// 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 ra;
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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_ra)
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{
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struct stackframe buftail;
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unsigned long ra = 0;
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unsigned long __user *user_frame_tail =
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(unsigned long __user *)(fp - sizeof(struct stackframe));
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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_ra != 0)
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ra = reg_ra;
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else
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ra = buftail.ra;
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fp = buftail.fp;
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if (ra != 0)
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perf_callchain_store(entry, ra);
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else
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return 0;
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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 RISC-V platform, the program being sampled and the C library
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* need to be compiled with -fno-omit-frame-pointer, otherwise
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* the user 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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/* RISC-V does not support perf in guest mode. */
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if (guest_cbs && guest_cbs->is_in_guest())
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return;
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fp = regs->s0;
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perf_callchain_store(entry, regs->epc);
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fp = user_backtrace(entry, fp, regs->ra);
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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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bool fill_callchain(unsigned long pc, void *entry)
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{
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return perf_callchain_store(entry, pc) == 0;
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}
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void notrace walk_stackframe(struct task_struct *task,
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struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);
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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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/* RISC-V does not support perf in guest mode. */
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if (guest_cbs && guest_cbs->is_in_guest()) {
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pr_warn("RISC-V does not support perf in guest mode!");
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return;
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}
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walk_stackframe(NULL, regs, fill_callchain, entry);
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}
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