// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
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#include <linux/perf_event.h>
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#include <linux/uaccess.h>
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/* Kernel callchain */
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struct stackframe {
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unsigned long fp;
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unsigned long lr;
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};
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static int unwind_frame_kernel(struct stackframe *frame)
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{
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unsigned long low = (unsigned long)task_stack_page(current);
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unsigned long high = low + THREAD_SIZE;
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if (unlikely(frame->fp < low || frame->fp > high))
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return -EPERM;
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if (kstack_end((void *)frame->fp) || frame->fp & 0x3)
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return -EPERM;
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*frame = *(struct stackframe *)frame->fp;
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if (__kernel_text_address(frame->lr)) {
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int graph = 0;
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frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr,
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NULL);
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}
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return 0;
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}
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static void notrace walk_stackframe(struct stackframe *fr,
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struct perf_callchain_entry_ctx *entry)
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{
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do {
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perf_callchain_store(entry, fr->lr);
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} while (unwind_frame_kernel(fr) >= 0);
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}
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/*
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* Get the return address for a single stackframe and return a pointer to the
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* next frame tail.
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*/
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static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
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unsigned long fp, unsigned long reg_lr)
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{
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struct stackframe buftail;
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unsigned long lr = 0;
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unsigned long __user *user_frame_tail = (unsigned long __user *)fp;
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/* Check accessibility of one struct frame_tail beyond */
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if (!access_ok(user_frame_tail, sizeof(buftail)))
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return 0;
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if (__copy_from_user_inatomic(&buftail, user_frame_tail,
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sizeof(buftail)))
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return 0;
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if (reg_lr != 0)
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lr = reg_lr;
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else
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lr = buftail.lr;
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fp = buftail.fp;
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perf_callchain_store(entry, lr);
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return fp;
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}
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/*
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* This will be called when the target is in user mode
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* This function will only be called when we use
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* "PERF_SAMPLE_CALLCHAIN" in
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* kernel/events/core.c:perf_prepare_sample()
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*
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* How to trigger perf_callchain_[user/kernel] :
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* $ perf record -e cpu-clock --call-graph fp ./program
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* $ perf report --call-graph
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*
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* On C-SKY platform, the program being sampled and the C library
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* need to be compiled with * -mbacktrace, otherwise the user
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* stack will not contain function frame.
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*/
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void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
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struct pt_regs *regs)
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{
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struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
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unsigned long fp = 0;
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/* C-SKY does not support virtualization. */
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if (guest_cbs && guest_cbs->is_in_guest())
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return;
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fp = regs->regs[4];
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perf_callchain_store(entry, regs->pc);
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/*
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* While backtrace from leaf function, lr is normally
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* not saved inside frame on C-SKY, so get lr from pt_regs
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* at the sample point. However, lr value can be incorrect if
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* lr is used as temp register
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*/
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fp = user_backtrace(entry, fp, regs->lr);
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while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
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fp = user_backtrace(entry, fp, 0);
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}
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void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
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struct pt_regs *regs)
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{
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struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
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struct stackframe fr;
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/* C-SKY does not support virtualization. */
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if (guest_cbs && guest_cbs->is_in_guest()) {
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pr_warn("C-SKY does not support perf in guest mode!");
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return;
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}
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fr.fp = regs->regs[4];
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fr.lr = regs->lr;
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walk_stackframe(&fr, entry);
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}
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