions(-)

    diff --git a/arch/csky/kernel/probes/kprobes.c b/arch/csky/kernel/probes/kprobes.c
    index f0f733b..589f090 100644
    --- a/arch/csky/kernel/probes/kprobes.c
    +++ b/arch/csky/kernel/probes/kprobes.c
    @@ -404,87 +404,14 @@ int __init arch_populate_kprobe_blacklist(void)

    void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
    {
    - struct kretprobe_instance *ri = NULL;
    - struct hlist_head *head, empty_rp;
    - struct hlist_node *tmp;
    - unsigned long flags, orig_ret_address = 0;
    - unsigned long trampoline_address =
    - (unsigned long)&kretprobe_trampoline;
    - kprobe_opcode_t *correct_ret_addr = NULL;
    -
    - INIT_HLIST_HEAD(&empty_rp);
    - kretprobe_hash_lock(current, &head, &flags);
    -
    - /*
    - * It is possible to have multiple instances associated with a given
    - * task either because multiple functions in the call path have
    - * return probes installed on them, and/or more than one
    - * return probe was registered for a target function.
    - *
    - * We can handle this because:
    - * - instances are always pushed into the head of the list
    - * - when multiple return probes are registered for the same
    - * function, the (chronologically) first instance's ret_addr
    - * will be the real return address, and all the rest will
    - * point to kretprobe_trampoline.
    - */
    - hlist_for_each_entry_safe(ri, tmp, head, hlist) {
    - if (ri->task != current)
    - /* another task is sharing our hash bucket */
    - continue;
    -
    - orig_ret_address = (unsigned long)ri->ret_addr;
    -
    - if (orig_ret_address != trampoline_address)
    - /*
    - * This is the real return address. Any other
    - * instances associated with this task are for
    - * other calls deeper on the call stack
    - */
    - break;
    - }
    -
    - kretprobe_assert(ri, orig_ret_address, trampoline_address);
    -
    - correct_ret_addr = ri->ret_addr;
    - hlist_for_each_entry_safe(ri, tmp, head, hlist) {
    - if (ri->task != current)
    - /* another task is sharing our hash bucket */
    - continue;
    -
    - orig_ret_address = (unsigned long)ri->ret_addr;
    - if (ri->rp && ri->rp->handler) {
    - __this_cpu_write(current_kprobe, &ri->rp->kp);
    - get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
    - ri->ret_addr = correct_ret_addr;
    - ri->rp->handler(ri, regs);
    - __this_cpu_write(current_kprobe, NULL);
    - }
    -
    - recycle_rp_inst(ri, &empty_rp);
    -
    - if (orig_ret_address != trampoline_address)
    - /*
    - * This is the real return address. Any other
    - * instances associated with this task are for
    - * other calls deeper on the call stack
    - */
    - break;
    - }
    -
    - kretprobe_hash_unlock(current, &flags);
    -
    - hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
    - hlist_del(&ri->hlist);
    - kfree(ri);
    - }
    - return (void *)orig_ret_address;
    + return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
    }

    void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
    struct pt_regs *regs)
    {
    ri->ret_addr = (kprobe_opcode_t *)regs->lr;
    + ri->fp = NULL;
    regs->lr = (unsigned long) &kretprobe_trampoline;
    }

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